| const fs = require('fs'); |
| const PNG = require('pngjs').PNG; |
| const pixelmatch = require('pixelmatch'); |
| |
| function readPNG(path) { |
| return new Promise(resolve => { |
| fs.createReadStream(path) |
| .pipe(new PNG()) |
| .on('parsed', function () { |
| resolve({ |
| data: this.data, |
| width: this.width, |
| height: this.height |
| }); |
| }); |
| }); |
| } |
| |
| module.exports.compareImage = function (targetPath, sourcePath, threshold = 0.1) { |
| if (!fs.existsSync(targetPath)) { |
| return true; |
| } |
| |
| return Promise.all([ |
| readPNG(targetPath), |
| readPNG(sourcePath) |
| ]).then(([expectedImg, actualImg]) => { |
| let width = expectedImg.width; |
| let height = expectedImg.height; |
| if ( |
| (width !== actualImg.width) |
| || (height !== actualImg.height) |
| ) { |
| return {diffRatio: 1} |
| } |
| const diffPNG = new PNG({width, height}); |
| let diffPixelsCount = pixelmatch(expectedImg.data, actualImg.data, diffPNG.data, width, height, { |
| threshold |
| }); |
| let totalPixelsCount = width * height; |
| |
| return { |
| diffRatio: diffPixelsCount / totalPixelsCount, |
| diffPNG |
| }; |
| }); |
| } |