Created
March 1, 2019 10:06
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Get diff from 2 PNGs and recreate them
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| const PNG = require('pngjs').PNG; | |
| const fs = require('fs'); | |
| const img1 = fs.createReadStream('./4a.png').pipe(new PNG()).on('parsed', doneReading); | |
| const img2 = fs.createReadStream('./4b.png').pipe(new PNG()).on('parsed', doneReading); | |
| let filesRead = 0; | |
| function applyPixels(data1, data2, width, height, result) { | |
| for (let y = 0; y < height; y++) { | |
| for (let x = 0; x < width; x++) { | |
| const pos = (y * width + x) * 4; | |
| xorPixels(data1, data2, pos, result); | |
| } | |
| } | |
| } | |
| function xorPixels(data1, data2, pos, result) { | |
| result[pos + 0] = data1[pos + 0] ^ data2[pos + 0]; | |
| result[pos + 1] = data1[pos + 1] ^ data2[pos + 1]; | |
| result[pos + 2] = data1[pos + 2] ^ data2[pos + 2]; | |
| result[pos + 3] = data1[pos + 3] ^ data2[pos + 3]; | |
| } | |
| function doneReading() { | |
| if (++filesRead < 2) return; | |
| const {width, height} = img1; | |
| const result = new Buffer(height * width * 4); // 4 because R, G, B and alpha | |
| // get diff buffer from two images | |
| applyPixels(img1.data, img2.data, width, height, result); | |
| // now we have result matrix. and we can recreate both images | |
| // recreate image1 from image2 | |
| const png1FromPng2 = new PNG({width, height}); | |
| applyPixels(img2.data, result, width, height, png1FromPng2.data); | |
| png1FromPng2.pack().pipe(fs.createWriteStream('diff1from2.png')); | |
| // recreate image2 from image1 | |
| const png2FromPng1 = new PNG({width, height}); | |
| applyPixels(img1.data, result, width, height, png2FromPng1.data); | |
| png2FromPng1.pack().pipe(fs.createWriteStream('diff2from1.png')); | |
| } |
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