> (define bush256 (read-image "bush256.pgm")) > bush256 #<image: rows = 256 cols = 256> > > (define bozo64 (read-image "bozo64.pgm")) > bozo64 #<image: rows = 64 cols = 64> > > (define watermark1 (make-watermark bozo64 1 0.5)) > watermark1 #<image: rows = 128 cols = 128> > > (define watermark2 (make-watermark bozo64 2 0.5)) > watermark2 #<image: rows = 256 cols = 256> > > (write-image (insert-watermark bush256 watermark2) "watermarked-bush.pgm") > (read-image "watermarked-bush.pgm") #<image: rows = 256 cols = 256> > > (recover-watermark (read-image "watermarked-bush.pgm") bush256 0) #<image: rows = 256 cols = 256> > > (recover-watermark (read-image "watermarked-bush.pgm") bush256 1) #<image: rows = 256 cols = 256> > > (recover-watermark (read-image "watermarked-bush.pgm") bush256 2) #<image: rows = 256 cols = 256> >