Consider rescaling (binning) large images

A binning 2x2 on large images would already speed up the program and reduced memory usage

created branch 21-consider-rescaling-binning-large-images to address this issue

mentioned in merge request !41 (merged)

mentioned in merge request !44 (merged)

mentioned in merge request !45 (merged)

mentioned in merge request !46 (merged)

mentioned in merge request !47 (merged)