Initial commit.

.gitignore

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+.DS_Store
+node_modules
+test/out*.png

.npmignore

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+*
+!index.js

README.md

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+# FFmpeg Image Diff
+An image diffing library using [FFmpeg](https://www.ffmpeg.org/).  
+Creates an image showing perceptual differences and returns
+[SSIM](https://en.wikipedia.org/wiki/Structural_similarity) data.
+
+## Install
+
+```sh
+npm install ffmpeg-image-diff
+```
+
+## Usage
+
+Displaying
+[SSIM](https://en.wikipedia.org/wiki/Structural_similarity) data only:
+```js
+const imgDiff = require('ffmpeg-image-diff')
+
+imgDiff(
+  referenceImage,     // e.g. 'test/lenna.png'
+  comparisonImage     // e.g. 'test/lenna-edit.png'
+).then((ssim) => {
+  console.log(ssim)
+}).catch((error) => {
+  console.error(error)
+})
+```
+
+Creating a differential image with default options:
+```js
+const imgDiff = require('ffmpeg-image-diff')
+
+imgDiff(
+  referenceImage,     // e.g. 'test/lenna.png'
+  comparisonImage,    // e.g. 'test/lenna-edit.png'
+  outputImage,        // e.g. 'test/out.png'
+  {
+    ssim: true,       // true or false
+    similarity: 0.01, // 1.0 - 0.01
+    blend: 1.0,       // 1.0 - 0.0
+    opacity: 0.1,     // 1.0 - 0.0
+    color: 'pink'     // pink, yellow, green, blue or ''
+  }
+).then((ssim) => {
+  console.log(ssim)
+}).catch((error) => {
+  console.error(error)
+})
+```
+
+## Options
+
+### ssim
+If set to `false`, disables
+[SSIM](https://en.wikipedia.org/wiki/Structural_similarity) calculation.  
+*Default:* `true`
+
+### similarity
+Defines the threshold to identify image differences.  
+`0.01` matches slight differences, while `1.0` only matches stark contrast.  
+*Range:* `1.0 - 0.01`  
+*Default:* `0.01`
+
+### blend
+Blend percentage for the differential pixels.  
+Higher values result in semi-transparent pixels, with a higher transparency the
+more similar the pixels color is to the original color.  
+*Range:* `1.0 - 0.0`  
+*Default:* `1.0`
+
+### opacity
+Opacity of the reference image as backdrop for the differential image.  
+Higher values result in a more opaque background image.  
+*Range:* `1.0 - 0.0`  
+*Default:* `0.1`
+
+### color
+The color balance of the differential pixels.  
+An empty string displays the default differential pixels.  
+*Set:* `['pink', 'yellow', 'green', 'blue', '']`  
+*Default:* `'pink'`
+
+## Samples
+
+### Reference image
+![Lenna](test/lenna.png)
+
+### Comparison image
+![Lenna Edit](test/lenna-edit.png)
+
+### Output image
+![Lenna Diff](test/lenna-diff.png)
+
+## License
+Released under the [MIT license](https://opensource.org/licenses/MIT).
+
+## Author
+[Sebastian Tschan](https://blueimp.net/)

index.js

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+'use strict'
+
+/*
+ * An image diffing library using FFmpeg.
+ * Creates an image showing perceptual differences and returns SSIM data.
+ *
+ * Tested with FFmpeg versions 3.0 (Linux) and 3.2 (OSX).
+ *
+ * For documentation on the image filters used, please see
+ * https://ffmpeg.org/ffmpeg-filters.html
+ *
+ * On the definition of SSIM, please see
+ * https://en.wikipedia.org/wiki/Structural_similarity
+ *
+ * Copyright 2016, Sebastian Tschan
+ * https://blueimp.net
+ *
+ * Licensed under the MIT license:
+ * https://www.opensource.org/licenses/MIT
+ */
+
+function ffmpegImageDiff (refImg, cmpImg, args) {
+  return new Promise((resolve, reject) => {
+    require('child_process').execFile(
+      'ffmpeg',
+      [
+        '-loglevel',
+        'error',
+        '-i',
+        refImg,
+        '-i',
+        cmpImg
+      ].concat(args),
+      function (error, stdout, stderr) {
+        if (error) {
+          return reject(error)
+        }
+        // SSIM log output has the following format:
+        // n:1 R:x.xxxxxx G:x.xxxxxx B:x.xxxxxx All:x.xxxxxx (xx.xxxxxx)
+        // We only keep the R, G, B and All values and turn them into an object:
+        resolve(stdout.split(' ').slice(1, -1).reduce((obj, val) => {
+          const tupel = val.split(':')
+          obj[tupel[0]] = parseFloat(tupel[1])
+          return obj
+        }, {}))
+      }
+    ).on('error', reject)
+  })
+}
+
+module.exports = function (refImg, cmpImg, outImg, opts) {
+  if (!outImg) {
+    // Resolve with the SSIM stats without creating a differential image:
+    return ffmpegImageDiff(refImg, cmpImg, [
+      '-filter_complex',
+      'ssim=stats_file=-',
+      '-f',
+      'null',
+      '-'
+    ])
+  }
+  const options = {
+    ssim: true,       // true or false
+    similarity: 0.01, // 1.0 - 0.01
+    blend: 1.0,       // 1.0 - 0.0
+    opacity: 0.1,     // 1.0 - 0.0
+    color: 'pink'     // pink, yellow, green, blue, '', or FFmpeg colorbalance
+  }
+  if (opts) Object.assign(options, opts)
+  const ssim = options.ssim
+    ? 'ssim=stats_file=-[ssim];[ssim][1]'
+    : ''
+  const colorkey = 'format=rgba,colorkey=white' +
+    `:similarity=${options.similarity}:blend=${options.blend}`
+  let colorbalance = 'colorbalance='
+  switch (options.color) {
+    case 'pink':
+      colorbalance += `rs=1:gs=-1:bs=1:rm=1:gm=-1:bm=1:rh=1:gh=-1:bh=1`
+      break
+    case 'yellow':
+      colorbalance += `rs=1:gs=1:bs=-1:rm=1:gm=1:bm=-1:rh=1:gh=1:bh=-1`
+      break
+    case 'green':
+      colorbalance += `rs=-1:gs=1:bs=-1:rm=-1:gm=1:bm=-1:rh=-1:gh=1:bh=-1`
+      break
+    case 'blue':
+      colorbalance += `rs=-1:gs=-1:bs=1:rm=-1:gm=-1:bm=1:rh=-1:gh=-1:bh=1`
+      break
+    default:
+      colorbalance += options.color
+  }
+  // Create a differential image with transparent background.
+  // The differences are highlighted with the given colorbalance:
+  const diff = `blend=all_mode=phoenix,${colorkey},${colorbalance}[diff];`
+  // Use the reference file as background with the given opacity:
+  const bg = options.opacity < 1
+    ? `format=rgba,colorchannelmixer=aa=${options.opacity}[bg];[bg]`
+    : ''
+  // Overlay the background with the diff:
+  const overlay = `[0]${bg}[diff]overlay=format=rgb`
+  // Create a differential image with the given arguments:
+  return ffmpegImageDiff(refImg, cmpImg, [
+    '-filter_complex',
+    `${ssim}${diff}${overlay}`,
+    '-y',
+    outImg
+  ])
+}

package.json

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+{
+  "name": "ffmpeg-image-diff",
+  "version": "0.0.0",
+  "title": "FFmpeg Image Diff",
+  "description": "An image diffing library using FFmpeg. Creates an image showing perceptual differences and returns SSIM data.",
+  "keywords": [
+    "ffmpeg",
+    "image",
+    "diff",
+    "ssim"
+  ],
+  "homepage": "https://github.com/blueimp/node-ffmpeg-image-diff",
+  "author": {
+    "name": "Sebastian Tschan",
+    "url": "https://blueimp.net"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/blueimp/node-ffmpeg-image-diff.git"
+  },
+  "license": "MIT",
+  "engines": {
+    "node": ">=6.0.0"
+  },
+  "devDependencies": {
+    "standard": "8.6.0"
+  },
+  "scripts": {
+    "lint": "standard *.js test/*.js",
+    "unit": "./test/run.js",
+    "test": "npm run lint && npm run unit",
+    "preversion": "npm test",
+    "postversion": "git push --tags origin HEAD && npm publish"
+  },
+  "main": "index.js"
+}

test/run.js

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+#!/usr/bin/env node
+
+'use strict'
+
+process.chdir(__dirname)
+
+// Throw for any unhandled rejections in Promise chains:
+process.on('unhandledRejection', function (reason) { throw reason })
+
+const assert = require('assert')
+const imgDiff = require('../index')
+
+const refImg = 'lenna.png'
+const cmpImg = 'lenna-edit.png'
+
+function test (outImg, options) {
+  return imgDiff(refImg, cmpImg, outImg, options)
+    .then((result) => {
+      assert.ok(result)
+      if (options && options.ssim === false) {
+        assert.deepEqual(result, {})
+      } else {
+        assert.strictEqual(typeof result.R, 'number')
+        assert.strictEqual(typeof result.G, 'number')
+        assert.strictEqual(typeof result.B, 'number')
+        assert.strictEqual(typeof result.All, 'number')
+      }
+    })
+}
+
+test() // SSIM only
+  .then(() => test('out.png')) // Default options (color: 'pink')
+  .then(() => test('out-color-yellow.png', {color: 'yellow'}))
+  .then(() => test('out-color-green.png', {color: 'green'}))
+  .then(() => test('out-color-blue.png', {color: 'blue'}))
+  .then(() => test('out-color-empty.png', {color: ''}))
+  .then(() => test('out-similarity-1.png', {similarity: 1}))
+  .then(() => test('out-blend-0.png', {blend: 0}))
+  .then(() => test('out-opacity-0.png', {opacity: 0}))
+  .then(() => test('out-opacity-1.png', {opacity: 1}))
+  .then(() => test('out-ssim-false.png', {ssim: false}))