system ('convert -depth 8 -crop %dx%d+0+0 %s %s/crop1.png' % (dims + (old, dir)))
system ('convert -depth 8 -crop %dx%d+0+0 %s %s/crop2.png' % (dims + (new, dir)))
system ('convert -depth 8 -crop %dx%d+0+0 %s %s/crop1.png' % (dims + (old, dir)))
system ('convert -depth 8 -crop %dx%d+0+0 %s %s/crop2.png' % (dims + (new, dir)))