set:~/images> compare 
Attempting to read /home/brudy/images/img1.pgm and
                   /home/brudy/images/img2.pgm
Warning: (pnmReadHeader) Maxval is not 255, but 63
ncols 320 nrows 240 maxval 63
Warning: (pnmReadHeader) Maxval is not 255, but 63
ncols 320 nrows 240 maxval 63
Images successfully read. Their size is 320 by 240
Matching scanlines independently...
     scanline 0
     scanline 50
     scanline 100
     scanline 150
     scanline 200
Done.  Independent processing took  2.3 seconds of processor time.
Postprocessing disparity map...
Done.  Postprocessing took  0.6 seconds of processor time.
Total processor time was  3.0 seconds.
Writing to dm.pgm and dd.pgm