pixelmatch - The smallest, simplest and fastest JavaScript pixel-level image comparison library
XnViewMP is the enhanced version to XnView. It is a powerful cross-platform media browser, viewer and converter. Compatible with more than 500 formats.
Resemble.js analyses and compares images with HTML5 canvas and JavaScript.
BPG (Better Portable Graphics) is a new image format. Its purpose is to replace the JPEG image format when quality or file size is an issue. Its main advantages are: