> (define rad (read-image "lisa.pgm")) > lisa #<image: rows = 256 cols = 256> >

> (define negative-upper-left (- 255 (image-crop lisa 32 32 128 128))) > negative-upper-left #<image: rows = 128 cols = 128> >

> (define lower-right (image-crop lisa 128 128 128 128))) > lower-right #<image: rows = 128 cols = 128> >

> (define ls (find-overlap-region negative-upper-left lower-right)) > (car ls) #<image: rows = 96 cols = 96> >

> (cadr ls) #<image: rows = 96 cols = 96> >