I was wondering if anyone knows of any software that will allow image comparisons to show differences between two images (BMP or TIFF) - preferably with some numeric statistics. I am trying to do an analysis of individual frames from a movie that has been reduced using the main encoders and transcoders to see which gives the closest match to the original.

I am aware of PSNR and SSIM to compare the video stream completely but I want a simple single frame test too.

Any help would be appreciated.