diffImages

import { diffImages, MOST_PICTURES } from 'diffine-react/image';

const result = diffImages([saved, chrome, firefox]);

(pictures: readonly DiffPixels[], options?: DiffImagesOptions) => DiffImagesResult

final DiffImagesResult result = diffImages(<DiffPixels>[saved, chrome, firefox]);

DiffImagesResult diffImages(List<DiffPixels> pictures, [DiffImagesOptions? options])

Three renderings of one screen, four exports of one asset, a saved version against the last five runs. What is wanted there is one frame with every disagreement on it, and a pair has no room for a third. Each picture is compared with the baseline exactly as diffImage would compare it, so every option means what it means there, and a list of two is the same answer in a different shape. DiffImagesOptions is that table with the baseline added to it.

What the list adds is the mask. It is a bit a picture rather than a kind: bit i is set where the picture at i differs from the baseline, so mask[pixel] != 0 is "does anything disagree here" and mask[pixel] & (1 << i) is "does this one". added and removed have no place in it — whose arrival a pixel is depends on which picture is being asked about, and the answer for a list is that they disagree. DiffImagesResult is the whole of what comes back.

A byte holds eight bits, so eight pictures is the most one comparison takes. MOST_PICTURESkMostPictures is that number, and a list shorter than two or longer than it is a RangeError rather than an answer. The pair each picture makes with the baseline is still diffImage, which has no limit.