@lewiswright/vitest-plugin-vis/esm/shared/compare_image.js

Vitest visual testing plugin

import pixelmatch from 'pixelmatch';
import { ssim } from 'ssim.js';
import { convertThresholdUnit } from "./convert_threshold_unit.js";
export function compareImage(img1, img2, output, width, height, options = {}) {
    const pixelDiff = options.comparisonMethod === 'ssim'
        ? compareWithSsim(img1, img2, output, width, height, options.diffOptions)
        : pixelmatch(img1, img2, output, width, height, options.diffOptions);
    const diffAmount = convertThresholdUnit({ failureThresholdType: options.failureThresholdType ?? 'pixel', width, height }, pixelDiff);
    return {
        pass: diffAmount <= (options.failureThreshold ?? 0),
        diffAmount,
    };
}
/**
 * @author This code is based on `jest-image-snapshot` implementation.
 */
function compareWithSsim(img1, img2, output, width, height, diffOptions) {
    const newImage = { data: img1, width: width, height: height };
    const baselineImage = { data: img2, width: width, height: height };
    const { ssim_map, mssim } = ssim(newImage, baselineImage, {
        ssim: 'bezkrovny',
        ...diffOptions,
    });
    // Converts the SSIM value to different pixels based on image width and height
    // conforms to how pixelmatch works.
    const diffPixels = Math.round((1 - mssim) * width * height);
    const diffRgbaPixels = new DataView(output.buffer, output.byteOffset);
    for (let ln = 0; ln !== height; ++ln) {
        for (let pos = 0; pos !== width; ++pos) {
            const rPos = ln * width + pos;
            // initial value is transparent.  We'll add in the SSIM offset.
            // red (ff) green (00) blue (00) alpha (00)
            const diffValue = 0xff000000 +
                Math.floor(0xff *
                    (1 -
                        ssim_map.data[ssim_map.width * Math.round((ssim_map.height * ln) / height) +
                            Math.round((ssim_map.width * pos) / width)]));
            diffRgbaPixels.setUint32(rPos * 4, diffValue);
        }
    }
    return diffPixels;
}