How to store effectively pictures with minimal differences

I'd like to store effectively list of images that have minimal differences (e.g. photo with small marks here and there) and I'd like to store them effectively on the disk (minimum disk space occupied) but loss-lessly.

I tried to use list of png files and convert them to MNG, but the file size is terrible -- I was expecting some save-only-layer-difference way of storing data :)

Any suggestions how to store similar images lossless ly in single file with minimum size?

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