a command-line tool for pixel-sorting png images.
$ make
$ ./pixelsort [options] <in.png> <out.png>
options:
-o, --orientation [row|column|both] (row)
-m, --method [light|dark|all] (light)
-c, --comparator [avg|mul|max|min|xor] (min)
-t, --threshold [0..255] (210)