Detecting image equality at different resolutions

Question

I\'m trying to build a script to go through my original, high-res photos and replace the old, low-res ones I uploaded to Flickr before I had a pro account.

For many of t

Answer 1

I'd recommend scripting a solution off of ImageMagick. The following (from the documentation on comparing images with IM) would output a comparative value that you can use.

convert image1 image2 \
        -compose difference -composite -colorspace gray miff:- |\
  identify -verbose - |\
    sed -n '/^.*Mean: */{s//scale=2;/;s/(.*)//;s/$/*100\/32768/;p;q;}' | bc