feat: ability to compare images by regions

index.js

@@ -8,10 +8,8 @@ const areColorsSame = require('./lib/same-colors');
 const AntialiasingComparator = require('./lib/antialiasing-comparator');
 const IgnoreCaretComparator = require('./lib/ignore-caret-comparator');
 const utils = require('./lib/utils');
-const readPair = utils.readPair;
-const getDiffPixelsCoords = utils.getDiffPixelsCoords;
-
-const JND = 2.3; // Just noticeable difference if ciede2000 >= JND then colors difference is noticeable by human eye
+const {getDiffPixelsCoords} = utils;
+const {JND} = require('./lib/constants');
 
 const makeAntialiasingComparator = (comparator, png1, png2, opts) => {
     const antialiasingComparator = new AntialiasingComparator(comparator, png1, png2, opts);
@@ -120,36 +118,40 @@ const getToleranceFromOpts = (opts) => {
 const prepareOpts = (opts) => {
     opts.tolerance = getToleranceFromOpts(opts);
 
-    _.defaults(opts, {
+    return _.defaults(opts, {
         ignoreCaret: true,
         ignoreAntialiasing: true,
         antialiasingTolerance: 0
     });
 };
 
-const getMaxDiffBounds = (first, second) => ({
-    left: 0,
-    top: 0,
-    right: Math.max(first.width, second.width) - 1,
-    bottom: Math.max(first.height, second.height) - 1
-});
+const getMaxDiffBounds = (first, second) => {
+    const {x: left, y: top} = first.getActualCoord(0, 0);
+
+    return {
+        left,
+        top,
+        right: left + Math.max(first.width, second.width) - 1,
+        bottom: top + Math.max(first.height, second.height) - 1
+    };
+};
 
-module.exports = exports = function looksSame(reference, image, opts, callback) {
+module.exports = exports = function looksSame(image1, image2, opts, callback) {
     if (!callback) {
         callback = opts;
         opts = {};
     }
 
-    prepareOpts(opts);
+    opts = prepareOpts(opts);
+    [image1, image2] = utils.formatImages(image1, image2);
 
-    readPair(reference, image, (error, pair) => {
+    utils.readPair(image1, image2, (error, pair) => {
         if (error) {
             return callback(error);
         }
 
-        const first = pair.first;
-        const second = pair.second;
-        const refImg = {size: {width: pair.first.width, height: pair.first.height}};
+        const {first, second} = pair;
+        const refImg = {size: {width: first.width, height: first.height}};
         const metaInfo = {refImg};
 
         if (first.width !== second.width || first.height !== second.height) {
@@ -167,21 +169,21 @@ module.exports = exports = function looksSame(reference, image, opts, callback)
     });
 };
 
-exports.getDiffArea = function(reference, image, opts, callback) {
+exports.getDiffArea = function(image1, image2, opts, callback) {
     if (!callback) {
         callback = opts;
         opts = {};
     }
 
-    prepareOpts(opts);
+    opts = prepareOpts(opts);
+    [image1, image2] = utils.formatImages(image1, image2);
 
-    readPair(reference, image, (error, pair) => {
+    utils.readPair(image1, image2, (error, pair) => {
         if (error) {
             return callback(error);
         }
 
-        const first = pair.first;
-        const second = pair.second;
+        const {first, second} = pair;
 
         if (first.width !== second.width || first.height !== second.height) {
             return process.nextTick(() => callback(null, getMaxDiffBounds(first, second)));
@@ -200,9 +202,11 @@ exports.getDiffArea = function(reference, image, opts, callback) {
 };
 
 exports.createDiff = function saveDiff(opts, callback) {
-    prepareOpts(opts);
+    opts = prepareOpts(opts);
+
+    const [image1, image2] = utils.formatImages(opts.reference, opts.current);
 
-    readPair(opts.reference, opts.current, (error, {first, second}) => {
+    utils.readPair(image1, image2, (error, {first, second}) => {
         if (error) {
             return callback(error);
         }

lib/constants.js

@@ -0,0 +1,7 @@
+'use strict';
+
+module.exports = {
+    JND: 2.3, // Just noticeable difference if ciede2000 >= JND then colors difference is noticeable by human eye
+    REQUIRED_IMAGE_FIELDS: ['source', 'boundingBox'],
+    REQUIRED_BOUNDING_BOX_FIELDS: ['left', 'top', 'right', 'bottom']
+};

lib/diff-area.js

@@ -6,7 +6,7 @@ module.exports = class DiffArea {
         this._updated = false;
     }
 
-    update(x, y) {
+    update({x, y}) {
         const {left, top, right, bottom} = this._diffArea;
 
         this._diffArea = {

lib/png/bounded-png.js

@@ -0,0 +1,35 @@
+'use strict';
+
+const PNGImage = require('./png');
+
+module.exports = class BoundedPNGImage extends PNGImage {
+    constructor(png, boundingBox) {
+        super(png);
+
+        this._boundingBox = boundingBox;
+    }
+
+    getPixel(x, y) {
+        const {x: actX, y: actY} = this.getActualCoord(x, y);
+
+        return super.getPixel(actX, actY);
+    }
+
+    setPixel(x, y, color) {
+        const {x: actX, y: actY} = this.getActualCoord(x, y);
+
+        super.setPixel(actX, actY, color);
+    }
+
+    getActualCoord(x, y) {
+        return {x: x + this._boundingBox.left, y: y + this._boundingBox.top};
+    }
+
+    get width() {
+        return this._boundingBox.right - this._boundingBox.left + 1;
+    }
+
+    get height() {
+        return this._boundingBox.bottom - this._boundingBox.top + 1;
+    }
+};

lib/png/index.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const fs = require('fs');
+const {PNG} = require('pngjs');
+const OriginalPNG = require('./original-png');
+const BoundedPNG = require('./bounded-png');
+
+exports.create = (png, {boundingBox} = {}) => {
+    return boundingBox
+        ? BoundedPNG.create(png, boundingBox)
+        : OriginalPNG.create(png);
+};
+
+exports.fromFile = (filePath, opts = {}, callback) => {
+    fs.readFile(filePath, (error, data) => {
+        error
+            ? callback(error, null)
+            : exports.fromBuffer(data, opts, callback);
+    });
+};
+
+exports.fromBuffer = (buffer, opts = {}, callback) => {
+    const png = new PNG();
+    png.parse(buffer, (error) => {
+        error
+            ? callback(error, null)
+            : callback(null, exports.create(png, opts));
+    });
+};
+
+exports.empty = (width, height) => exports.create(new PNG({width, height}));

lib/png/original-png.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const PNGImage = require('./png');
+
+module.exports = class OriginalPNGImage extends PNGImage {
+    getActualCoord(x, y) {
+        return {x, y};
+    }
+
+    get width() {
+        return this._png.width;
+    }
+
+    get height() {
+        return this._png.height;
+    }
+};