Barebones Go image differ.
Installation:
$ go get github.com/mtklein/idiff
Usage:
$ idiff <left> <right> [diff.html]
Suggested workflow:
$ <generate known good images in good/>
$ while working ...
$ <generate new images in bad/>
$ idiff good bad && {start,open,xdg-open} diff.html