Compute the difference between two images. More information: https://netpbm.sourceforge.net/doc/pnmpsnr.html.
pnmpsnr path/to/file1.pnm path/to/file2.pnm
pnmpsnr path/to/file1.pnm path/to/file2.pnm -rgb
nomatch
or match
depending on whether the computing PSNR exceeds n
or not:pnmpsnr path/to/file1.pnm path/to/file2.pnm -target n
pnmpsnr path/to/file1.pnm path/to/file2.pnm -target1 threshold_Y -target2 threshold_Cb -target3 threshold_Cr
pnmpsnr path/to/file1.pnm path/to/file2.pnm -rgb -target1 threshold_red -target2 threshold_green -target3 threshold_blue
pnmpsnr path/to/file1.pnm path/to/file2.pnm -machine