michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: const Ci = Components.interfaces;
michael@0: const Cc = Components.classes;
michael@0: const Cu = Components.utils;
michael@0: 
michael@0: Cu.import("resource://gre/modules/XPCOMUtils.jsm");
michael@0: 
michael@0: const XHTML_NS = "http://www.w3.org/1999/xhtml";
michael@0: const MAXIMUM_PIXELS = Math.pow(144, 2);
michael@0: 
michael@0: function ColorAnalyzer() {
michael@0:   // a queue of callbacks for each job we give to the worker
michael@0:   this.callbacks = [];
michael@0: 
michael@0:   this.hiddenWindowDoc = Cc["@mozilla.org/appshell/appShellService;1"].
michael@0:                          getService(Ci.nsIAppShellService).
michael@0:                          hiddenDOMWindow.document;
michael@0: 
michael@0:   this.worker = new ChromeWorker("resource://gre/modules/ColorAnalyzer_worker.js");
michael@0:   this.worker.onmessage = this.onWorkerMessage.bind(this);
michael@0:   this.worker.onerror = this.onWorkerError.bind(this);
michael@0: }
michael@0: 
michael@0: ColorAnalyzer.prototype = {
michael@0:   findRepresentativeColor: function ColorAnalyzer_frc(imageURI, callback) {
michael@0:     function cleanup() {
michael@0:       image.removeEventListener("load", loadListener);
michael@0:       image.removeEventListener("error", errorListener);
michael@0:     }
michael@0:     let image = this.hiddenWindowDoc.createElementNS(XHTML_NS, "img");
michael@0:     let loadListener = this.onImageLoad.bind(this, image, callback, cleanup);
michael@0:     let errorListener = this.onImageError.bind(this, image, callback, cleanup);
michael@0:     image.addEventListener("load", loadListener);
michael@0:     image.addEventListener("error", errorListener);
michael@0:     image.src = imageURI.spec;
michael@0:   },
michael@0: 
michael@0:   onImageLoad: function ColorAnalyzer_onImageLoad(image, callback, cleanup) {
michael@0:     if (image.naturalWidth * image.naturalHeight > MAXIMUM_PIXELS) {
michael@0:       // this will probably take too long to process - fail
michael@0:       callback.onComplete(false);
michael@0:     } else {
michael@0:       let canvas = this.hiddenWindowDoc.createElementNS(XHTML_NS, "canvas");
michael@0:       canvas.width = image.naturalWidth;
michael@0:       canvas.height = image.naturalHeight;
michael@0:       let ctx = canvas.getContext("2d");
michael@0:       ctx.drawImage(image, 0, 0);
michael@0:       this.startJob(ctx.getImageData(0, 0, canvas.width, canvas.height),
michael@0:                     callback);
michael@0:     }
michael@0:     cleanup();
michael@0:   },
michael@0: 
michael@0:   onImageError: function ColorAnalyzer_onImageError(image, callback, cleanup) {
michael@0:     Cu.reportError("ColorAnalyzer: image at " + image.src + " didn't load");
michael@0:     callback.onComplete(false);
michael@0:     cleanup();
michael@0:   },
michael@0: 
michael@0:   startJob: function ColorAnalyzer_startJob(imageData, callback) {
michael@0:     this.callbacks.push(callback);
michael@0:     this.worker.postMessage({ imageData: imageData, maxColors: 1 });
michael@0:   },
michael@0: 
michael@0:   onWorkerMessage: function ColorAnalyzer_onWorkerMessage(event) {
michael@0:     // colors can be empty on failure
michael@0:     if (event.data.colors.length < 1) {
michael@0:       this.callbacks.shift().onComplete(false);
michael@0:     } else {
michael@0:       this.callbacks.shift().onComplete(true, event.data.colors[0]);
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   onWorkerError: function ColorAnalyzer_onWorkerError(error) {
michael@0:     // this shouldn't happen, but just in case
michael@0:     error.preventDefault();
michael@0:     Cu.reportError("ColorAnalyzer worker: " + error.message);
michael@0:     this.callbacks.shift().onComplete(false);
michael@0:   },
michael@0: 
michael@0:   classID: Components.ID("{d056186c-28a0-494e-aacc-9e433772b143}"),
michael@0:   QueryInterface: XPCOMUtils.generateQI([Ci.mozIColorAnalyzer])
michael@0: };
michael@0: 
michael@0: this.NSGetFactory = XPCOMUtils.generateNSGetFactory([ColorAnalyzer]);