image-equal

Test if two images are equal. Useful for organising baseline tests for visual components.

Usage

let t = require('tape')
let equal = require('image-equal')
let pixels = require('image-pixels')

t('image test', async t => {
	t.ok(equal(await pixels('./a.png'), canvasA))
	t.ok(equal(await pixels('./b.png'), canvasB, {threshold: .2}))

	// display diff to console in case of mismatch
	t.ok(equal(await pixels('./c.png'), canvasC, true))

	// compare two pixel arrays
	t.ok(equal([0,0,0,255,255,255,255,255], [0,0,0,255,255,255,255,255]))

	t.end()
})

equal(imageA, imageB, diff?, threshold=0.1|options?)

Takes two images and returns true if they're similar and false otherwise, optionally sending diff stats to diff output. options can adjust comparison logic.

imageA, imageB

Shoud be actual image data container, one of:

• Canvas, Context2D, WebGLContext
• ImageData or Object {data: Uint8Array, width, height}
• DataURL or base64 string
• Image, Video, ImageBitmap with resolved data
• Array, Array of Arrays, Uint8Array, FloatArray with raw pixels
• ArrayBuffer, Buffer
• Ndarray

To use async image source, like URL, path, ImageBitmap, Promise, incomplete Image/Video, Stream, Blob and alike, use image-pixels:

const equal = require('image-equal')
const load = require('image-pixels')
equal(await load('./a.png'), await load('./b.png')),

diff

Can be one of:

Type	Meaning
Bool	Show diff data to console, by default false.
console	Send diff data to console, same as true.
Canvas2D, Context2D	Put diff pixels to a canvas.
document, Element	Create a canvas in document/element with diff pixels.
filename String	Write diff data to a file or filepath. In browser downloads the file.
ImageData	Write diff data to ImageData object.
Array, TypedArray	Write diff pixels data to target array.
Stream	Send data to stream, eg. process.stdout (acts the same as console).
Function	Call function with diff data object.
Object	Put diff stats into object: diff.data for diff pixels, diff.count for number of diff pixels, diff.ids for diff pixel ids and diff.amount for amount of difference between images, 0..1.

options

Property	Meaning
antialias	Include antialias, by default false.
threshold	Sensitivity to px difference, 0 - intolerant, 1 - not sensitive. By default 0.1.
clip	A sub-area to compare, rectangle [left, top, width, height].

See also

• image-pixels — load or save pixel data from any source.
• image-output — output pixels data into any destination.
• pixelmatch − fuzzy image comparison tool.

Credits

© 2018 Dmitry Yv. MIT License