Adding Few more which I have used recently & are good for image pixel comparisions:
PhantomCSS takes screenshots captured by CasperJS and compares them to baseline images using Resemble.js to test for rgb pixel differences. PhantomCSS then generates image diffs to help you find the cause.
2. FBSnapshotTestCase (Uses XCTest):
FBSnapshotTestCase uses a “snapshot test case” that takes a configured UIView or CALayer and uses the renderInContext: method to get an image snapshot of its contents. It compares this snapshot to a “reference image” stored in your source code repository and fails the test if the two images don't match.
Refer : https://github.com/facebookarchive/ios-snapshot-test-case
3. Gemini (Uses JS DSL):
Gemini is a utility for regression testing the visual appearance of web pages. Check it out on Getting Started with Gemini : http://www.kevinlamping.com/hands-on-visual-regression-testing/3-Gemini/1-install.html
4. Needle (Uses Python):
Needle is a tool for testing visuals with Selenium and nose.
It checks that visuals (CSS/fonts/images/SVG/etc.) render correctly by taking screenshots of portions of a website and comparing them against known good screenshots. It also provides tools for testing calculated CSS values and the position of HTML elements. See example in the Visual Regression Testingpost.
Refer : https://github.com/python-needle/needle