Deep Dreams of a CNN trained on MNIST data – II – some code for pattern carving

In the last article of this series

Deep Dreams of a CNN trained on MNIST data – I – a first approach based on one selected map of a convolutional layer

I presented some “Deep Dream” images of a CNN trained on MNIST data. Although one cannot produce spectacular images with a simple CNN based on gray scale, low resolution image data, we still got a glimpse of what the big guys do with more advanced CNNs and image data. But we have only started, yet ….

In the forthcoming articles we shall extend our abilities step by step beyond the present level. Our next goal is to work on different length scales within the image, i.e. we go down into sub-tiles of the original image, analyze the sub-structures there and include the results in the CNN’s dreams. But first we need to understand more precisely how we apply the image manipulation techniques that “carve” some additional dream-like optical elements, which correspond to map triggering features, into an arbitrary input image presented to the CNN.

Carving: A combination of low-resolution OIP-pattern creation and a reproduction of high-resolution details

I used the term “carved” intentionally. Artists or craftsmen who create little figures or faces out of wooden blocks by a steady process of carving often say that they only bring to the surface what already was there – namely in the basic fiber structures of the wood. Well, the original algorithm for the creation of pure OIP- or feature patterns systematically amplifies some minimal correlated pixel “structures” detected in an input image with random pixel values. The values of all other pixels outside the OIP pattern are reduced; sooner or later they form a darker and rather homogeneous background. The “detection” is based on (trained) filters which react to certain pixel constellations. We already encoded an adaption of a related method for CNN filter visualization, which Francois Chollet discusses in his book on “Deep learning with Python”, into a Python class in another article series of this blog (see the link section at the end of this article).

There is, however, a major difference regarding our present context: During the image manipulations for the visualization of Deep Dreams we do not want to remove all details of the original image presented to the DeepDream algorithm. Instead, we just modify it at places where the CNN detects traces of patterns which trigger a strong response of one or multiple maps of our CNN – and keep detail information alive elsewhere. I.e., we must counterbalance the tendency of our OIP algorithm to level out information outside the OIP structures.

How do we do this, when both our present OIP algorithm and the MNIST-trained CNN are limited to a resolution of (28×28) pixels, only?

Carving – amplification of certain OIP structures and intermittent replenishment of details of the original image

In this article we follow the simple strategy explained in the last article:

  • Preparation:
    • We choose a map.
    • We turn the colored original input image (about which the CNN shall dream) into a gray one.
    • We downscale the original image to a size of (28×28) by interpolation, upscale the result again by interpolating again (with loss) and calculate the difference to the original full resolution image (all interpolations done in a bicubic way). (The difference contains information on detail structures.)
  • Loop (4 times or so):
    • We apply the OIP-algorithm on the downscaled input image for a fixed amount of epochs with a small epsilon.
      The result is a slight emphasis of
      pixel structures resembling OIP patterns.
    • We upscale the result by bicubic interpolation to the original size.
    • We re-add the difference to the original image, i.e. we supply details again.
    • We downscale the result again.
  • Eventual image optimization: We apply some contrast treatment to the resulting image, whose pixel value range and distribution has gradually been changed in comparison to the original image.

This corresponds to a careful accentuation of an OIP-pattern detected by a certain map in the given structured pixel data of the input image (on coarse scales) – without loosing all details of the initial image. As said – it resembles a process of carving coarse patterns into the original image ..

Note: The above algorithm works on the whole image – a modified version working on a variety of smaller length scales is discussed in further articles.

What does this strategy look like in Python statements for Jupyter cells?

Start with loading required modules and involving your graphics card

We have to load python modules to support our CNN, the OIP algorithm and some plotting. In a second step we need to invoke the graphics card. This is done in two Jupyter cells (1 and 2). Their content was already described in the article

A simple CNN for the MNIST dataset – XI – Python code for filter visualization and OIP detection

of a parallel series in this blog. These initial steps are followed by an instantiation of a class “My_OIP” containing all required methods. The __init__() function of this class restores a Keras model of our basic CNN from a h5-file:

Jupyter cell 3

%matplotlib inline

# Load the CNN-model 
#  ~~~~~~~~~~~~~~~~~
imp.reload(myOIP)
try:
    with tf.device("/GPU:0"):
        MyOIP = myOIP.My_OIP(cnn_model_file = 'cnn_best.h5', layer_name = 'Conv2D_3')

except SystemExit:
    print("stopped")
    

Turn the original image into a gray one, downscale it and calculate difference-tensors for coarsely re-enlarged versions

In the next Jupyter cell we deal with the following initial image:

We choose a method (out of 3) to turn it into a gray scaled image. Afterwards we calculate the difference between an image tensor of the original (gray) image and a coarse, but softly rescaled image derived from a (28×28)-pixel version.

Jupyter cell 4

# Down-, gray- and Re-scale images, determine correction differences  
# *******************************************************************
import PIL
from PIL import Image, ImageOps

fig_size = plt.rcParams["figure.figsize"]
fig_size[0] = 15
fig_size[1] = 30
fig_1 = plt.figure(1)
ax1_1 = fig_1.add_subplot(531)
ax1_2 = fig_1.add_subplot(532)
ax1_3 = fig_1.add_subplot(533)
ax2_1 = fig_1.add_subplot(534)
ax2_2 = fig_1.add_subplot(535)
ax2_3 = fig_1.add_subplot(536)
ax3_1 = fig_1.add_subplot(537)
ax3_2 = fig_1.add_subplot(538)
ax3_3 = fig_1.add_subplot(539)
ax4_1 = fig_1.add_subplot(5,3,10)
ax4_2 = fig_1.add_subplot(5,3,11)
ax4_3 = fig_1.add_subplot(5,3,12)

# Parameters 
# ************
# size of the image to work with 
img_wk_size = 560 
# method to turn the original picture into a gray scaled one 
gray_scaling_
method = 2

# bring the orig img down to (560, 560) 
# ***************************************
imgvc    = Image.open("rosen_orig_farbe.jpg")
imgvc_g  = imgvc.convert("L")

# downsize with PIL 
# ******************
imgvc_wk_size    = imgvc.resize((img_wk_size,img_wk_size), resample=PIL.Image.BICUBIC)
imgvc_wk_size_g  = imgvc_wk_size.convert("L")
imgvc_28      = imgvc.resize(  (28,28), resample=PIL.Image.BICUBIC)
imgvc_g_28    = imgvc_g.resize((28,28), resample=PIL.Image.BICUBIC)

# Change to np array
ay_picc = np.array(imgvc_wk_size)

# Display orig and wk_size images  
# *********************************
ax1_1.imshow(imgvc)
ax1_2.imshow(imgvc_wk_size)
ax1_3.imshow(imgvc_g, cmap=plt.cm.gray)

# Apply 3 different methods to turn the image into a gray one 
# **************************************************************
#Red * 0.3 + Green * 0.59 + Blue * 0.11
#Red * 0.2126 + Green * 0.7152 + Blue * 0.0722
#Red * 0.299 + Green * 0.587 + Blue * 0.114

ay_picc_g1 = ( 0.3    * ay_picc[:,:,0] + 0.59   * ay_picc[:,:,1] + 0.11   * ay_picc[:,:,2] )  
ay_picc_g2 = ( 0.299  * ay_picc[:,:,0] + 0.587  * ay_picc[:,:,1] + 0.114  * ay_picc[:,:,2] )  
ay_picc_g3 = ( 0.2126 * ay_picc[:,:,0] + 0.7152 * ay_picc[:,:,1] + 0.0722 * ay_picc[:,:,2] )  

ay_picc_g1 = ay_picc_g1.astype('float32') 
ay_picc_g2 = ay_picc_g2.astype('float32') 
ay_picc_g3 = ay_picc_g3.astype('float32') 

# Prepare tensors
# *****************
t_picc_g1 = ay_picc_g1.reshape((1, img_wk_size, img_wk_size, 1))
t_picc_g2 = ay_picc_g2.reshape((1, img_wk_size, img_wk_size, 1))
t_picc_g3 = ay_picc_g3.reshape((1, img_wk_size, img_wk_size, 1))

t_picc_g1 = tf.image.per_image_standardization(t_picc_g1)
t_picc_g2 = tf.image.per_image_standardization(t_picc_g2)
t_picc_g3 = tf.image.per_image_standardization(t_picc_g3)

# Display gray-tensor variants    
# ****************************
ax2_1.imshow(t_picc_g1[0,:,:,0], cmap=plt.cm.gray)
ax2_2.imshow(t_picc_g2[0,:,:,0], cmap=plt.cm.gray)
ax2_3.imshow(t_picc_g3[0,:,:,0], cmap=plt.cm.gray)

# choose one gray img
# ******************
if   gray_scaling_method == 1:
    t_picc_g = t_picc_g1
elif gray_scaling_method == 2:
    t_picc_g = t_picc_g2
else:
    t_picc_g = t_picc_g3

# downsize to (28,28) and standardize
# *****************************************
t_picc_g_28_scd  = tf.image.resize(t_picc_g, [28,28], method="bicubic", antialias=True)
t_picc_g_28_std  = tf.image.per_image_standardization(t_picc_g_28_scd)
t_picc_g_28      = t_picc_g_28_std

# display 
ax3_1.imshow(imgvc_g_28, cmap=plt.cm.gray)
ax3_2.imshow(t_picc_g_28_scd[0,:,:,0], cmap=plt.cm.gray)
ax3_3.imshow(t_picc_g_28_std[0,:,:,0], cmap=plt.cm.gray)

# Upscale and get correction values  
# **********************************
t_picc_g_wk_size_scd     = tf.image.resize(t_picc_g_28, [img_wk_size,img_wk_size], method="bicubic", antialias=True)
t_picc_g_wk_size_scd_std = tf.image.per_image_standardization(t_picc_g_wk_size_scd)
t_picc_g_wk_size_corr    =  t_picc_g - t_picc_g_wk_size_scd_std   

# Correct and display 
# **********************
t_picc_g_wk_size_re   = t_picc_g_wk_size_scd_std + t_picc_g_wk_size_corr 
# Display
ax4_1.imshow(t_picc_g_wk_size_scd_std[0,:,:,0], cmap=plt.cm.gray)
ax4_2.imshow(t_picc_g[0,:,:,0],                 cmap=plt.cm.gray)
ax4_3.imshow(t_picc_g_wk_size_re[0,:,:,0],      cmap=plt.cm.gray)

 
The code is straightforward – a lot of visualization steps will later on just show tiny differences. For production you may shorten the code significantly.

In a first step we downscale the image to a work-size of (560×560) px with the help of PIL modules. (Note that 560 can be divided by 2, 4, 8, 16, 28). We then test out three methods to turn the image into a gray one. This step is required, because our MNIST-oriented CNN is trained for gray images, only. We
reshape the image data arrays to prepare for tensor-operations and standardize with the help of Tensorflow – and produce image tensors on the fly. Afterwards, we downscale to a size of (28×28) pixels; this is the size of the MNIST images for which the CNN has been trained. We upscale to the work-size again, compare it to the original detailed image and calculate respective differences of the tensor-components. These differences will later be used to re-add details to our manipulated images.

The following picture displays the resulting output:

Note: The last two images should not show any difference. The middle row and the displays how coarse the (28×28) resolution really is and how much information we have lost after upscaling to (560×560)px.

OIP-Carving and detail replenishment

We now follow the algorithm described above. This leads to a main loop with steps for downscaling, OIP-carving on the (28×28)-scale, upscaling and a supplementation of original details:

Jupyter cell 5

# **************************************************+
# OIP analysis (to be used after the previous cell)
# **************************************************+

# Prepare plotting 
# -------------------
#interactive plotting 
#%matplotlib notebook 
#plt.ion()

fig_size = plt.rcParams["figure.figsize"]
fig_size[0] = 15
fig_size[1] = 25
fig_2 = plt.figure(2)
ax2_1_1 = fig_2.add_subplot(531)
ax2_1_2 = fig_2.add_subplot(532)
ax2_1_3 = fig_2.add_subplot(533)
ax2_2_1 = fig_2.add_subplot(534)
ax2_2_2 = fig_2.add_subplot(535)
ax2_2_3 = fig_2.add_subplot(536)
ax2_3_1 = fig_2.add_subplot(537)
ax2_3_2 = fig_2.add_subplot(538)
ax2_3_3 = fig_2.add_subplot(539)
ax2_4_1 = fig_2.add_subplot(5,3,10)
ax2_4_2 = fig_2.add_subplot(5,3,11)
ax2_4_3 = fig_2.add_subplot(5,3,12)

fig_size = plt.rcParams["figure.figsize"]
fig_size[0] = 16
fig_size[1] = 8
fig_3 = plt.figure(3)
axa_1 = fig_3.add_subplot(241)
axa_2 = fig_3.add_subplot(242)
axa_3 = fig_3.add_subplot(243)
axa_4 = fig_3.add_subplot(244)
axa_5 = fig_3.add_subplot(245)
axa_6 = fig_3.add_subplot(246)
axa_7 = fig_3.add_subplot(247)
axa_8 = fig_3.add_subplot(248)
li_axa = [axa_1, axa_2, axa_3, axa_4, axa_5, axa_6, axa_7, axa_8]

fig_size = plt.rcParams["figure.figsize"]
fig_size[0] = 16
fig_size[1] = 4
fig_h = plt.figure(50)
ax_h_1 = fig_h.add_subplot(141)
ax_h_2 = fig_h.add_subplot(142)
ax_h_3 = fig_h.add_subplot(143)
ax_h_4 = fig_h.add_subplot(144)
li_axa = [axa_1, axa_2, axa_3, axa_4, axa_5, axa_6, axa_7, axa_8]

# list for img tensors 
li_t_imgs = []

# Parameters for the OIP run
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
map_index = 56         # map-index we are interested in 
# map_index = -1         # for this value the whole layer is taken; the loss function is averaged over the maps
n_epochs  = 20          # should be divisible by 5  
n_steps   = 6           # number of intermediate reports 
epsilon   = 0.01        # step size for gradient correction  
conv_criterion = 2.e-4  # criterion for a potential stop of optimization 

n_iter    = 5           # number of iterations for down-, upscaling and supplementation of details

# Initial image
# -----------------
MyOIP._initial_inp_img_data = t_picc_g_28

# Main iteration loop 
# ***********************
for i in range(n_iter): 

    # Perform the OIP analysis 
    MyOIP._derive_OIP(map_index = map_index, 
                      n_epochs = n_epochs, n_steps = n_steps, 
       
               epsilon = epsilon , conv_criterion = conv_criterion, 
                      b_stop_with_convergence=False,
                      b_print = False,
                      li_axa = li_axa,
                      ax1_1 = ax2_1_1, ax1_2 = ax2_1_2,
                      centre_move = 0.33, fact = 1.0)

    t_oip_c_g_28  = MyOIP._inp_img_data
    ay_oip_c_g_28 = t_oip_c_g_28[0,:,:,0].numpy()

    ay_oip_c_g_28_cont = MyOIP._transform_tensor_to_img(T_img=t_oip_c_g_28[0,:,:,0], centre_move=0.33, fact=1.0)
    ax2_1_3.imshow(ay_oip_c_g_28_cont, cmap=plt.cm.gray)

    # Rescale to 500
    t_oip_c_g_wk_size  = tf.image.resize(t_oip_c_g_28, [img_wk_size,img_wk_size], method="bicubic", antialias=True)
    #t_oip_c_g_500 = tf.image.per_image_standardization(t_oip_c_g_500)

    t_oip_c_g_wk_size_re     = t_oip_c_g_wk_size + t_picc_g_wk_size_corr 
    t_oip_c_g_wk_size_re_std = tf.image.per_image_standardization(t_oip_c_g_wk_size_re)

    # remember the img tensors of the iterations    
    li_t_imgs.append(t_oip_c_g_wk_size_re_std)
    
    # do not change the gray spectrum for iterations 
    MyOIP._initial_inp_img_data = tf.image.resize(t_oip_c_g_wk_size_re_std, [28,28], method="bicubic", antialias=True)
    
    # Intermediate plotting - if required and if plt.ion() is set 
    # ------------------------
    if b_plot_intermediate and j < n_iter-1: 
        ay_oip_c_g_wk_size = t_oip_c_g_wk_size[0,:,:,0].numpy()
        #display OIPs
        ax2_2_1.imshow(t_picc_g_28[0,:,:,0], cmap=plt.cm.gray)
        ax2_2_2.imshow(ay_oip_c_g_28,  cmap=plt.cm.gray)
        ax2_2_3.imshow(ay_oip_c_g_wk_size, cmap=plt.cm.gray)

        ax2_3_1.imshow(t_oip_c_g_wk_size[0,:,:,0], cmap=plt.cm.gray)
        ax2_3_2.imshow(t_oip_c_g_wk_size_re[0,:,:,0], cmap=plt.cm.gray)
        ax2_3_3.imshow(t_picc_g[0,:,:,0], cmap=plt.cm.gray)
    
        # modify the gray spectrum for plotting - cut off by clipping to limit the extend of the gray color map  
        min1 = tf.reduce_min(t_picc_g)
        min2 = tf.reduce_min(t_oip_c_g_wk_size_re)
        max1 = tf.reduce_max(t_picc_g)
        max2 = tf.reduce_max(t_oip_c_g_wk_size_re)
        # tf.print("min1 = ", min1, " :: min2 = ", min2, " :: max1 = ", max1, " :: max2 = ", max2 )

        #fac1 = min2/min1 * 0.95
        #fac2 = 1.0*fac1
        fac2 = 1.18
        fac3 = 0.92
        cut_lft = fac3*min1
        cut_rht = fac3*max1
        cut_rht = fac3*abs(min1)
        tf.print("cut_lft = ", cut_lft, "  cut_rht = ", cut_rht)

        t_oip_c_g_wk_size_re_std_plt = fac2 * t_oip_c_g_wk_size_re_std 
        t_oip_c_g_wk_size_re_std_plt = tf.clip_by_value(t_oip_c_g_wk_size_re_std_plt, cut_lft, cut_rht)
    
        ax2_4_1.imshow(t_oip_c_g_wk_size[0,:,:,0], cmap=plt.cm.gray)
        ax2_4_2.imshow(t_oip_c_g_wk_size_re_std[0,:,:,0], cmap=plt.cm.gray)
        ax2_4_3.imshow(t_oip_c_g_wk_size_re_std_plt[0,:,:,0], cmap=plt.cm.gray)


# Eventual plotting 
# ********************
ay_oip_c_g_wk_size = t_oip_c_g_wk_size[0,:,:,0].numpy()

#display OIPs
ax2_2_1.imshow(t_picc_g_28[0,:,:,0], cmap=plt.cm.gray)
ax2_2_2.imshow(ay_oip_c_g_28,  cmap=plt.cm.gray)
ax2_2_3.imshow(ay_oip_c_g_wk_size, cmap=plt.cm.gray)

ax2_3_1.imshow(t_oip_c_g_wk_size[0,:,:,0], cmap=plt.cm.gray)
ax2_3_2.imshow(t_oip_c_g_wk_size_re[0,:,:,0], cmap=plt.cm.gray)
ax2_3_3.imshow(t_picc_g[0,:,:,0], cmap=plt.cm.gray)

# modify the gray spectrum for plotting - cut off by clipping to limit the extend of the gray color map  
min1 = tf.reduce_min(t_picc_g)
min2 = tf.reduce_min(t_oip_c_g_wk_size_re)
max1 = tf.reduce_max(t_picc_g)
max2 = tf.reduce_max(t_oip_c_g_wk_size_re)
# tf.print("min1 = ", min1, " :: min2 = ", min2, " :: max1 = ", max1, " :: max2 = ", max2 )

#fac1 = min2/min1 * 0.95
#fac2 = 1.0*fac1
fac2 = 1.10
fac3 = 0.92
cut_lft = fac3*min1
cut_rht = fac3*
max1
#cut_rht = fac3*abs(min1)
tf.print("cut_lft = ", cut_lft, "  cut_rht = ", cut_rht)

t_oip_c_g_wk_size_re_std_plt = fac2 * t_oip_c_g_wk_size_re_std 
t_oip_c_g_wk_size_re_std_plt = tf.clip_by_value(t_oip_c_g_wk_size_re_std_plt, cut_lft, cut_rht)

ax2_4_1.imshow(t_oip_c_g_wk_size[0,:,:,0], cmap=plt.cm.gray)
ax2_4_2.imshow(t_oip_c_g_wk_size_re_std[0,:,:,0], cmap=plt.cm.gray)
ax2_4_3.imshow(t_oip_c_g_wk_size_re_std_plt[0,:,:,0], cmap=plt.cm.gray)
    
# Histogram analysis and plotting 
# *********************************    
# prepare the histograms of greay values for the saved imagetensors     
ay0 = np.sort( t_picc_g[0, :, :, 0].numpy().ravel() )
ay1 = np.sort( li_t_imgs[0][0,:,:,0].numpy().ravel() )
ay2 = np.sort( li_t_imgs[1][0,:,:,0].numpy().ravel() )
ay3 = np.sort( li_t_imgs[2][0,:,:,0].numpy().ravel() )
ay4 = np.sort( li_t_imgs[3][0,:,:,0].numpy().ravel() )
#print(ay1)

nx, binsx, patchesx = ax_h_1.hist(ay0, bins='auto')
nx, binsx, patchesx = ax_h_2.hist(ay2, bins='auto')
nx, binsx, patchesx = ax_h_3.hist(ay3, bins='auto')
nx, binsx, patchesx = ax_h_4.hist(ay4, bins='auto')

 

We first prepare some Matplotlib axes frames. Note that the references should be clearly distinguishable and unique across the cells of the Jupyter notebook.

Parameters
Then we define parameters for a DeepDream run. [The attentive reader has noticed that I now allow for a value of nmap_index = -1. This corresponds to working with a loss function calculated and averaged over all maps (nmap=-1) of a layer. The changed code of the class My_OIP is given at the end of the article. We come back to this option in a later post of this series. For the time being we just work with a chosen single map and its cost function.]

The most interesting parameters are “n_epochs” and “n_iter“. These parameters help to tune a careful balance between OIP-“carving” and “detail replenishment”. These are parameters you absolutely should experiment with!

Iterations
We first pick the (28×28) gray image prepared in the previous Jupyter cell as the initial image presented to the CNN’s input layer. We then start an iteration by invoking the “My_OIP” class discussed in the article named above. (The parameters “centre_move = 0.33” and “fact = 1.0” refer to an image manipulation, namely a contrast enhancement.)
After OIP-carving over the chosen limited number of epochs we apply a special treatment to the data for the OPI-image derived so far. In a side step we enhance the contrast contrast for displaying the intermediate results. We then rescale by bicubic interpolation from 28×28 to the working size 560×560, add the prepared correction data and standardize. We add the results to a list for a later histogram analysis.

The preparation of plotting (of an intermediate and eventual image) comprises a step to reduce the spectrum of pixel values. This step is required as the iterative image manipulation leads to an extension of the maximum and the minimum values, i.e. the flanks of the value spectrum, up to a factor of 1.7 – although we only find a few pixels in that extended range. If we applied a standard gray-scale color map to the whole wider range of values then we would get a strong reduction in contrast – for the sake of including some extreme pixel values. The remedy is to cut the spectrum off at the original maximum/minimum value.

The histogram analysis performed at the end in addition shows that the central spectrum has become a bit narrower – we can compensate this by some factors fac2 and fac3. Play around with them.

Results of the carving process

Results for map 57 are displayed in the following image:

The effect of the “carving” is clearly visible as an overlayed ghost like pattern apparition. Standardization of the final images makes no big difference – however, the discussed compensation for the widened spectrum of the eventual image is important.

The histogram analysis shows the flank widening and the narrowing of the central core of the pixel value spectrum:

The following image allow a comparison of the original gray image with the carved image for parameters [n_epochs=20, n_iter=5]:

Conclusion

Deep Dreams are based on special image analysis and manipulation techniques. We adapted some of the techniques discussed in literature for high resolution images and advanced CNNs in a special way and for a single deep layer map of a low resolution CNN. We called the required intermittent combination of down- and upscaling, enhancing OIP-patterns and re-adding details “carving“. This helped us to create a “dream” of a CNN – which was trained with a bunch low resolution MNIST images, only; the dream can be based on arbitrary quadratic input images (here: an image of a bunch of roses).

The technique presented in this article can be extended to include a pattern analysis on various sub-parts and length-scales of the original image. In the next blog post we shall have a look at some of the required programming steps.

My_OIP class – V0.65

I have modified the My_OIP code a bit since the last articles on CNNs. You find the new version below.

 
'''
Module to create OIPs as visualizations of filters of a simple CNN for the MNIST data set
@version: 0.65, 12.12.2020
@change: V0.5:  was based on version 0.4 which was originally created in Jupyter cells
@change: V0.6: General revision of class "my_OIP" and its methods
@change: V0.6: Changes to the documentation 
@change: V0.65: Added intermediate plotting of selected input fluctuation patterns 
@attention: General status: For experimental purposes only! 
@requires: A full CNN trained on MNIST data 
@requires: A Keras model of the CNN and weight data saved in a h5-file, e.g."cnn_MIST_best.h5". 
           This file must be placed in the main directory of the Jupyter notebooks.
@requires: A Jupyter environment - from where the class My_OIP is called and where plotting takes place 
@note: The description to the interface to the class via the __init__()-method may be incomplete
@note: The use of prefixes li_ and ay_ is not yet consistent. ay_ should indicate numpy arrays, li_ instead normal Python lists
@warning: This version has not been tested outside a Jupyter environment - plotting in GTK/Qt-environment may require substantial changes 
@status: Under major development with frequent changes 
@author: Dr. Ralph Mönchmeyer
@copyright: Simplified BSD License, 12.12.2020. Copyright (c) 2020, Dr. Ralph Moenchmeyer, Augsburg, Germany

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and 
the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
'''

# Modules to be imported - these libs must be imported in a Jupyter cell nevertheless 
# ~~~~~~~~~~~~~~~~~~~~~~~~
import time 
import sys 
import math
import os 
from os import path as path

import numpy as np
from numpy import save  # used to export intermediate data
from numpy import load

import scipy
from sklearn.preprocessing import StandardScaler
from itertools import product 

import tensorflow as tf
from tensorflow import keras as K
from tensorflow.python.keras import backend as B  # this is the only version compatible with TF 1 compat statements
#from tensorflow.keras import backend as B 
from tensorflow.keras import models
from tensorflow.keras import layers
from tensorflow.keras import regularizers
from tensorflow.keras import optimizers
from tensorflow.keras.optimizers import schedules
from tensorflow.keras.utils import to_categorical
from tensorflow.keras.datasets import mnist

from tensorflow.python.client import device_lib

import matplotlib as mpl
from matplotlib import pyplot as plt
from matplotlib.colors import ListedColormap
import matplotlib.patches as mpat 

from IPython.core.tests.simpleerr import sysexit

class My_OIP:
    '''
    @summary: This class allows for the creation and the display of OIP-patterns, 
              to which a selected map of a CNN-model and related filters react maximally
    
    @version: Version 0.6, 10.10.2020
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    @change: Revised methods 
    @requires: In the present version the class My_OIP requires: 
                * a CNN-model which works with standardized (!) input images, size 28x28,
                * a CNN-Modell which was trained on MNIST digit data,
                * exactly 4 length scales for random data fluctations are used to compose initial statistial image data 
                  (the length scales should roughly have a factor of 2 between them) 
                * Assumption : exactly 1 input image and not a batch of images is assumed in various methods 
    
    @note: Main Functions:     
    0) _init__()
    1) _load_cnn_model()             => load cnn-model
    2) _build_oip_model()            => build an oip-model to create OIP-images
    3) _setup_gradient_tape_and_iterate_function()        
                                    => Implements TF2 GradientTape to watch input data for eager gradient calculation
                                    => Creates a convenience function by the help of Keras to iterate and optimize the OIP-adjustments
    4) _oip_strat_0_optimization_loop():
                                     => Method implementing a simple strategy to create OIP-images, 
                                        based on superposition of random data on long range data (compared to 28 px) 
                                        The optimization uses "gradient ascent"
 to get an optimum output of the selected Conv map 
    6) _derive_OIP():                => Method used to start the creation of an OIP-image for a chosen map 
                                        - based on an input image with statistical random date 
    6) _derive_OIP_for_Prec_Img():   => Method used to start the creation of an OIP-image for a chosen map 
                                       - based on an input image with was derived from a PRECURSOR run, 
                                       which tests the reaction of the map to large scale fluctuations 
                                        
    7) _build_initial_img_data():    => Builds an input image based on random data for fluctuations on 4 length scales 
    8) _build_initial_img_from_prec():    
                                     => Reconstruct an input image based on saved random data for long range fluctuations 
    9) _prepare_precursor():         => Prepare a _precursor run by setting up TF2 GradientTape and the _iterate()-function 
    10) _precursor():                => Precursor run which systematically tests the reaction of a selected convolutional map 
                                        to long range fluctuations based on a (3x3)-grid upscaled to the real image size  
    11) _display_precursor_imgs():   => A method which plots up to 8 selected precursor images with fluctuations,
                                        which triggered a maximum map reaction 
    12) _transfrom_tensor_to_img():  => A method which allows to transform tensor data of a standardized (!) image to standard image data 
                                        with (gray)pixel valus in [0, 255]. Parameters allow for a contrast enhancement. 
    
    Usage hints 
    ~~~~~~~~~~~
    @note: If maps of a new convolutional layer are to be investigated then method _build_oip_model(layer_name) has to be rerun 
           with the layer's name as input parameter
    '''
    
    # Method to initialize an instantiation object 
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    def __init__(self, cnn_model_file = 'cnn_MNIST_best.h5', 
                 layer_name = 'Conv2D_3', 
                 map_index = 0, 
                 img_dim = 28, 
                 b_build_oip_model = True  
                ): 
        '''
        @summary: Initialization of an object instance - read in a CNN model, build an OIP-Model 
        @note: Input: 
        ~~~~~~~~~~~~
        @param cnn_model_file:  Name of a file containing a fully trained CNN-model; 
                                the model can later be overwritten by self._load_cnn_model()
        @param layer_name:      We can define a layer name, which we are interested in,  already when starting;
                                the layer can later be overwritten by self._build_oip_model()
        @param map_index:       We can define a map, which we are interested in, already when starting;
                                A map-index is NOT required for building the OIP-model, but for the GradientTape-object 
        @param img_dim:         The dimension of the assumed quadratic images (2 for MNIST)

        @note: Major internal variables:
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @ivar _cnn_model:        A reference to the CNN model object
        @ivar _layer_name:       The name of convolutional layer 
                                 (can be overwritten by method _build_oip_model() ) 
        @ivar _map_index:        Index of the map in the chosen layer's output array 
                                 (can later be overwritten by other methods) 
        @ivar _r_cnn_inputs:     A reference to the input tensor of the CNN model 
                                 Could be a batch of images; but in this class only 1 image is assumed
        @ivar _layer_output:     Tensor with all maps of a certain layer    
        @
ivar _oip_submodel:     A new model connecting the input of the CNN-model with a certain map's (!) output
        @ivar _tape:             An instance of TF2's GradientTape-object 
                                    Watches input, output, loss of a model 
                                    and calculates gradients in TF2 eager mode 
        @ivar _r_oip_outputs:    Reference to the output of the new OIP-model = map-activation
        @ivar _r_oip_grads:      Reference to gradient tensors for the new OIP-model (output dependency on input image pixels)
        @ivar _r_oip_loss:       Reference to a loss defined on the OIP-output - i.e. on the activation values of the map's nodes;
                                 Normally chosen to be an average of the nodes' activations 
                                 The loss defines a hyperplane on the (28x28)-dim representation space of the input image pixel values  
        @ivar _val_oip_loss:     Loss value for a certain input image 
        @ivar _iterate           Reference toa Keras backend function which invokes the new OIP-model for a given image
                                 and calculates both loss and gradient values (in TF2 eager mode) 
                                 This is the function to be used in the optimization loop for OIPs
        
        @note: Internal Parameters controlling the optimization loop:
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @ivar _oip_strategy:        0, 1 - There are two strategies to evolve OIP patterns out of statistical data 
                                    - only the first strategy is supported in this version 
                                    Both strategies can be combined with a precursor calculation 
                                    0: Simple superposition of fluctuations at different length scales
                                    1: NOT YET SUPPORTED 
                                    Evolution over partially evolved images based on longer scale variations 
                                    enriched with fluctuations on shorter length scales 

        @ivar _ay_epochs:           A list of 4 optimization epochs to be used whilst 
                                    evolving the img data via strategy 1 and intermediate images 
        @ivar _n_epochs:            Number of optimization epochs to be used with strategy 0 
        @ivar _n_steps:             Defines at how many intermediate points we show images and report 
                                    during the optimization process 
        @ivar _epsilon:             Factor to control the amount of correction imposed by the gradient values of the oip-model 

        @note: Input image data of the OIP-model and references to it 
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @ivar _initial_precursor_img:  The initial image to start a precursor optimization with.
                                       Would normally be an image of only long range fluctuations. 
        @ivar _precursor_image:        The evolved image created and selected by the precursor loop 

        @ivar _initial_inp_img_data:  A tensor representing the data of the input image 
        @ivar _inp_img_data:          A tensor representig the 
        @ivar _img_dim:               We assume quadratic images to work with 
                                      with dimension _img_dim along each axis
                                      For the time being we only support MNIST images 
        
        @note: Internal parameters controlling the composition of random initial image data 
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @ivar _li_dim_steps:        A list of the intermediate dimensions for random data;
                                    these data are smoothly scaled to the image dimensions 
        @ivar _ay_facts:            A Numpy array of 4 factors to control the amount of 
                         
           contribution of the statistical variations 
                                    on the 4 length scales to the initial image
        
        @note: Internal variables to save data of a precursor run
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
        @ivar _list_of_covs: list of long range fluctuation data for a (3x3)-grid covering the image area 
        @ivar _li_fluct_enrichments: [li_facts, li_dim_steps] data for enrichment with small fluctuations 
        
        
        @note: Internal variables for plotting
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @ivar _li_axa: A Python list of references to external (Jupyter-) axes-frames for plotting 
        
        '''    
        
        # Input data and variable initializations
        # ****************************************
        
        # the model 
        # ~~~~~~~~~~
        self._cnn_model_file = cnn_model_file
        self._cnn_model      = None 
        
        # the chosen layer of the CNN-model
        self._layer_name = layer_name
        # the index of the map in the layer array
        self._map_index  = map_index
        
        # References to objects and the OIP-submodel
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        self._r_cnn_inputs  = None # reference to input of the CNN_model, also used in the oip-model  
        self._layer_output  = None
        self._oip_submodel  = None
        
        # References to watched GradientTape objects 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        self._tape          = None # TF2 GradientTape variable
        # some "references"
        self._r_oip_outputs = None # output of the oip-submodel to be watched 
        self._r_oip_grads   = None # gradients determined by GradientTape   
        self._r_oip_loss    = None # loss function
        # loss and gradient values (to be produced ba a backend function _iterate() )
        self._val_oip_grads = None
        self._val_oip_loss  = None
        
        # The Keras function to produce concrete outputs of the new OIP-model  
        self._iterate       = None
        
        # The strategy to produce an OIP pattern out of statistical input images 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~--------~~~~~~
        # 0: Simple superposition of fluctuations at different length scales 
        # 1: Move over 4 interediate images - partially optimized 
        self._oip_strategy = 0
        
        # Parameters controlling the OIP-optimization process 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~--------~~~~~~
        # number of epochs for optimization strategy 1
        self._ay_epochs    = np.array((20, 40, 80, 400), dtype=np.int32)
        len_epochs         = len(self._ay_epochs)
        
        # number of epochs for optimization strategy 0
        self._n_epochs     = self._ay_epochs[len_epochs-1]   
        self._n_steps      = 6   # divides the number of n_epochs into n_steps to produce intermediate outputs
        
        # size of corrections by gradients
        self._epsilon       = 0.01 # step-size for gradient correction
        
        # Input image-typess and references 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        # precursor image
        self._initial_precursor_img = None
        self._precursor_img         = None # output of the _precursor-method 
        
        # The input image for the OIP-creation - a superposition of inial random fluctuations
        self._initial_inp_img_data  = None  # The initial data constructed 
        self._inp_img_data          = None  # The data used and varied for optimization 
        # image dimension
        self._img_dim               = img_dim   # = 28 => MNIST images for the time being 
        
        # Parameters controlling the setup of an initial image 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~--------
~~~~~~~~~~~~~~~~~~~
        # The length scales for initial input fluctuations
        self._li_dim_steps = ( (3, 3), (7,7), (14,14), (28,28) ) # can later be overwritten 
        # Parameters for fluctuations  - used both in strategy 0 and strategy 1  
        self._ay_facts     = np.array( (0.5, 0.5, 0.5, 0.5), dtype=np.float32 )
        
        # Data of a _precursor()-run 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~
        self._list_of_covs = None       # list of long range fluctuation data for a (3x3)-grid covering the image area 
        self._li_fluct_enrichments = None # = [li_facts, li_dim_steps] list with with 2 list of data enrichment for small fluctuations 
        # These data are required to reconstruct the input image to which a map reacted 
        
        # List of references to axis subplots
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        # These references may change from Jupyter cell to Jupyter cell and provided by the called methods
        self._li_axa = None # will be set by methods according to axes-frames in Jupyter cells 
        # axis frames for a single image in 2 versions (with contrast enhancement)
        self._ax1_1 = None
        self._ax1_2 = None 
        
        
        # Variables for Deep Dream Analysis 
        # ***********************************
        #     Here we need a stack of tiled sub-images of a large image, as we subdivide on different length scales 
        self._num_tiles = 1
        self._t_image_stack = None 
        
        # ********************************************************
        # Model setup - load the cnn-model and build the OIP-model
        # ************
        if path.isfile(self._cnn_model_file): 
            # We trigger the initial load of a model 
            self._load_cnn_model(file_of_cnn_model = self._cnn_model_file, b_print_cnn_model = True)
            # We trigger the build of a new sub-model based on the CNN model used for OIP search 
            self._build_oip_model(layer_name = self._layer_name, b_print_oip_model = True ) 
        else:
            print("<\nWarning: The standard file " + self._cnn_model_file + 
                  " for the cnn-model could not be found!\n " + 
                  " Please use method _load_cnn_model() to load a valid model")
            sys.exit()
        return
    
    
    #
    # Method to load a specific CNN model
    # **********************************
    def _load_cnn_model(self, file_of_cnn_model=None, b_print_cnn_model=True ):
        '''
        @summary: Method to load a CNN-model from a h5-file and create a reference to its input (image)
        @version: 0.2 of 28.09.2020
        @requires: filename must already have been saved in _cnn_model_file or been given as a parameter 
        @requires: file must be a h5-file 
        @change: minor changes - documentation 
        @note: A reference to the CNN's input is saved internally
        @warning: An input in form of an image - a MNIST-image - is implicitly assumed
        
        @note: Parameters
        -----------------
        @param file_of_cnn_model: Name of h5-file with the trained (!) CNN-model
        @param b_print_cnn_model: boolean - Print some information on the CNN-model 
        '''
        if file_of_cnn_model != None:
            self._cnn_model_file = file_of_cnn_model
        
        # Check existence of the file
        if not path.isfile(self._cnn_model_file): 
            print("\nWarning: The file " + file_of_cnn_model + 
                  " for the cnn-model could not be found!\n" + 
                  "Please change the parameter \"file_of_cnn_model\"" + 
                  " to load a valid model")
        
        # load the CNN model 
        self._cnn_model = models.load_model(self._cnn_model_file)
        
        # Inform about the model and its 
file
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~
        print("Used file to load a ´ model = ", self._cnn_model_file)
        # we print out the models structure
        if b_print_cnn_model:
            print("Structure of the loaded CNN-model:\n")
            self._cnn_model.summary()
        
        # handle/references to the models input => more precise the input image 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        #    Note: As we only have one image instead of a batch 
        #    we pick only the first tensor element!
        #    The inputs will be needed for buildng the oip-model 
        self._r_cnn_inputs = self._cnn_model.inputs[0]  # !!! We have a btach with just ONE image 
        
        # print out the shape - it should be known from the original cnn-model
        if b_print_cnn_model:
            print("shape of cnn-model inputs = ", self._r_cnn_inputs.shape)
        
        return
    
    
    #
    # Method to construct a model to optimize input for OIP creation 
    # ***************************************
    def _build_oip_model(self, layer_name = 'Conv2D_3', b_print_oip_model=True ): 
        '''
        @summary: Method to build a new (sub-) model - the "OIP-model" - of the CNN-model by 
                  connectng the input of the CNN-model with one of its Conv-layers
        @version: 0.4 of 28.09.2020
        @change: Minor changes - documentation 
        @note: We need a Conv layer to build a working model for input image optimization
        We get the Conv layer by the layer's name 
        The new model connects the first input element of the CNN to the output maps of the named Conv layer CNN 
        We use Keras' models.Model() functionality 
        @note: The layer's name is crucial for all later investigations - if you want to change it this method has to be rerun 
        @requires: The original, trained CNN-model must be loaded and referenced by self._cnn_model 
        @warning: Only 1 input image and not a batch is implicitly assumed 
        
        @note: Parameters
        -----------------
        @param layer_name: Name of the convolutional layer of the CNN for whose maps we want to find OIP patterns
        @param b_print_oip_model: boolean - Print some information on the OIP-model 
        
        '''
        # free some RAM - hopefully 
        del self._oip_submodel
        
        # check for loaded CNN-model
        if self._cnn_model == None: 
            print("Error: CNN-model not yet defined.")
            sys.exit()
        
        # get layer name 
        self._layer_name = layer_name
        
        # We build a new model based on the model inputs and the output 
        self._layer_output = self._cnn_model.get_layer(self._layer_name).output
        # Note: We do not care at the moment about a complex composition of the input 
        # We trust in that we handle only one image - and not a batch
        
        # Create the sub-model via Keras' models.Model()
        model_name = "mod_oip__" + layer_name 
        self._oip_submodel = models.Model( [self._r_cnn_inputs], [self._layer_output], name = model_name)                                    

        # We print out the oip model structure
        if b_print_oip_model:
            print("Structure of the constructed OIP-sub-model:\n")
            self._oip_submodel.summary()
        return
    
    
    #
    # Method to set up GradientTape and an iteration function providing loss and gradient values  
    # *********************************************************************************************
    def _setup_gradient_tape_and_iterate_function(self, b_print = True, b_full_layer = False):
        '''
        @summary: Central method to watch input variables and resulting gradient changes 
        @version: 0.6 of 12.12.2020
n        @change: V0.6: We add the definition of a loss function for a whole layer 
        @note: For TF2 eager execution we need to watch input changes and trigger automatic gradient evaluation
        @note: The normalization of the gradient is strongly recommended; as we fix epsilon for correction steps 
               we thereby will get changes to the input data of an approximately constant order.
               This - together with standardization of the images (!) - will lead to convergence at the size of epsilon !
        @param b_full_layer: Boolean; define a loss function for a single map (map_index > -1) or the full layer (map_index = -1)
        '''   
        # Working with TF2 GradientTape
        self._tape = None

        # Watch out for input, output variables with respect to gradient changes
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        with tf.GradientTape() as self._tape: 
            # Input
            # ~~~~~
            self._tape.watch(self._r_cnn_inputs)
            # Output
            # ~~~~~~
            self._r_oip_outputs = self._oip_submodel(self._r_cnn_inputs)
            
            # only for testing
            # *******************
            #t_shape = self._r_oip_outputs[0, :, :, :].shape  # the 0 is important, else "Noen" => problems 
            #scaling_factor = tf.cast(tf.reduce_prod(t_shape), tf.float32) 
            #tf.print("scaling_factor: ", scaling_factor)
            #t_loss = tf.reduce_sum(tf.math.square(self._r_oip_outputs[0, :, :, :])) / scaling_factor
            
            # Define Loss 
            # ***********
            if (b_full_layer):
                # number of neurons over all layer maps 
                t_shape = self._r_oip_outputs[0, :, :, :].shape  # the 0 is important, else "Noen" => problems 
                scaling_factor = tf.cast(tf.reduce_prod(t_shape), tf.float32) # shape! eg. 3x3x128 for layer 3 
                tf.print("scaling_factor: ", scaling_factor)
                
                # The scaled total loss of the layer 
                self._r_oip_loss = tf.reduce_sum(tf.math.square(self._r_oip_outputs[0, :, :, :])) / scaling_factor
                
                # self._r_oip_loss = tf.reduce_mean(self._r_oip_outputs[0, :, :, self._map_index])
            else:
                self._r_oip_loss = tf.reduce_mean(self._r_oip_outputs[0, :, :, self._map_index])
            
            #self._loss = B.mean(oip_output[:, :, :, map_index])
            #self._loss = B.mean(oip_outputs[-1][:, :, map_index])
            #self._loss = tf.reduce_mean(oip_outputs[-1][ :, :, map_index])
            if b_print:
                print(self._r_oip_loss)
                print("shape of oip_loss = ", self._r_oip_loss.shape)
        
        # Gradient definition and normalization
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        self._r_oip_grads  = self._tape.gradient(self._r_oip_loss, self._r_cnn_inputs)
        print("shape of grads = ", self._r_oip_grads.shape)

        # normalization of the gradient - required for convergence 
        t_tiny = tf.constant(1.e-7, tf.float32)
        self._r_oip_grads /= (tf.sqrt(tf.reduce_mean(tf.square(self._r_oip_grads))) + t_tiny)
        #self._r_oip_grads /= (B.sqrt(B.mean(B.square(self._r_oip_grads))) + 1.e-7)
        #self._r_oip_grads = tf.image.per_image_standardization(self._r_oip_grads)

        # Define an abstract recallable Keras function as a convenience function for iterations 
        #     The _iterate()-function produces loss and gradient values for corrected img data 
        #     The first list of addresses points to the input data, the last to the output data 
        self._iterate = B.function( [self._r_cnn_inputs], [self._r_oip_loss, self._r_oip_grads] )
        
    
    #        
    # Method to optimize an emerging OIP out of statistical input 
image data 
    # (simple strategy - just optimize, no precursor, no intermediate pattern evolution, ..) 
    # ********************************
    def _oip_strat_0_optimization_loop(self, conv_criterion = 5.e-4, 
                                            b_stop_with_convergence = False,
                                            b_show_intermediate_images = True,
                                            b_print = True):
        '''
        @summary: Method to control the optimization loop for OIP reconstruction of an initial input image
                  with a statistical distribution of pixel values. 
        @version: 0.4 of 28.09.2020
        @changes: Minor changes - eliminated some unused variables
        @note:    The function also provides intermediate output in the form of printed data and images !.
        @requires: An input image tensor must already be available at _inp_img_data - created by _build_initial_img_data()
        @requires: Axis-objects for plotting, typically provided externally by the calling functions 
                  _derive_OIP() or _precursor()
        
        @note: Parameters:
        ----------------- 
        @param conv_criterion:  A small threshold number for (difference of loss-values / present loss value )
        @param b_stop_with_convergence: Booelan which decides whether we stop a loop if the conv-criterion is fulfilled
        @param b_show_intermediate_image: Boolean which decides whether we show up to 8 intermediate images 
        @param b_print: Boolean which decides whether we print intermediate loss values 
        
        @note: Intermediate information is provided at _n_steps intervals, 
               which are logarithmically distanced with respect to _n_epochs
               Reason: Most changes happen at the beginning 
        @note: This method produces some intermediate output during the optimization loop in form of images.
        It uses an external grid of plot frames and their axes-objects. The addresses of the 
        axis-objects must provided by an external list "li_axa[]" to self._li_axa[].  
        We need a seqence of _n_steps+2 axis-frames (or more) => length(_li_axa) >= _n_steps + 2). 
        
        @todo: Loop not optimized for TF 2 - but not so important here - a run takes less than a second 
        
        '''
        
        # Check that we already an input image tensor
        if ( (self._inp_img_data == None) or 
             (self._inp_img_data.shape[1] != self._img_dim) or 
             (self._inp_img_data.shape[2] != self._img_dim) ) :
            print("There is no initial input image or it does not fit dimension requirements (28,28)")
            sys.exit()

        # Print some information
        if b_print:
            print("*************\nStart of optimization loop\n*************")
            print("Strategy: Simple initial mixture of long and short range variations")
            print("Number of epochs = ", self._n_epochs)
            print("Epsilon =  ", self._epsilon)
            print("*************")

        # some initial value
        loss_old = 0.0
        
        # Preparation of intermediate reporting / img printing
        # --------------------------------------
        # Logarithmic spacing of steps (most things happen initially)
        n_el = math.floor(self._n_epochs / 2**(self._n_steps) ) 
        li_int = []
        if n_el != 0:
            for j in range(self._n_steps):
                li_int.append(n_el*2**j)
        else:  # linear spacing
            n_el = math.floor(self._n_epochs / (self._n_steps+1) ) 
            for j in range(self._n_steps+1):
                li_int.append(n_el*j)
        
        if b_print:
            print("li_int = ", li_int)
        
        # A counter for intermediate reporting  
        n_rep = 0
        
        # 
Convergence? - A list for steps meeting the convergence criterion
        # ~~~~~~~~~~~~
        li_conv = []
        
        
        # optimization loop 
        # *******************
        # counter for steps with zero loss and gradient values 
        n_zeros = 0
        
        for j in range(self._n_epochs):
            
            # Get output values of our Keras iteration function 
            # ~~~~~~~~~~~~~~~~~~~
            self._val_oip_loss, self._val_oip_grads = self._iterate([self._inp_img_data])
            
            # loss difference to last step - shuold steadily become smaller 
            loss_diff = self._val_oip_loss - loss_old 
            #if b_print:
            #    print("j: ", j, " :: loss_val = ", self._val_oip_loss, " :: loss_diff = ",  loss_diff)
            #    # print("loss_diff = ", loss_diff)
            loss_old = self._val_oip_loss
            
            if j > 10 and (loss_diff/(self._val_oip_loss + 1.-7)) < conv_criterion:
                li_conv.append(j)
                lenc = len(li_conv)
                # print("conv - step = ", j)
                # stop only after the criterion has been met in 4 successive steps
                if b_stop_with_convergence and lenc > 5 and li_conv[-4] == j-4:
                    return
            
            grads_val     = self._val_oip_grads
            #grads_val =   normalize_tensor(grads_val)
            
            # The gradients average value 
            avg_grads_val = (tf.reduce_mean(grads_val)).numpy()
            
            # Check if our map reacts at all
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            if self._val_oip_loss == 0.0 and avg_grads_val == 0.0 and b_print :
                print( "0-values, j= ", j, 
                       " loss = ", self._val_oip_loss, " avg_loss = ", avg_grads_val )
                n_zeros += 1
            
            if n_zeros > 10 and b_print: 
                print("More than 10 times zero values - Try a different initial random distribution of pixel values")
                return
            
            # gradient ascent => Correction of the input image data 
            # ~~~~~~~~~~~~~~~
            self._inp_img_data += self._val_oip_grads * self._epsilon
            
            # Standardize the corrected image - we won't get a convergence otherwise 
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            self._inp_img_data = tf.image.per_image_standardization(self._inp_img_data)
            
            # Some output at intermediate points 
            #     Note: We us logarithmic intervals because most changes 
            #           appear in the intial third of the loop's range  
            if (j == 0) or (j in li_int) or (j == self._n_epochs-1) :
                if b_print or (j == self._n_epochs-1):
                    # print some info 
                    print("\nstep " + str(j) + " finalized")
                    #print("Shape of grads = ", grads_val.shape)
                    print("present loss_val = ", self._val_oip_loss)
                    print("loss_diff = ", loss_diff)
                # show the intermediate image data 
                if b_show_intermediate_images: 
                    imgn = self._inp_img_data[0,:,:,0].numpy()
                    # print("Shape of intermediate img = ", imgn.shape)
                    self._li_axa[n_rep].imshow(imgn, cmap=plt.cm.get_cmap('viridis'))
                    # counter
                    n_rep += 1
        
        return
    
    
    #        
    # Standard UI-method to derive OIP from a given initial input image
    # ********************
    def _derive_OIP(self, map_index = 1, 
                          n_epochs = None, 
                          n_steps = 6, 
                          epsilon = 
0.01, 
                          conv_criterion = 5.e-4, 
                          li_axa = [], 
                          ax1_1 = None, ax1_2 = None, 
                          b_stop_with_convergence = False,
                          b_show_intermediate_images = True,
                          b_print = True,
                          centre_move = 0.33, fact = 1.0):
        '''
        @summary: Method to create an OIP-image for a given initial input image
                  This is the standard user interface for finding an OIP 
        @warning: This method should NOT be used for finding an initial precursor image 
                  Use _prepare_precursor() to define the map first and then _precursor() to evaluate initial images 
        @version: V0.5, 12.12.2020
        @change:  V0.4: Minor changes - added internal _li_axa for plotting, added documentation 
                  This method starts the process of producing an OIP of statistical input image data
        @change:  V0.5 : map_index can now have the value "-". Then a loss function for the whole layer (instead of a single map) is prepared
        @requires: A map index (or -1) should be provided to this method 
        @requires: An initial input image with statistical fluctuations of pixel values must have been created. 

        @warning:    This version only supports the most simple strategy - "strategy 0" 
        -------------    Optimize in one loop - starting from a superposition of fluctuations
                         No precursor, no intermediate evolutions

        @note: Parameters:
        -----------------
        @param map_index: We can and should chose a map here  (overwrites previous settings)
                          If map_index == -1 => We take a loss for the whole layer  
        @param n_epochs: Number of optimization steps  (overwrites previous settings) 
        @param n_steps:  Defines number of intervals (with length n_epochs/ n_steps) for reporting
                         standard value: 6 => 8 images - start image, end image + 6 intermediate 
                         This number also sets a requirement for providing (n_step + 2) external axis-frames 
                         to display intermediate images of the emerging OIP  
                         => see _oip_strat_0_optimization_loop()
        @param epsilon:  Size for corrections by gradient values
        @param conv_criterion: A small threshold number for convegenc (checks:  difference of loss-values / present loss value )
        @param b_stop_with_convergence: 
                         Booelan which decides whether we stop a loop if the conv-criterion is fulfilled
        @param _li_axa: A Python list of references to external (Jupyter-) axes-frames for plotting 
                 
        
        @note: Preparations for plotting: 
        We need n_step + 2 axis-frames which must be provided externally
        
        With Jupyter this can externally be done by statements like 

        # figure
        # -----------
        #sizing
        fig_size = plt.rcParams["figure.figsize"]
        fig_size[0] = 16
        fig_size[1] = 8
        fig_a = plt.figure()
        axa_1 = fig_a.add_subplot(241)
        axa_2 = fig_a.add_subplot(242)
        axa_3 = fig_a.add_subplot(243)
        axa_4 = fig_a.add_subplot(244)
        axa_5 = fig_a.add_subplot(245)
        axa_6 = fig_a.add_subplot(246)
        axa_7 = fig_a.add_subplot(247)
        axa_8 = fig_a.add_subplot(248)
        li_axa = [axa_1, axa_2, axa_3, axa_4, axa_5, axa_6, axa_7, axa_8]
        
        '''
        # Get input parameters
        self._map_index = map_index
        self._n_epochs  = n_epochs   
        self._n_steps   = n_steps
        self._epsilon   = epsilon
        
        # references to plot frames 
        self._li_axa = li_axa
        num_frames = len(li_
axa)
        if num_frames < n_steps+2:
            print("The number of available image frames (", num_frames, ") is smaller than required for intermediate output (", n_steps+2, ")")
            sys.exit()
        
        # 2 axes frames to display the final OIP image (with contrast enhancement) 
        self._ax1_1 = ax1_1
        self._ax1_2 = ax1_2
        
        # number of epochs for optimization strategy 0 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        if n_epochs == None:
            len_epochs = len(self._ay_epochs)
            self._n_epochs   = self._ay_epochs[len_epochs-1]
        else: 
            self._n_epochs = n_epochs

        # Reset some variables  
        self._val_oip_grads = None
        self._val_oip_loss  = None 
        self._iterate       = None 

        # Setup the TF2 GradientTape watch and a Keras function for iterations 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        # V0.5 => map_index == "-1"
        if self._map_index == -1: 
            self._setup_gradient_tape_and_iterate_function(b_print = b_print, b_full_layer=True)
            if b_print:
                print("GradientTape watch activated (map-based: map = ", self._map_index, ")")
        else: 
            self._setup_gradient_tape_and_iterate_function(b_print = b_print, b_full_layer=False)
            if b_print:
                print("GradientTape watch activated (layer-based: layer = ", self._layer_name, ")")
        
        '''
        # Gradient handling - so far we only deal with addresses 
        # ~~~~~~~~~~~~~~~~~~
        self._r_oip_grads  = self._tape.gradient(self._r_oip_loss, self._r_cnn_inputs)
        print("shape of grads = ", self._r_oip_grads.shape)
        
        # normalization of the gradient 
        self._r_oip_grads /= (B.sqrt(B.mean(B.square(self._r_oip_grads))) + 1.e-7)
        #self._r_oip_grads = tf.image.per_image_standardization(self._r_oip_grads)
        
        # define an abstract recallable Keras function 
        # producing loss and gradients for corrected img data 
        # the first list of addresses points to the input data, the last to the output data 
        self._iterate = B.function( [self._r_cnn_inputs], [self._r_oip_loss, self._r_oip_grads] )
        '''
            
        # get the initial image into a variable for optimization 
        self._inp_img_data = self._initial_inp_img_data

        # Start optimization loop for strategy 0 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        if self._oip_strategy == 0: 
            self._oip_strat_0_optimization_loop( conv_criterion = conv_criterion, 
                                                b_stop_with_convergence = b_stop_with_convergence,  
                                                b_show_intermediate_images = b_show_intermediate_images,
                                                b_print = b_print
                                               )
        
        # Display the last OIP-image created at the end of the optimization loop
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        # standardized image 
        oip_img = self._inp_img_data[0,:,:,0].numpy()
        # transformed image 
        oip_img_t = self._transform_tensor_to_img(T_img=self._inp_img_data[0,:,:,0], 
                                                  centre_move = centre_move,
                                                  fact = fact)
        
        # display 
        ax1_1.imshow(oip_img, cmap=plt.cm.get_cmap('viridis'))
        ax1_2.imshow(oip_img_t, cmap=plt.cm.get_cmap('viridis'))
        
        return
    
    
    # 
    # Method to derive OIP from a given initial input image if map_index is already defined 
    # ********************
    def _derive_OIP_for_Prec_
Img(self, 
                          n_epochs = None, 
                          n_steps = 6, 
                          epsilon = 0.01, 
                          conv_criterion = 5.e-4, 
                          li_axa = [], 
                          ax1_1 = None, ax1_2 = None, 
                          b_stop_with_convergence = False,
                          b_show_intermediate_images = True,
                          b_print = True):
        '''
        @summary: Method to create an OIP-image for an already given map-index and a given initial input image
                  This is the core of OIP-detection, which starts the optimization loop  
        @warning: This method should NOT be used directly for finding an initial precursor image 
                  Use _prepare_precursor() to define the map first and then _precursor() to evaluate initial images 
        @version: V0.4, 28.09.2020
        @changes: Minor changes - added internal _li_axa for plotting, added documentation 
                  This method starts the process of producing an OIP of statistical input image data
        
        @note:    This method should only be called after _prepare_precursor(), _precursor(), _build_initial_img_prec() 
                  For a trial of different possible precursor images rerun _build_initial_img_prec() with a different index
        
        @requires: A map index should be provided to this method 
        @requires: An initial input image with statistical fluctuations of pixel values must have been created. 

        @warning:    This version only supports the most simple strategy - "strategy 0" 
        -------------    Optimize in one loop - starting from a superposition of fluctuations
                         no intermediate evolutions

        @note: Parameters:
        -----------------
        @param n_epochs: Number of optimization steps  (overwrites previous settings) 
        @param n_steps:  Defines number of intervals (with length n_epochs/ n_steps) for reporting
                         standard value: 6 => 8 images - start image, end image + 6 intermediate 
                         This number also sets a requirement for providing (n_step + 2) external axis-frames 
                         to display intermediate images of the emerging OIP  
                         => see _oip_strat_0_optimization_loop()
        @param epsilon:  Size for corrections by gradient values
        @param conv_criterion: A small threshold number for convegenc (checks:  difference of loss-values / present loss value )
        @param b_stop_with_convergence: 
                         Booelan which decides whether we stop a loop if the conv-criterion is fulfilled
        @param _li_axa: A Python list of references to external (Jupyter-) axes-frames for plotting 
                 
        
        @note: Preparations for plotting: 
        We need n_step + 2 axis-frames which must be provided externally
        
        With Jupyter this can externally be done by statements like 

        # figure
        # -----------
        #sizing
        fig_size = plt.rcParams["figure.figsize"]
        fig_size[0] = 16
        fig_size[1] = 8
        fig_a = plt.figure()
        axa_1 = fig_a.add_subplot(241)
        axa_2 = fig_a.add_subplot(242)
        axa_3 = fig_a.add_subplot(243)
        axa_4 = fig_a.add_subplot(244)
        axa_5 = fig_a.add_subplot(245)
        axa_6 = fig_a.add_subplot(246)
        axa_7 = fig_a.add_subplot(247)
        axa_8 = fig_a.add_subplot(248)
        li_axa = [axa_1, axa_2, axa_3, axa_4, axa_5, axa_6, axa_7, axa_8]
        
        '''
        # Get input parameters
        self._n_epochs  = n_epochs   
        self._n_steps   = n_steps
        self._epsilon   = epsilon
        
        # references to plot frames 
        self._li_axa = li_axa
        num_frames 
= len(li_axa)
        if num_frames < n_steps+2:
            print("The number of available image frames (", num_frames, ") is smaller than required for intermediate output (", n_steps+2, ")")
            sys.exit()
            
        # 2 axes frames to display the final OIP image (with contrast enhancement) 
        self._ax1_1 = ax1_1
        self._ax1_2 = ax1_2
        
        # number of epochs for optimization strategy 0 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        if n_epochs == None:
            len_epochs = len(self._ay_epochs)
            self._n_epochs   = self._ay_epochs[len_epochs-1]
        else: 
            self._n_epochs = n_epochs
        
        # Note: No setup of GradientTape and _iterate(required) - this is done by _prepare_precursor 
            
        # get the initial image into a variable for optimization 
        self._inp_img_data = self._initial_inp_img_data

        # Start optimization loop for strategy 0 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        if self._oip_strategy == 0: 
            self._oip_strat_0_optimization_loop( conv_criterion = conv_criterion, 
                                                b_stop_with_convergence = b_stop_with_convergence,  
                                                b_show_intermediate_images = b_show_intermediate_images,
                                                b_print = b_print
                                               )
        # Display the last OIP-image created at the end of the optimization loop
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        # standardized image 
        oip_img = self._inp_img_data[0,:,:,0].numpy()
        # transfored image 
        oip_img_t = self._transform_tensor_to_img(T_img=self._inp_img_data[0,:,:,0])
        
        # display 
        ax1_1.imshow(oip_img, cmap=plt.cm.get_cmap('viridis'))
        ax1_2.imshow(oip_img_t, cmap=plt.cm.get_cmap('viridis'))
        
        return
    
    
    # 
    # Method to build an initial image from a superposition of random data on different length scales 
    # ***********************************
    def _build_initial_img_data( self, 
                                 strategy = 0, 
                                 li_epochs    = [20, 50, 100, 400], 
                                 li_facts     = [0.5, 0.5, 0.5, 0.5],
                                 li_dim_steps = [ (3,3), (7,7), (14,14), (28,28) ], 
                                 b_smoothing = False,
                                 ax1_1 = None, ax1_2 = None):
        
        '''
        @summary: Standard method to build an initial image with random fluctuations on 4 length scales
        @version: V0.2 of 29.09.2020
        
        @note: This method should NOT be used for initial images based on a precursor images. 
               See _build_initial_img_prec(), instead.  
        
        @note: This method constructs an initial input image with a statistical distribution of pixel-values.
        We use 4 length scales to mix fluctuations with different "wave-length" by a simple approach: 
        We fill four square with a different numer of cells below the number of pixels 
        in each dimension of the real input image; e.g. (4x4), (7x7, (14x14), (28,28) <= (28,28). 
        We fill the cells with random numbers in [-1.0, 1.]. We smootly scale the resulting pattern 
        up to (28,28) (or what ever the input image dimensions are) by bicubic interpolations 
        and eventually add up all values. As a final step we standardize the pixel value distribution.          
        
        @warning: This version works with 4 length scales, only. 
        @warning: In the present version th eparameters "strategy " and li_epochs have no effect 
        
        @note: Parameters:
        -----------------
r
        @param strategy:  The strategy, how to build an image (overwrites previous settings) - presently only 0 is supported 
        @param li_epochs: A list of epoch numbers which will be used in strategy 1 - not yet supported 
        @param li_facts:  A list of factors which the control the relative strength of the 4 fluctuation patterns 
        @param li_dim_steps: A list of square dimensions for setting the length scale of the fluctuations  
        @param b_smoothing: Parameter which builds a control image   
        @param ax1_1: matplotlib axis-frame to display the built image 
        @param ax1_2: matplotlib axis-frame to display a second version of the built image 
        
        '''
        
        # Get input parameters 
        # ~~~~~~~~~~~~~~~~~~
        self._oip_strategy = strategy               # no effect in this version 
        self._ay_epochs    = np.array(li_epochs)    # no effect in this version 
        
        # factors by which to mix the random number fluctuations of the different length scales 
        self._ay_facts     = np.array(li_facts)
        # dimensions of the squares which simulate fluctuations 
        self._li_dim_steps = li_dim_steps
        
        # A Numpy array for the eventual superposition of random data 
        fluct_data = None
        
        
        # Strategy 0: Simple superposition of random patterns at 4 different wave-length
        # ~~~~~~~~~~
        if self._oip_strategy == 0:
            
            dim_1_1 = self._li_dim_steps[0][0] 
            dim_1_2 = self._li_dim_steps[0][1] 
            dim_2_1 = self._li_dim_steps[1][0] 
            dim_2_2 = self._li_dim_steps[1][1] 
            dim_3_1 = self._li_dim_steps[2][0] 
            dim_3_2 = self._li_dim_steps[2][1] 
            dim_4_1 = self._li_dim_steps[3][0] 
            dim_4_2 = self._li_dim_steps[3][1] 
            
            fact1 = self._ay_facts[0]
            fact2 = self._ay_facts[1]
            fact3 = self._ay_facts[2]
            fact4 = self._ay_facts[3]
            
            # print some parameter information
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            print("\nInitial image composition - strategy 0:\n Superposition of 4 different wavelength patterns")
            print("Parameters:\n", 
                 fact1, " => (" + str(dim_1_1) +", " + str(dim_1_2) + ") :: ", 
                 fact2, " => (" + str(dim_2_1) +", " + str(dim_2_2) + ") :: ", 
                 fact3, " => (" + str(dim_3_1) +", " + str(dim_3_2) + ") :: ", 
                 fact4, " => (" + str(dim_4_1) +", " + str(dim_4_2) + ")" 
                 )
            
            # fluctuations
            fluct1 =  2.0 * ( np.random.random((1, dim_1_1, dim_1_2, 1)) - 0.5 ) 
            fluct2 =  2.0 * ( np.random.random((1, dim_2_1, dim_2_2, 1)) - 0.5 ) 
            fluct3 =  2.0 * ( np.random.random((1, dim_3_1, dim_3_2, 1)) - 0.5 ) 
            fluct4 =  2.0 * ( np.random.random((1, dim_4_1, dim_4_2, 1)) - 0.5 ) 
            
            # Scaling with bicubic interpolation to the required image size
            fluct1_scale = tf.image.resize(fluct1, [28,28], method="bicubic", antialias=True)
            fluct2_scale = tf.image.resize(fluct2, [28,28], method="bicubic", antialias=True)
            fluct3_scale = tf.image.resize(fluct3, [28,28], method="bicubic", antialias=True)
            fluct4_scale = fluct4
            
            # superposition
            fluct_data = fact1*fluct1_scale + fact2*fluct2_scale + fact3*fluct3_scale + fact4*fluct4_scale
            
        
        # get the standardized plus smoothed and unsmoothed image 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        #  TF2 provides a function performing standardization of image data function
        fluct_data_unsmoothed = tf.image.per_image_
standardization(fluct_data) 
        fluct_data_smoothed   = tf.image.per_image_standardization(
                                    tf.image.resize( fluct_data, [28,28], method="bicubic", antialias=True) )
        
        if b_smoothing: 
            self._initial_inp_img_data = fluct_data_smoothed
        else:
            self._initial_inp_img_data = fluct_data_unsmoothed
        
        # Display of both variants => there should be no difference 
        # ~~~~~~~~~~~~~~~~~~~~~~~~
        img_init_unsmoothed = fluct_data_unsmoothed[0,:,:,0].numpy()
        img_init_smoothed   = fluct_data_smoothed[0,:,:,0].numpy()
        ax1_1.imshow(img_init_unsmoothed, cmap=plt.cm.get_cmap('viridis'))
        ax1_2.imshow(img_init_smoothed, cmap=plt.cm.get_cmap('viridis'))
        
        print("Initial images plotted")
        
        return self._initial_inp_img_data    


    # 
    # Method to build an initial image from a superposition of a PRECURSOR image with random data on different length scales 
    # ***********************************
    def _build_initial_img_from_prec( self, 
                                 prec_index = -1,
                                 strategy = 0, 
                                 li_epochs    = (20, 50, 100, 400), 
                                 li_facts     = (1.0, 0.0, 0.0, 0.0, 0.0),
                                 li_dim_steps = ( (3,3), (7,7), (14,14), (28,28) ), 
                                 b_smoothing = False,
                                 b_print = True, 
                                 b_display = False, 
                                 ax1_1 = None, ax1_2 = None):
        
        '''
        @summary: Method to build an initial image based on a Precursor image => Input for _derive_OIP_for_Prec_Img()
        @version: V0.3, 03.10.2020
        @changes: V0.2: Minor- only documentation and comparison of index to length of _li_of_flucts[] 
        @changes: V0.3: Added Booleans to control the output and display of images 
        @changes: V0.4: Extended the reconstruction part / extended documentation
        
        @note: This method differs from _build_initial_img_data() as follows:
                * It uses a Precursor image as the fundamental image 
                * The data of the Precursor Image will be reconstructed from a (3x3) fluctuation pattern and enrichments
                * This method adds even further fluctuations if requested 
        @note: This method should be called manually from a Jupyter cell 
        @note: This method saves the reconstructed input image into self._initial_inp_img_data
        @note: This method should be followed by a call of self._derive_OIP_for_Prec_Img()
        
        @requires: Large scale fluctuation data saved in self._li_of_flucts[]
        @requires: Additional enrichment information in self._li_of_fluct_enrichments[]
        
        @param prec_index: This is an index ([0, 7[) of a large scale fluctuation pattern which was saved in self._li_of_flucts[] 
                           during the run of the method "_precursor()". The image tensor is reconstructed from the fluctuation pattern. 
        @warning: We support a maximum of 8 selected fluctuation patterns for which a map reacts 
        @warning: However, less precursor patterns may be found - so you should watch for the output of _precursor() before you run this method
        
        @param li_facts:  A list of factors which the control the relative strength of the precursor image vs. 
                          4 additional fluctuation patterns 
        @warning: Normally, it makes no sense to set li_facts[1] > 0 - because this will destroy the original large scale pattern 
        
        @note: For other input parameters see _build_initial_img_data()
        '''
        
        # Get input parameters 
        self._oip_strategy 
= strategy
        self._ay_facts     = np.array(li_facts)
        self._ay_epochs    = np.array(li_epochs)
        self._li_dim_steps = li_dim_steps
        
        fluct_data = None
        
        # Reconstruct an precursor image from a saved large scale fluctuation pattern (result of _precursor() ) 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        length_li_cov = len(self._li_of_flucts)
        if prec_index > -1: 
            if length_li_cov < prec_index+1:
                print("index too large for number of detected patterns (", length_li_cov, ")")
                sys.exit()
            cov_p = self._li_of_flucts[prec_index][1][1]
            
            fluct0_scale_p = tf.image.resize(cov_p, [28,28], method="bicubic", antialias=True)
            
            # Add fluctuation enrichments - if saved [ len(self._li_fluct_enrichments) > 0 ]
            if len(self._li_fluct_enrichments) > 0:
                # Scaling enrichment flucts with bicubic interpolation to the required image size
                fluct1_p = self._li_fluct_enrichments[2][0] 
                fluct2_p = self._li_fluct_enrichments[2][1] 
                fluct3_p = self._li_fluct_enrichments[2][2] 
                fluct4_p = self._li_fluct_enrichments[2][3] 
                
                fact0_p = self._li_fluct_enrichments[0][0]
                fact1_p = self._li_fluct_enrichments[0][1]
                fact2_p = self._li_fluct_enrichments[0][2]
                fact3_p = self._li_fluct_enrichments[0][3]
                fact4_p = self._li_fluct_enrichments[0][4]
                
                fluct1_scale_p = tf.image.resize(fluct1_p, [28,28], method="bicubic", antialias=True)
                fluct2_scale_p = tf.image.resize(fluct2_p, [28,28], method="bicubic", antialias=True)
                fluct3_scale_p = tf.image.resize(fluct3_p, [28,28], method="bicubic", antialias=True)
                fluct4_scale_p = fluct4_p
                
                fluct_scale_p = fact0_p*fluct0_scale_p \
                 + fact1_p*fluct1_scale_p + fact2_p*fluct2_scale_p \
                 + fact3_p*fluct3_scale_p + fact4_p*fluct4_scale_p
                 
            else: 
                fluct_scale_p = fluct0_scale_p
            
            # get the img-data 
            fluct_data_p  = tf.image.per_image_standardization(fluct_scale_p)     
            fluct_data_p  = tf.where(fluct_data_p > 5.e-6, fluct_data_p, tf.zeros_like(fluct_data_p))
            self._initial_inp_img_data = fluct_data_p
            self._inp_img_data         = fluct_data_p
            
        
        # Strategy 0: Simple superposition of the precursor image AND additional patterns at 4 different wave-length
        # ~~~~~~~~~~
        if self._oip_strategy == 0:
            
            dim_1_1 = self._li_dim_steps[0][0] 
            dim_1_2 = self._li_dim_steps[0][1] 
            dim_2_1 = self._li_dim_steps[1][0] 
            dim_2_2 = self._li_dim_steps[1][1] 
            dim_3_1 = self._li_dim_steps[2][0] 
            dim_3_2 = self._li_dim_steps[2][1] 
            dim_4_1 = self._li_dim_steps[3][0] 
            dim_4_2 = self._li_dim_steps[3][1] 
            
            fact0 = self._ay_facts[0]
            fact1 = self._ay_facts[1]
            fact2 = self._ay_facts[2]
            fact3 = self._ay_facts[3]
            fact4 = self._ay_facts[4]
            
            # print some parameter information
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            if b_print:
                print("\nInitial image composition - strategy 0:\n Superposition of 4 different wavelength patterns")
                print("Parameters:\n", 
                     fact0, " => precursor image \n", 
                     fact1, " => (" + str(dim_1_1) +", " + str(dim_1_2) + ") :: ", 
                  
   fact2, " => (" + str(dim_2_1) +", " + str(dim_2_2) + ") :: ", 
                     fact3, " => (" + str(dim_3_1) +", " + str(dim_3_2) + ") :: ", 
                     fact4, " => (" + str(dim_4_1) +", " + str(dim_4_2) + ")" 
                     )
            
            # fluctuations
            fluct1 =  2.0 * ( np.random.random((1, dim_1_1, dim_1_2, 1)) - 0.5 ) 
            fluct2 =  2.0 * ( np.random.random((1, dim_2_1, dim_2_2, 1)) - 0.5 ) 
            fluct3 =  2.0 * ( np.random.random((1, dim_3_1, dim_3_2, 1)) - 0.5 ) 
            fluct4 =  2.0 * ( np.random.random((1, dim_4_1, dim_4_2, 1)) - 0.5 ) 
            
            # Scaling with bicubic interpolation to the required image size
            fluct1_scale = tf.image.resize(fluct1, [28,28], method="bicubic", antialias=True)
            fluct2_scale = tf.image.resize(fluct2, [28,28], method="bicubic", antialias=True)
            fluct3_scale = tf.image.resize(fluct3, [28,28], method="bicubic", antialias=True)
            fluct4_scale = fluct4
            
            # superposition with the already calculated image 
            fluct_data = fact0 * self._initial_inp_img_data  \
                         + fact1*fluct1_scale + fact2*fluct2_scale \
                         + fact3*fluct3_scale + fact4*fluct4_scale
            
        
        # get the standardized plus smoothed and unsmoothed image 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        #    TF2 provides a function performing standardization of image data function
        fluct_data_unsmoothed = fluct_data 
        fluct_data_smoothed   = tf.image.per_image_standardization(
                                    tf.image.resize( fluct_data, [28,28], 
                                                     method="bicubic", antialias=True) )
        
        if b_smoothing: 
            self._initial_inp_img_data = fluct_data_smoothed
        else:
            self._initial_inp_img_data = fluct_data_unsmoothed
        
        # There should be no difference 
        img_init_unsmoothed = fluct_data_unsmoothed[0,:,:,0].numpy()
        img_init_smoothed   = fluct_data_smoothed[0,:,:,0].numpy()
        
        if b_display:
            ax1_1.imshow(img_init_unsmoothed, cmap=plt.cm.get_cmap('viridis'))
            ax1_2.imshow(img_init_smoothed, cmap=plt.cm.get_cmap('viridis'))
            print("Initial images plotted")
        
        return self._initial_inp_img_data    
    
    #
    # Method to prepare a Precursor run which checks a variety of large scale fluctuations for optimum actvation  
    # ***********************************
    def _prepare_precursor(self, map_index = 120, b_print = False):
        '''
        @summary: A method to prepare a Precursor run by setting up GradientTape and the _ierate() function for an optimization loop
        @version: 0.2, 30.09.2020
        @changes: Minor - adaption to _setup_gradient_tape_and_iterate_function() instead of the obsolete _setup_gradient_tape()
        @requires: A loaded CNN-Model and an already built OIP-model 
        @requires: A valid map-index as input parameter 
        
        @note: This method sets up the GradientTape and _iterate only once 
               - it will not be done again during the investigation of thousands of different input images (with large scale fluctuations) 
               which we investigate during the _precursor()-run. 
        
        @param map_index: Index selecting a map for the CNN layer defined previously by _build_oip_model()
        @param b_print: Boolean - decides about intemediate output 
        
        '''
        
        # Get input parameters 
        # ~~~~~~~~~~~~~~~~~~~~~~
        self._map_index = map_index
        # Rest some variables  
        self._val_oip_grads = None
        self._val_oip_loss  = None 
 
       self._iterate       = None 
        
        # Setup the TF2 GradientTape watch
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        self._setup_gradient_tape_and_iterate_function(b_print = b_print)
        if b_print:
            print("GradientTape watch activated and _iterate()-function defined")
    
    
    # Method to prepare a Precursor run which checks a variety of large scale fluctuations for optimum actvation
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    def _precursor(self, 
                   li_pre_val=[0.2, 0.5, 0.8], 
                   num_epochs=10, 
                   loss_limit = 0.5, 
                   b_print = True, 
                   b_with_enriched_fluct = False, 
                   li_facts     = (1.0, 0.0, 0.0, 0.0, 0.1),
                   li_dim_steps = ( (3,3), (7,7), (14,14), (28,28) ), 
                   b_check = True, 
                   fig_a = None, 
                   li_axa = None,
                   # the next parameters are new in V0.6
                   b_show_test_input_images = False,
                   fig_test_img = None,
                   ax_b = None, 
                   interval_test_img = 1):

        '''
        @summary: Method to investigate thousands of input images with large scale fluctuations for the reaction of a specified map (filters)
                  and a given number of epochs in pattern creation
        @version: 0.6, 12.12.2020
        @changes: V0.5: Minor - documentation, skipped some superfluous statements 
        @changes: V0.6: Added intermediate plot output of constructed input images (a fig_a-reference must have been provided!) 
        @note: We select the 8 most dominant images - or less, if there are fewer input images which trigger the map 
        @requires: Previous run of _prepare_cursor() with a definition of the map-index
        @note: We vary only 3 given pixel values on (3x3) grids (19683 possibilities)
        @note: The optimization loop is completely done within this method - due to performance reasons
        
        @param li_pre_val: A list of three scaled pixel values between ]0, 1[ which shall be combined in (3x3)-fluctuation patterns
        
        @param num_epochs: The number of epochs used in the optimization loop for pattern creation
        @note: It is worthwile to experiment with the number of epochs - the (3x3)-pattern selection may change !!!
        
        @param loss_limit: Threshold of loss for which we register a fluctuation image as relevant 
        
        @param b_print: Boolean - controls printout for intermediate results - useful to see map response 
        @param b_check: Check the response of map for the first saved pattern - check the image reconstruction at the same time
        
        @note: Parameters to enrich the (3x3)-large scale fluctuation with a small scale pattern 
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @param b_with_enriched_fluct: Boolean - controls whether we enrich the long-range pattern with other additional patterns 
        @param li_facts:  A list of factors which the control the relative strength of the precursor image vs. 
                          4 additional fluctuation patterns 
        @param li_dim_steps: A list of square dimensions for setting the length scale of the fluctuations  
        
        @note: Parameters for plotting  
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @param fig_a: reference to the 8 axes-frame 
        @param li_axa: A Python list of references to external (Jupyter-) axes-frames for plotting 
        
        Plots for intermediate test images 
        Note that for inernediate image plotting the cell must have a command line with metacommand 
        %matplotlib notebook
        plt.ion()
        @param b_show_test_input_images = Boolean; show intermediate 
fluctuation patterns 
        @param fig_test_img: reference to external image plot frame. 
        @param ax_b: Rference to axis-frame for the intermediate display of test-images  
        
        @note: Preparations for plotting: 
        ---------------------------------
        fig_b : a simple figure for an image
        fig_a: We need 8 axis-frames which must be provided externally
        With Jupyter this can externally be done by statements like 

        # figure
        # -----------
        fig_b_pre, ax_b_pre = plt.subplots(1, figsize=(3,3))
        fig_b_pre.canvas.draw()
        
        fig_a_pre = plt.figure(2, figsize=(10,5))
        axa_1 = fig_a_pre.add_subplot(241)
        axa_2 = fig_a_pre.add_subplot(242)
        axa_3 = fig_a_pre.add_subplot(243)
        axa_4 = fig_a_pre.add_subplot(244)
        axa_5 = fig_a_pre.add_subplot(245)
        axa_6 = fig_a_pre.add_subplot(246)
        axa_7 = fig_a_pre.add_subplot(247)
        axa_8 = fig_a_pre.add_subplot(248)
        li_axa = [axa_1, axa_2, axa_3, axa_4, aab_5, axa_6, axa_7, axa_8]
        fig_a_pre.canvas.draw()
        
        
        '''
        # Internal parameter for number of selected input patterns 
        num_selected = 8 
        # check if length of li_axa is sufficient
        if li_axa == None or len(li_axa) < num_selected:
            print("Error: The length of the provided list with axes-frames for plotting must be at least ", num_selected )
            sys.exit()
        
        # get required exernal params 
        # ~~~~~~~~~~~~~~~~~~~~~~~~
        self._n_steps   = 2           # only a dummy 
        self._epsilon   = 0.01        # only a dummy  
        
        # number of epochs for optimization strategy 0 
        if num_epochs == None:
            len_epochs = len(self._ay_epochs)
            self._n_epochs   = self._ay_epochs[len_epochs-1]
        else: 
            self._n_epochs = num_epochs  
        
        # Create a fixed random flutution pattern which we later can overlay to the long range fluctuation patterns 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        self._li_dim_steps = li_dim_steps # dimensions for fluctuations 
        self._ay_facts     = np.array(li_facts)
        
        dim_1_1 = self._li_dim_steps[0][0] 
        dim_1_2 = self._li_dim_steps[0][1] 
        dim_2_1 = self._li_dim_steps[1][0] 
        dim_2_2 = self._li_dim_steps[1][1] 
        dim_3_1 = self._li_dim_steps[2][0] 
        dim_3_2 = self._li_dim_steps[2][1] 
        dim_4_1 = self._li_dim_steps[3][0] 
        dim_4_2 = self._li_dim_steps[3][1] 
        
        fact0 = self._ay_facts[0]
        fact1 = self._ay_facts[1]
        fact2 = self._ay_facts[2]
        fact3 = self._ay_facts[3]
        fact4 = self._ay_facts[4]
        
        # Create fluctuation patterns for enrichment 
        fluct1 =  2.0 * ( np.random.random((1, dim_1_1, dim_1_2, 1)) - 0.5 ) 
        fluct2 =  2.0 * ( np.random.random((1, dim_2_1, dim_2_2, 1)) - 0.5 ) 
        fluct3 =  2.0 * ( np.random.random((1, dim_3_1, dim_3_2, 1)) - 0.5 ) 
        fluct4 =  2.0 * ( np.random.random((1, dim_4_1, dim_4_2, 1)) - 0.5 ) 
        
        li_fluct = [fluct1, fluct2, fluct3, fluct4]
        
        # Scaling with bicubic interpolation to the required image size
        fluct1_scale = tf.image.resize(fluct1, [28,28], method="bicubic", antialias=True)
        fluct2_scale = tf.image.resize(fluct2, [28,28], method="bicubic", antialias=True)
        fluct3_scale = tf.image.resize(fluct3, [28,28], method="bicubic", antialias=True)
        fluct4_scale = fluct4

        
        # Create cartesian product of combinatoric possibilities for a (3x3)-grid of long range fluctuations
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        cp = list(product(li_pre_val, repeat=9))
      
  num = len(cp) 
        print ("We test ", num, " possibilities for a (3x3) fluctuations ")
        
        # Prepare lists to save parameter data for the fluctuation pattern 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        # Intermediate list to save relevant long scale fluctuations 
        d_cov = {}
        # list to save parameters for an enrichments of the large scale pattern with small fluctuations
        if b_with_enriched_fluct:
            self._li_fluct_enrichments = [li_facts, li_dim_steps, li_fluct]
        else:
            self._li_fluct_enrichments = []
            
        # Loop to check for relevant fluctuations => Loop over all combinations
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        for i_cp in range(num): 
            
            # create the value distribution 
            cov = np.array(cp[i_cp])
            cov = cov.reshape(1,3,3,1) 

            # create basic image to investigate
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            fluct_scale = tf.image.resize(cov, [28,28], method="bicubic", antialias=True) 
            
            # enrich with additional smallscale fluctuations 
            if b_with_enriched_fluct: 
                # superposition with the already calculated image 
                fluct_scale = fact0 * fluct_scale \
                             + fact1*fluct1_scale + fact2*fluct2_scale \
                             + fact3*fluct3_scale + fact4*fluct4_scale
            
            #standardization of the image data 
            fluct_data  = tf.image.per_image_standardization(fluct_scale)     
            # eliminatng very small values - prove to be helpful in many cases 
            fluct_data = tf.where(fluct_data > 5.e-6, fluct_data, tf.zeros_like(fluct_data))
            
            # save image data 
            self._initial_inp_img_data = fluct_data
            self._inp_img_data         = fluct_data
            
            # Display the present input image 
            if b_show_test_input_images and i_cp%interval_test_img == 0: 
                img_b = fluct_data[0, :,:, 0].numpy()
                ax_b.imshow(img_b, cmap=plt.cm.get_cmap('viridis'))
                fig_test_img.canvas.draw()
            
            # optimization loop 
            # ~~~~~~~~~~~~~~~~~
            for j in range(self._n_epochs):
                # Get output values of our Keras iteration function 
                self._val_oip_loss, self._val_oip_grads = self._iterate([self._inp_img_data])
                # gradient ascent => Correction of the input image data 
                self._inp_img_data += self._val_oip_grads * self._epsilon
                # Standardize the corrected image - we won't get a convergence otherwise 
                self._inp_img_data = tf.image.per_image_standardization(self._inp_img_data)
                
            # Check if we have a loss value > 0.x and save the (3x3)-data
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            if self._val_oip_loss > loss_limit:
                d_cov[i_cp] = [self._val_oip_loss, cov] 
                if b_print:
                    tf.print("i = ", i_cp, " loss = ", self._val_oip_loss)

        # We restrict the number to those 8 with highest loss 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        if len(d_cov) > 0: 
            self._li_of_flucts = sorted(d_cov.items() , reverse = True,  key=lambda x: x[1][0])
            # print("num of relevant covs = ", len(self._li_of_flucts), len(d_cov))   
            print("\nnum of relevant covs = ", len(self._li_of_flucts))   
            self._li_of_flucts = self._li_of_flucts[:num_selected].copy()
            #save( 'li_of_flucts.npy', np.array(self._li_of_flucts, dtype=np.float32) )
   
         save( 'li_of_flucts.npy', self._li_of_flucts)
            # save the enrichment-setting 
            save('li_of_cov_enrichments.npy',self._li_fluct_enrichments)
            
            
            # Check of map really reacted - and check the reconstruction mechanism 
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            if b_check: 
                print("check of map reaction to first selected image")
                cov_t = self._li_of_flucts[0][1][1]
                #print("cov_t-shape = ", cov_t.shape)
                #cov_del = cov_t - cov
                #print("cov_del =\n", cov_del)
                
                fluct0_scale_t = tf.image.resize(cov_t, [28,28], method="bicubic", antialias=True) 
                        
                # Add fluctuation enrichments - if saved
                if b_with_enriched_fluct:
                    
                    # Scaling enrichment flucts with bicubic interpolation to the required image size
                    fluct1_t = self._li_fluct_enrichments[2][0] 
                    fluct2_t = self._li_fluct_enrichments[2][1] 
                    fluct3_t = self._li_fluct_enrichments[2][2] 
                    fluct4_t = self._li_fluct_enrichments[2][3] 
                    
                    fact0_t = self._li_fluct_enrichments[0][0]
                    fact1_t = self._li_fluct_enrichments[0][1]
                    fact2_t = self._li_fluct_enrichments[0][2]
                    fact3_t = self._li_fluct_enrichments[0][3]
                    fact4_t = self._li_fluct_enrichments[0][4]
                    
                    fluct1_scale_t = tf.image.resize(fluct1_t, [28,28], method="bicubic", antialias=True)
                    fluct2_scale_t = tf.image.resize(fluct2_t, [28,28], method="bicubic", antialias=True)
                    fluct3_scale_t = tf.image.resize(fluct3_t, [28,28], method="bicubic", antialias=True)
                    fluct4_scale_t = fluct4_t
                    
                    fluct_scale_t = fact0_t*fluct0_scale_t \
                                 + fact1_t*fluct1_scale_t + fact2_t*fluct2_scale_t \
                                 + fact3_t*fluct3_scale_t + fact4_t*fluct4_scale_t
                    
                else: 
                    fluct_scale_t = fluct0_scale_t
                
                #standardization
                fluct_data_t  = tf.image.per_image_standardization(fluct_scale_t)     
                fluct_data_t  = tf.where(fluct_data_t > 5.e-6, fluct_data_t, tf.zeros_like(fluct_data_t))
                self._initial_inp_img_data = fluct_data_t
                self._inp_img_data         = fluct_data_t
                self._precursor_img        = fluct_data_t
                
                # optimization loop 
                for j in range(self._n_epochs):
                    self._val_oip_loss, self._val_oip_grads = self._iterate([self._inp_img_data])
                    self._inp_img_data += self._val_oip_grads * self._epsilon
                    self._inp_img_data = tf.image.per_image_standardization(self._inp_img_data)
                print("loss for 1st selected img = ", self._val_oip_loss )

            # show the imgs 
            # ~~~~~~~~~~~~~~
            self._display_precursor_imgs(li_axa = li_axa, fig_a = fig_a)
            
        # list contains no patterns 
        else:
            print("No image found !")
    
    
    # Method to display initial fluctuation images identified as objects for OIP creation 
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    def _display_precursor_imgs(self, li_axa = None, fig_a = None):
        '''
        @summary: Method to display up to 8 selected precursor images 
        @version: 0.2, 02.10.2020
        @change: Only some documentation 
        @note: We first 
reconstruct the image from saved data of the large scale fluctuations 
        @note: We then display the images in externally delivered axes-frames of matplotlib
        @requires: A filled set of valid fluctuation patterns in self._li_of_flucts[][][] - determined by a run of _precursor()
        @requires: Information on fluctuation enrichments in self._li_fluct_enrichments[][] - determined by a _precursor() run
        @requires: A set of axes-frames for plotting - preferably defined in a Jupyter cell calling thi smethod 
        @note: Parameters for plotting  
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        @param _li_axa: A Python list of references to external (Jupyter-) axes-frames for plotting 
         '''
        # length of _li_of_flucts[] vs. length of li_axa
        len_cov = len(self._li_of_flucts)
        if li_axa == None or len(li_axa) < len_cov:
            print("Error: The length of the provided list with axes-frames for plotting must be at least ", len_cov )
            sys.exit()
        
        # Loop to reconstruct and display the found precursor images 
        # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        for j in range(len(self._li_of_flucts)):
            print(j, "loss = ", self._li_of_flucts[j][1][0])
            
            # reconstruct the image from the data of the precursor run 
            # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            cov = self._li_of_flucts[j][1][1]
            fluct0_scale_t  = tf.image.resize(cov, [28,28], method="bicubic", antialias=True)        
            
            # add enrichments if defined 
            if len(self._li_fluct_enrichments) > 0: 
                # Scaling enrichment flucts with bicubic interpolation to the required image size
                fluct1_t = self._li_fluct_enrichments[2][0] 
                fluct2_t = self._li_fluct_enrichments[2][1] 
                fluct3_t = self._li_fluct_enrichments[2][2] 
                fluct4_t = self._li_fluct_enrichments[2][3] 
                
                fact0_t = self._li_fluct_enrichments[0][0]
                fact1_t = self._li_fluct_enrichments[0][1]
                fact2_t = self._li_fluct_enrichments[0][2]
                fact3_t = self._li_fluct_enrichments[0][3]
                fact4_t = self._li_fluct_enrichments[0][4]
                
                fluct1_scale_t = tf.image.resize(fluct1_t, [28,28], method="bicubic", antialias=True)
                fluct2_scale_t = tf.image.resize(fluct2_t, [28,28], method="bicubic", antialias=True)
                fluct3_scale_t = tf.image.resize(fluct3_t, [28,28], method="bicubic", antialias=True)
                fluct4_scale_t = fluct4_t
                
                fluct_scale_t = fact0_t*fluct0_scale_t \
                             + fact1_t*fluct1_scale_t + fact2_t*fluct2_scale_t \
                             + fact3_t*fluct3_scale_t + fact4_t*fluct4_scale_t
            else:
                fluct_scale_t = fluct0_scale_t                 
            
            fluct_datx  = tf.image.per_image_standardization(fluct_scale_t)     
            fluct_dat  = tf.where(fluct_datx > 5.e-6, fluct_datx, tf.zeros_like(fluct_datx))
            img = fluct_dat[0, :,:, 0].numpy()
            li_axa[j].imshow(img, cmap=plt.cm.get_cmap('viridis'))
        
        fig_a.canvas.draw()
        return
    
    
    # Method to transform an img tensor into a standard image - used for contrast enhancemant  
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    def _transform_tensor_to_img(self, T_img = None, centre_move = 0.33, fact = 1.0):
        '''
        @summary: Method to transform (standardized) tensor img data into standard img array data 
                  and to apply contrast enhancement(> V0.2)
        @change: V0.2: Additional 
parameers to control contrast enhancement. 
                 We scale the the value distribution, move its center and apply some clipping  
        @note: Clipping is used to remove pixel values outside [0, 255] 
        @version: 0.2, 12.10.2020
        
        @requires: A defined TF2/Keras backend 
        
        @param T_img: The TF2 or keras tensor for image data 
        @param centre_move: A decimal to move the centre of the pixel value distribution  
        
        
        '''
        ay_x = T_img.numpy()  # floating point array  
        
        maxi_o    = np.max(T_img)
        avg_o     = np.mean(T_img)
        mini_o    = np.min(T_img)
        std_dev_o = np.std(T_img)
        print("\nInfos on pixel value distribution during contrast enhancement: ") 
        print("\max_orig = ", maxi_o, " :: avg_orig = ", avg_o, " :: min_orig: ", mini_o) 
        print("std_dev_orig = ", std_dev_o)

        # the following operation should have no effect on standardized images
        ay_x -= ay_x.mean()
        ay_x /= (ay_x.std() + B.epsilon())
        
        maxi    = np.max(ay_x)
        avg     = np.mean(ay_x)
        mini    = np.min(ay_x)
        std_dev = np.std(ay_x)
        print("max_ay = ", maxi, " :: avg_ay = ", avg, " :: min_ay: ", mini) 
        print("std_dev_ay = ", std_dev)
        
        div = fact * 0.5 * ( abs(maxi_o) + abs(mini_o) )
        print("div = ", div)
        ay_x /= div          # scaling  
        ay_x += centre_move  # moving the data center - 0.5 would move of the distribution into [0,1]
        #                    # smaller values emphasize light/dark contratss 
        maxi = np.max(ay_x)
        avg  = np.mean(ay_x)
        mini = np.min(ay_x)
        std_dev = np.std(ay_x)
        print("max_fin = ", maxi, " :: avg_fin = ", avg, " :: min_fin: ", mini) 
        print("std_dev_fin = ", std_dev)
        
        ay_x = np.clip(ay_x, 0, 1)
        
        ay_x *= 255
        ay_x_img = np.clip(ay_x, 0, 255).astype('uint8')
        
        maxi = np.max(ay_x_img)
        avg  = np.mean(ay_x_img)
        mini = np.min(ay_x_img)
        std_dev = np.std(ay_x_img)
        print("max_img = ", maxi, " :: avg_img = ", avg, " :: min_img: ", mini) 
        print("std_dev_img = ", std_dev, "\n")
        
        
        return ay_x_img


 

Links

A simple CNN for the MNIST dataset – XI – Python code for filter visualization and OIP detection

A simple CNN for the MNIST dataset – XII – filter visualization for maps of the first two convolutional layers

In the last article of this series

A simple CNN for the MNIST dataset – XI – Python code for filter visualization and OIP detection
A simple CNN for the MNIST dataset – X – filling some gaps in filter visualization
A simple CNN for the MNIST dataset – IX – filter visualization at a convolutional layer
A simple CNN for the MNIST dataset – VIII – filters and features – Python code to visualize patterns which activate a map strongly
A simple CNN for the MNIST dataset – VII – outline of steps to visualize image patterns which trigger filter maps
A simple CNN for the MNIST dataset – VI – classification by activation patterns and the role of the CNN’s MLP part

I provided some code to create visualizations of “OIPs” (original input pattern). An OIP is a characteristic pattern in an input image to which a selected map of the deepest convolutional layer of CNN reacts strongly. Most of the patterns we found showed some overall large scale structure with sub-structures of smaller dimensions. In many cases the patterns were repeated two or even more times with some spatial distance across the images’s surface. That we got unique and relatively big patterns for the last and deepest Conv layer is not surprising because the maps of this layer cover the original image area with just a few neurons, i.e. with coarse resolution. The related convolutional filters work across relatively large distances. The astonishing ability of deeper layers to detect unique large scale patterns in input images is based on the weighted superposition of filters working on smaller scales together with a reduction of resolution.

To get images of OIPs we fed the trained CNN with input images whose pixel values were statistically distributed. We optimized the pixel values of the input images for a maximum response of selected maps of the third, i.e. deepest convolutional layer. We can, however, apply the same methods also to maps of the first and the second convolutional layers of our CNN. Then we get much simpler patterns – in the sense of repetitions of many small scale elements.

Below I just provide images of OIPs triggering maps of the first two convolution layers without much further comments. I refer to the layer names as discussed in previous articles of this series.

Input image patterns which lead to a maximum activation of the maps of the convolutional layer Conv2D-1

Layer “Conv2D-1” has 32 maps. With simple fluctuations on the length scale of one to two pixels, we can easily create OIP-images for each of the maps.

Most of these images were actually derived from one and the same input image.

Input image patterns which lead to a maximum
activation of the maps of the convolutional layer Conv2D-2

Layer “Conv2D-2” has 32 maps. With simple fluctuations on the length scale of one to two pixels plus some experiments with pixel value fluctuation son longer scales, I could produce OIP-images for we can easily create OIP-images for 51 of the maps. Experiments for the other 13 maps took to long time; the systematic approach with large scale fluctuations, which we discussed thoroughly in previous articles did not help on layer 2. If you look at the images below, you see that it i more likely that we need specific short and middle-scale fluctuations. However, the amount of possible data combinations is just too big for a systematic investigation.

Conclusion

In the course of the last articles we got a nice overview over the kind of patterns to which the maps of the different convolutional layers of a CNN react to. We are well prepared now to turn back to the question of what the ominous “features” of objects in input images really are. In the meantime have a look at another application of filter visualization in the realm of Deep Dreams, which I recently started to discuss in another article series of this blog. Stay tuned and wear masks to avoid the Corona virus! Stay healthy!

Other (previous) articles in this series

A simple CNN for the MNIST dataset – IV – Visualizing the activation output of convolutional layers and maps
A simple CNN for the MNIST dataset – III – inclusion of a learning-rate scheduler, momentum and a L2-regularizer
A simple CNN for the MNIST datasets – II – building the CNN with Keras and a first test
A simple CNN for the MNIST datasets – I – CNN basics

 

Deep Dreams of a CNN trained on MNIST data – I – a first approach based on one selected map of a convolutional layer

It is fun to play around with Convolutional Neural Networks [CNNs] on the level of an dedicated amateur. One of the reasons is the possibility to visualize the output of elementary building blocks of this class of AI networks. The resulting images help to understand CNN algorithms in an entertaining way – at least in my opinion. The required effort is in addition relatively limited: You must be willing to invest a bit of time into programming, but on a quite modest level of difficulty. And you can often find many basic experiments which are in within the reach of limited PC capabilities.

A special area where the visualization of CNN guided processes is the main objective is the field of “Deep Dreams“. Anyone studying AI methods sooner or later stumbles across the somewhat psychedelic, but none the less spectacular images which Google presented in 2016 as a side branch of their CNN research. Today, you can download DeepDream generators from GitHub.

When I read a bit more about “DeepDream” experiments, I quickly learned that people use quite advanced CNN architectures, like Google’s Inception CNNs, and apply them to high resolution images (see e.g. the Book of F. Chollet on “Deep Learning with Keras and Python” and ai.googleblog.com, 2015, inceptionism-going-deeper-into-neural). Even if you pick up an already trained version of an Inception CNN, you need some decent GPU power to do your own experiments. Another questionable point for an interested amateur is: What does one actually learn from applying “generators”, which others have programmed, and what from just following a “user guide” without understanding what a DeepDream SW actually does? Probably not much, even if you produce stunning images after some time…

So, I asked myself: Can one study basic methods of the DeepDream technology with self programmed tools and a simple dataset? Could one create a “DeepDream” visualization with a rather simply structured CNN trained on MNIST data?
The big advantage of the MNIST data set is that the individual samples are small; and the amount of numerical operations, which a related simple CNN must perform on input images, fits well to the capabilities of PC technology – even if the latter is some years old.

After a first look into DeepDream algorithms, I think: Yes, it should be possible. In a way DeepDream experiments are a natural extension of the visualization of CNN filters and maps which I have already discussed in depth in another article series. Therefore, DeepDream visualizations might even help us to better understand how the internal filter of CNNs work and what “features” are. However, regarding the creation of spectacular images we need to reduce our expectations to a reasonably low level:

A CNN trained on MNIST data works with gray images, low resolution and only simple feature patterns. Therefore, we will never produce such impressive images as published by DeepDream artists or by Google. But, we do have a solid chance to grasp some basic principles and ideas of this side-branch of AI with very simplistic tools.

As always in this blog, I explore a new field step-wise and let you as a reader follow me through the learning process. Throughout most of this new series of articles we will use a CNN created with the help of Keras and filter visualization tools which were developed in another article series of this blog. The CNN has been trained on the MNIST data set already.

In this first post we are going to pick just a single selected feature or response map of a deep CNN layer and let it “dream” upon a down-scaled image of roses. Well, “dream“, as a matter of fact, is a misleading expression; but this is true for the whole DeepDream
business – as we shall see. A CNN does not dream; “DeepDream” creation is more to be seen as an artistic discipline using algorithmic image enhancement.

The input image which we shall feed into our CNN today is shown below:

As our CNN works on a resolution level of 28×28 pixels, only, the “dreaming” will occur in a coarse way, very comparable to hallucinations on the blurred vision level of a short-sighted, myopic man. More precisely: Of a disturbed myopic man who works the whole day with images of digits and lets this poor experience enter and manipulate his dreamy visions of nicer things :-).

Actually, the setup for this article’s experiment was a bit funny: I got the input picture of roses from my wife, who is very much interested in art and likes flowers. I am myopic and in my soul still a theoretical physicist, who is much more attracted by numbers and patterns than by roses – if we disregard the interesting fractal nature of rose blossoms for a second :-).

What do DeepDreams based on single maps of trained MNIST CNNs produce?

To rouse your interest a bit or to disappoint you from the start, I show you a typical result of today’s exercise: “Dreams” or “hallucinations” based on MNIST and a selected single map of a deep convolutional CNN layer produce gray scale images with ghost-like “apparitions”.


When these images appeared on my computer screen, I thought: This is fun, indeed! But my wife just laughed – and said “physicists” with a known undertone and something about “boys and toys” …. I hope this will not stop you from reading further. Later articles will, hopefully, produce more “advanced” hallucinations. But as I said: It all depends on your expectations.

But, lets focus: How did I create the simple “dream” displayed above?

Requirements – a CNN and analysis and visualization tools described in another article series of this blog

I shall use results and methods, which I have already explained in another article series. You need a basic understanding of how a CNN works, what convolutional layers, kernel based filters and cost functions are, how we can build simple CNNs with the help of Keras, … – otherwise you will be lost from the beginning.
A simple CNN for the MNIST datasets – I – CNN basics
We also need a CNN, already trained on the MNIST data. I have shown how to build and train a very simple, yet suitable CNN with the help of Keras and Python; see e.g.:
A simple CNN for the MNIST datasets – II – building the CNN with Keras and a first test
A simple CNN for the MNIST dataset – III – inclusion of a learning-rate scheduler, momentum and a L2-regularizer
In addition we need some
code to create input image patterns which trigger response maps or full layers of a CNN optimally. I called such pixel patterns “OIPs”; others call them “features”. I have offered a Python class in the other article series which offers an optimization loop and other methods to work on OIPs and filter visualization.
A simple CNN for the MNIST dataset – XI – Python code for filter visualization and OIP detection

We shall extend this class by further methods throughout our forthcoming work. To develop and run the codes you should have a working Jupyter environment, a virtual Python environment, an IDE like Eclipse with PyDev for building larger code segments and a working Cuda installation for a NVidia graphics card. My 960GTX proved to be fully sufficient for what we are going to do.

Deep “Dream” – or some funny image manipulation?

As it unfortunately happens so often with AI topics: Also in case of the term “DeepDream” the vocabulary is exaggerated and thoroughly misleading. A simple CNN neither thinks nor “dreams” – it is a software manifestation of the results of an optimization algorithm applied to and trained on selected input data. If applied to new input, it will only detect patterns for which it was optimized before. You could also say:

A CNN is a manifestation of learned prejudices.

CNNs and other types of AI networks filter input according to encoded rules which serve a specific purpose and which reflect the properties of the selected training data set. If you ever used the CNN of my other series on your own hand-written images after a training only on the (US-) MNIST images you will quickly see what I mean. The MNIST dataset reflects an American style of writing digits – a CNN trained on MNIST will fail relatively often when confronted with image samples of digits written by Europeans.

Why do I stress this point at all? Because DeepDreams reveal such kinds of “prejudices” in a visible manner. DeepDream technology extracts and amplifies patterns within images, which fit the trained filters of the involved CNN. F. Chollet correctly describes “DeepDream” as an image manipulation technique which makes use of algorithms for the visualization of CNN filters.

The original algorithmic concept for DeepDreams consists of the following steps:

  • Extend your algorithm for CNN filter visualization (= OIP creation) from a specific map to the optimization of the response of complete layers. Meaning: Use the total response of all maps of a layer to define contributions to your cost function. Then mix these contributions in a defined weighted way.
  • Take some image of whatever motive you like and prepare 4 or more down-scaled versions of this image, i.e. versions with different levels of size and resolution below the original size and resolution.
  • Offer the image with the lowest resolution to the CNN as an input image.
  • Loop over all prepared image sizes :
    • Apply your algorithm for filter visualization of all maps and layers to the input image – but only for a very limited amount of epochs.
    • Upscale the resulting output image (OIP-image) to the next level of higher resolution.
    • Add details of the original image with the same resolution to the upscaled OIP-image.
    • Offer the resulting image as a new input image to your CNN.

Readers who followed me through my last series on “a simple CNN for MNIST” should already raise their eyebrows: What if the CNN expects a certain fixed size of of the input image? Well, a good question. I’ll come back to it in a second. For the time being, let us say that we will concentrate more on resolution than on an
actual image size.

The above steps make it clear that we manipulate an image multiple times. In a way we transform the image slowly to improve a layer’s response and repeat the process with growing resolution. I.e., we apply pattern detection and amplification on more and more details – in the end using all available large and small scale filters of the CNN in a controlled way without fully eliminating the original contents.

What to do about the low resolution of MNIST images and the limited capability of a CNN trained on them?

MNIST images have a very low resolution, real images instead a significantly higher one. With our CNN specialized on MNIST input the OIP-creation algorithm only works on (28×28)-images (and with some warnings, maybe, on smaller ones). What to do about it when we work with input images of a size of e.g. 560×560 pixels?

Well, we just work on the given level of resolution! We have three options:

  • We can downsize the input image itself or parts of it to the MNIST dimensions – with the help of a bicubic interpolation. Then our OIP-algorithm has the chance to detect OIPs on the coarse scale and to change the downsized image accordingly. Then we can upscale the result again to the original image size – and add details again.
  • We can split the input image into tiles of size (28×28) and offer these tiles as input to the CNN.
  • We can combine both of the above options.

Its like what a shortsighted human would do: Work with a blurred impression of the full scale image or look at parts of it from a close distance and then reassemble his/her impressions to larger scales.

A first step – apply only one specific map of a convolutional layer on a down-scaled image version

In this article we have a very limited goal for which we do not have to change our tools, yet:

  • Preparation:
    • We choose a map.
    • We downscale the original image to (28×28) by interpolation, upscale the result again by interpolating again (with loss) and calculate the difference to the original full resolution image (all interpolations done in a bicubic way).
  • Loop (4 times or so):
    • We apply the OIP-algorithm on the downscaled input image for a fixed amount of epochs
    • We upscale the result by bicubic interpolation to the original size.
    • We re-add the difference in details.
    • We downscale the result again.

With this approach I try to apply some of the elements of the original algorithm – but just on one scale of coarse resolution. I shall discuss the code for realizing the recipe given above with Python and Jupyter in the next article. For today let us look at some of the ghost like apparitions in the dreams for selected maps of the 3rd convolutional layer; see:
A simple CNN for the MNIST dataset – IX – filter visualization at a convolutional layer

DeepDreams based on selected maps of the 3rd convolutional layer of a CNN trained on MNIST data

With the image sections displayed below I have tried to collect results for different maps which focus on certain areas of the input image (with the exception of the first image section).

The first two images of each row display the detected OIP-patterns on the (28×28) resolution level with pixel values encoded in a (viridis) color-map; the third image in gray scale. The fourth image reveals the dream on the blurry vision level – up-scaled and interpolated to the original image size. You may still detect traces of the original rose blossoms i these images. The last two images of each row display the results
after re-adding details of the original image and an adjustment of the width of the value distribution. The detected and enhanced pattern then turns into a whitey, ghostly shadow.

I have given each section a fancy headline.

I never promised you a rose garden …

“Getting out …”

“Donut …”

“Curls to form a 3 …”

“Two of them …”

“The creepy roots of it all …”

“Look at me …”

“A hidden opening …”

“Soft is something different …”

“Central separation …”

Conclusion: A CNN
detects patterns or parts of patterns it was trained for in any kind of offered input …

You can compare the results to some input patterns (OIPs) which strongly trigger individual maps on the 3rd convolutional layer; you will detect similarities. E.g. four OIP- or feature patterns to which map 56 reacts strongly, look like:

Filter visualization 1 for CNN map 56Filter visualization 2 for CNN map 56Filter visualization 3 for CNN map 56Filter visualization 4 for CNN map 56

This explains the basic shape of the “apparition” in the first “dream”:

This proves that the filters of a trained CNN actually detect patterns, which proved to be useful for a certain training purpose, in any kind of input which shows some traces of such patterns. A CNN simply does not “know” better: If you only have a hammer to interact with the world, everything becomes a nail to you in the end – this is the level of stupidity on which a CNN algorithm works. And it actually is a fundamental ingredient of DeepDream image manipulation – a transportation of learned patterns or prejudices to an environment outside the original training context.

In the next article
Deep Dreams of a CNN trained on MNIST data – II – some code for pattern carving
I provide the code for creating the above images.

Further articles in this series

Deep Dreams of a CNN trained on MNIST data – II – some code for pattern carving
Deep Dreams of a CNN trained on MNIST data – III – catching dream patterns at smaller length scales