feat: Context.prototype.getImageData (experimental), for https://github.com/gliffy/canvas2svg/issues/3, for https://github.com/zenozeng/p5.js-svg/issues/203

README.md

@@ -26,8 +26,16 @@ ctx.fillRect(100,100,100,100);
 const mySerializedSVG = ctx.getSerializedSvg(); 
 ```
 
+## Tests
+
+https://zenozeng.github.io/p5.js-svg/test/
+
 ## CHANGELOG
 
+## v2.2.0
+
+- feat: Context.prototype.getImageData (experimental) for https://github.com/gliffy/canvas2svg/issues/3 and https://github.com/zenozeng/p5.js-svg/issues/203
+
 ## v2.1.0
 
 - feat: SVGCanvasElement(options)

context.js

@@ -14,6 +14,7 @@
  */
 
 import * as utils from './utils';
+import imageUtils from './image';
 
 export default (function () {
     "use strict";
@@ -1306,12 +1307,24 @@ export default (function () {
         return new DOMPoint(x, y).matrixTransform(this.__transformMatrix)
     }
 
+    /**
+     * 
+     * @param {*} sx The x-axis coordinate of the top-left corner of the rectangle from which the ImageData will be extracted.
+     * @param {*} sy The y-axis coordinate of the top-left corner of the rectangle from which the ImageData will be extracted.
+     * @param {*} sw The width of the rectangle from which the ImageData will be extracted. Positive values are to the right, and negative to the left.
+     * @param {*} sh The height of the rectangle from which the ImageData will be extracted. Positive values are down, and negative are up.
+     * @param {Boolean} options.async Will return a Promise<ImageData> if true, must be set to true
+     * @returns An ImageData object containing the image data for the rectangle of the canvas specified. The coordinates of the rectangle's top-left corner are (sx, sy), while the coordinates of the bottom corner are (sx + sw, sy + sh).
+     */
+    Context.prototype.getImageData = function(sx, sy, sw, sh, options) {
+        return imageUtils.getImageData(this.getSvg(), this.width, this.height, sx, sy, sw, sh, options);
+    };
+
     /**
      * Not yet implemented
      */
     Context.prototype.drawFocusRing = function () {};
     Context.prototype.createImageData = function () {};
-    Context.prototype.getImageData = function () {};
     Context.prototype.putImageData = function () {};
     Context.prototype.globalCompositeOperation = function () {};
 

element.js

@@ -1,4 +1,5 @@
 import Context from './context';
+import imageUtils from './image';
 
 function SVGCanvasElement(options) {
 
@@ -74,45 +75,15 @@ SVGCanvasElement.prototype.toObjectURL = function() {
     return URL.createObjectURL(svg);
 };
 
-SVGCanvasElement.prototype.toDataURL = function(type, options) {
-    var xml = new XMLSerializer().serializeToString(this.svg);
-
-    // documentMode is an IE-only property
-    // http://msdn.microsoft.com/en-us/library/ie/cc196988(v=vs.85).aspx
-    // http://stackoverflow.com/questions/10964966/detect-ie-version-prior-to-v9-in-javascript
-    var isIE = document.documentMode;
-
-    if (isIE) {
-        // This is patch from canvas2svg
-        // IE search for a duplicate xmnls because they didn't implement setAttributeNS correctly
-        var xmlns = /xmlns="http:\/\/www\.w3\.org\/2000\/svg".+xmlns="http:\/\/www\.w3\.org\/2000\/svg/gi;
-        if(xmlns.test(xml)) {
-            xml = xml.replace('xmlns="http://www.w3.org/2000/svg','xmlns:xlink="http://www.w3.org/1999/xlink');
-        }
-    }
-
-    var SVGDataURL = "data:image/svg+xml;charset=utf-8," + encodeURIComponent(xml);
-    if (type === "image/svg+xml" || !type) {
-        return SVGDataURL;
-    }
-    if (type === "image/jpeg" || type === "image/png") {
-        var canvas = document.createElement('canvas');
-        canvas.width = this.width;
-        canvas.height = this.height;
-        var ctx = canvas.getContext('2d');
-        var img = new Image();
-        img.src = SVGDataURL;
-        if (img.complete && img.width > 0 && img.height > 0) {
-            // for chrome, it's ready immediately
-            ctx.drawImage(img, 0, 0);
-            return canvas.toDataURL(type, options);
-        } else {
-            // for firefox, it's not possible to provide sync api in current thread
-            // and web worker doesn't provide canvas API, so
-            throw new Error('svgcanvas.toDataURL() for jpeg/png is only available in Chrome.');
-        }
-    }
-    throw new Error('Unknown type for SVGCanvas.prototype.toDataURL, please use image/jpeg | image/png | image/svg+xml.');
+/**
+ * toDataURL returns a data URI containing a representation of the image in the format specified by the type parameter.
+ * 
+ * @param {String} type A DOMString indicating the image format. The default type is image/svg+xml; this image format will be also used if the specified type is not supported.
+ * @param {Number} encoderOptions A Number between 0 and 1 indicating the image quality to be used when creating images using file formats that support lossy compression (such as image/jpeg or image/webp). A user agent will use its default quality value if this option is not specified, or if the number is outside the allowed range.
+ * @param {Boolean} options.async Will return a Promise<String> if true, must be set to true if type is not image/svg+xml
+ */
+SVGCanvasElement.prototype.toDataURL = function(type, encoderOptions, options) {
+    return imageUtils.toDataURL(this.svg, this.width, this.height, type, encoderOptions, options)
 };
 
 SVGCanvasElement.prototype.addEventListener = function() {

image.js

@@ -0,0 +1,86 @@
+class ImageUtils {
+
+    /**
+     * Convert svg dataurl to canvas element
+     * 
+     * @private
+     */
+    async svg2canvas(svgDataURL, width, height) {
+        const svgImage = await new Promise((resolve) => {
+            var svgImage = new Image();
+            svgImage.onload = function() {
+                resolve(svgImage);
+            }
+            svgImage.src = svgDataURL;
+        })
+        var canvas = document.createElement('canvas');
+        canvas.width = width;
+        canvas.height = height;
+        const ctx = canvas.getContext('2d');
+        ctx.drawImage(svgImage, 0, 0);
+        return canvas;
+    }
+    
+    toDataURL(svgNode, width, height, type, encoderOptions, options) {
+        var xml = new XMLSerializer().serializeToString(svgNode);
+    
+        // documentMode is an IE-only property
+        // http://msdn.microsoft.com/en-us/library/ie/cc196988(v=vs.85).aspx
+        // http://stackoverflow.com/questions/10964966/detect-ie-version-prior-to-v9-in-javascript
+        var isIE = document.documentMode;
+    
+        if (isIE) {
+            // This is patch from canvas2svg
+            // IE search for a duplicate xmnls because they didn't implement setAttributeNS correctly
+            var xmlns = /xmlns="http:\/\/www\.w3\.org\/2000\/svg".+xmlns="http:\/\/www\.w3\.org\/2000\/svg/gi;
+            if(xmlns.test(xml)) {
+                xml = xml.replace('xmlns="http://www.w3.org/2000/svg','xmlns:xlink="http://www.w3.org/1999/xlink');
+            }
+        }
+
+        if (!options) {
+            options = {}
+        }
+    
+        var SVGDataURL = "data:image/svg+xml;charset=utf-8," + encodeURIComponent(xml);
+        if (type === "image/svg+xml" || !type) {
+            if (options.async) {
+                return Promise.resolve(SVGDataURL)
+            }
+            return SVGDataURL;
+        }
+        if (type === "image/jpeg" || type === "image/png") {
+            if (!options.async) {
+                throw new Error('svgcanvas: options.async must be set to true if type is image/jpeg | image/png')
+            }
+            return (async () => {
+                const canvas = await this.svg2canvas(SVGDataURL, width, height);
+                const dataUrl = canvas.toDataURL(type, encoderOptions);
+                canvas.remove();
+                return dataUrl;
+            })()
+        }
+        throw new Error('svgcanvas: Unknown type for toDataURL, please use image/jpeg | image/png | image/svg+xml.');
+    }
+
+    getImageData(svgNode, width, height, sx, sy, sw, sh, options) {
+        if (!options) {
+            options = {}
+        }
+        if (!options.async) {
+            throw new Error('svgcanvas: options.async must be set to true for getImageData')
+        }
+        const svgDataURL = this.toDataURL(svgNode, width, height, 'image/svg+xml');
+        return (async () => {
+            const canvas = await this.svg2canvas(svgDataURL, width, height);
+            const ctx = canvas.getContext('2d')
+            const imageData = ctx.getImageData(sx, sy, sw, sh);
+            canvas.remove();
+            return imageData;
+        })()
+    }
+}
+
+const utils = new ImageUtils();
+
+export default utils;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "svgcanvas",
-  "version": "2.1.0",
+  "version": "2.2.0",
   "description": "svgcanvas",
   "main": "dist/svgcanvas.js",
   "scripts": {