Untilted*

visual image diff, v0.000000001

#!/usr/bin/env ruby

require "rubygems"
require "RMagick"

original = Magick::Image.read(ARGV[0]).first
new_version = Magick::Image.read(ARGV[1]).first
comparison = original.composite(new_version, Magick::CenterGravity, Magick::DifferenceCompositeOp)
comparison.write("diff.png")

Save in ~/bin, add ‘bin’ to PATH, and use as:

$ vdiff original_version.png new_version.png

and a ‘diff.png’ file highlighting the differences is created.