LooksSame

Pure node.js library for comparing PNG-images, taking into account human color perception. It is created specially for the needs of visual regression testing for gemini utility, but can be used for other purposes.

Comparing images

var looksSame = require('looks-same');

looksSame('image1.png', 'image2.png', function(error, equal) {
    //equal will be true, if images looks the same
});

Parameters can be paths to files or buffer with compressed png image.

By default, it will detect only noticeable differences. If you wish to detect any difference, use strict options:

looksSame('image1.png', 'image2.png', {strict: true}, function(error, equal) {
    ...
});

You can also adjust the ΔE value that will be treated as error in non-strict mode:

looksSame('image1.png', 'image2.png', {tolerance: 5}, function(error, equal) {
    ...
});

Default tolerance in non-strict mode is 2.3 which is enough for the most cases. Setting tolerance to 0 will produce the same result as strict: true, but strict mode is faster. Attempt to set tolerance in strict mode will produce an error.

For visual regression tasks it may be useful to ignore text caret in text input elements. You can do it with ignoreCaret option.

looksSame('image1.png', 'image2.png', {ignoreCaret: true}, function(error, equal) {
    ...
});

Both strict and ignoreCaret can be set independently of one another.

Building diff image

looksSame.createDiff({
    reference: '/path/to/reference/image.png',
    current: '/path/to/reference/image.png',
    diff: '/path/to/save/diff/to.png',
    highlightColor: '#ff00ff', //color to highlight the differences
    strict: false,//strict comparsion
    tolerance: 2.5
}, function(error) {
});