How to save an image, losslessly compressed, with multiple layers (like with Photoshop PSD but rather an open format), with OpenCV cv2 or PIL/Pillow ?
Note: Is seems that TIFF format can do this (see this answer), but as I remember TIFF have lower compression ratio than PNG.
Pseudo code:
import cv2
cv2.imwrite('test.tiff', layer1, layer2, layer3)
The most comprehensive support for reading/writing TIFFs in Python is almost certainly tifffile.
If you want lossless compression, try LZW and ZIP.