pixelmatch
The smallest, simplest JavaScript pixel-level image comparison library
...Features accurate anti-aliased pixels detection and perceptual color difference metrics. Inspired by Resemble.js and Blink-diff. Unlike these libraries, pixelmatch is around 150 lines of code, has no dependencies, and works on raw typed arrays of image data, so it's blazing fast and can be used in any environment (Node or browsers). Compares two images, writes the output diff and returns the number of mismatched pixels.