data watermarking method

[dkazanc]

A new method to satisfy the following issue in httomo. Essentially we need to put a stamp on the image in places where it will be well visible, therefore the following should be considered:

• consider underlying intensity values so that the mask is visible, e.g. if the background is zero the mask is 1 and vice versa
• the size of the printed digits relative to the size of the data
• position of the digits relative to the data size

It seems to me that the easiest way will be to generate an image using those pillow tutorials
https://stackoverflow.com/questions/67965574/watermarking-image-using-pillow https://www.tutorialspoint.com/python_pillow/python_pillow_creating_a_watermark.htm

then threshold it and obtain the mask with which the input array is multiplied considering the conditions above.

[dkazanc]

the issue should be in httomolib, this is not a gpu method.