image_loader.js revision 0529e5d033099cbfc42635f6f6183833b09dff6e
1// Copyright 2013 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5'use strict'; 6 7/** 8 * Loads and resizes an image. 9 * @constructor 10 */ 11function ImageLoader() { 12 /** 13 * Persistent cache object. 14 * @type {Cache} 15 * @private 16 */ 17 this.cache_ = new Cache(); 18 19 /** 20 * Manages pending requests and runs them in order of priorities. 21 * @type {Worker} 22 * @private 23 */ 24 this.worker_ = new Worker(); 25 26 // Grant permissions to all volumes, initialize the cache and then start the 27 // worker. 28 chrome.fileBrowserPrivate.getVolumeMetadataList(function(volumeMetadataList) { 29 var initPromises = volumeMetadataList.map(function(volumeMetadata) { 30 var requestPromise = new Promise(function(callback) { 31 chrome.fileBrowserPrivate.requestFileSystem( 32 volumeMetadata.volumeId, 33 callback); 34 }); 35 return requestPromise; 36 }); 37 initPromises.push(new Promise(this.cache_.initialize.bind(this.cache_))); 38 39 // After all initializatino promises are done, start the worker. 40 Promise.all(initPromises).then(this.worker_.start.bind(this.worker_)); 41 42 // Listen for mount events, and grant permissions to volumes being mounted. 43 chrome.fileBrowserPrivate.onMountCompleted.addListener( 44 function(event) { 45 if (event.eventType == 'mount' && event.status == 'success') { 46 chrome.fileBrowserPrivate.requestFileSystem( 47 event.volumeMetadata.volumeId, function() {}); 48 } 49 }); 50 }.bind(this)); 51 52 // Listen for incoming requests. 53 chrome.extension.onMessageExternal.addListener(function(request, 54 sender, 55 sendResponse) { 56 if (ImageLoader.ALLOWED_CLIENTS.indexOf(sender.id) !== -1) { 57 // Sending a response may fail if the receiver already went offline. 58 // This is not an error, but a normal and quite common situation. 59 var failSafeSendResponse = function(response) { 60 try { 61 sendResponse(response); 62 } 63 catch (e) { 64 // Ignore the error. 65 } 66 }; 67 return this.onMessage_(sender.id, request, failSafeSendResponse); 68 } 69 }.bind(this)); 70} 71 72/** 73 * List of extensions allowed to perform image requests. 74 * 75 * @const 76 * @type {Array.<string>} 77 */ 78ImageLoader.ALLOWED_CLIENTS = 79 ['hhaomjibdihmijegdhdafkllkbggdgoj']; // File Manager's extension id. 80 81/** 82 * Handles a request. Depending on type of the request, starts or stops 83 * an image task. 84 * 85 * @param {string} senderId Sender's extension id. 86 * @param {Object} request Request message as a hash array. 87 * @param {function} callback Callback to be called to return response. 88 * @return {boolean} True if the message channel should stay alive until the 89 * callback is called. 90 * @private 91 */ 92ImageLoader.prototype.onMessage_ = function(senderId, request, callback) { 93 var requestId = senderId + ':' + request.taskId; 94 if (request.cancel) { 95 // Cancel a task. 96 this.worker_.remove(requestId); 97 return false; // No callback calls. 98 } else { 99 // Create a request task and add it to the worker (queue). 100 var requestTask = new Request(requestId, this.cache_, request, callback); 101 this.worker_.add(requestTask); 102 return true; // Request will call the callback. 103 } 104}; 105 106/** 107 * Returns the singleton instance. 108 * @return {ImageLoader} ImageLoader object. 109 */ 110ImageLoader.getInstance = function() { 111 if (!ImageLoader.instance_) 112 ImageLoader.instance_ = new ImageLoader(); 113 return ImageLoader.instance_; 114}; 115 116/** 117 * Checks if the options contain any image processing. 118 * 119 * @param {number} width Source width. 120 * @param {number} height Source height. 121 * @param {Object} options Resizing options as a hash array. 122 * @return {boolean} True if yes, false if not. 123 */ 124ImageLoader.shouldProcess = function(width, height, options) { 125 var targetDimensions = ImageLoader.resizeDimensions(width, height, options); 126 127 // Dimensions has to be adjusted. 128 if (targetDimensions.width != width || targetDimensions.height != height) 129 return true; 130 131 // Orientation has to be adjusted. 132 if (options.orientation) 133 return true; 134 135 // No changes required. 136 return false; 137}; 138 139/** 140 * Calculates dimensions taking into account resize options, such as: 141 * - scale: for scaling, 142 * - maxWidth, maxHeight: for maximum dimensions, 143 * - width, height: for exact requested size. 144 * Returns the target size as hash array with width, height properties. 145 * 146 * @param {number} width Source width. 147 * @param {number} height Source height. 148 * @param {Object} options Resizing options as a hash array. 149 * @return {Object} Dimensions, eg. {width: 100, height: 50}. 150 */ 151ImageLoader.resizeDimensions = function(width, height, options) { 152 var sourceWidth = width; 153 var sourceHeight = height; 154 155 // Flip dimensions for odd orientation values: 1 (90deg) and 3 (270deg). 156 if (options.orientation && options.orientation % 2) { 157 sourceWidth = height; 158 sourceHeight = width; 159 } 160 161 var targetWidth = sourceWidth; 162 var targetHeight = sourceHeight; 163 164 if ('scale' in options) { 165 targetWidth = sourceWidth * options.scale; 166 targetHeight = sourceHeight * options.scale; 167 } 168 169 if (options.maxWidth && 170 targetWidth > options.maxWidth) { 171 var scale = options.maxWidth / targetWidth; 172 targetWidth *= scale; 173 targetHeight *= scale; 174 } 175 176 if (options.maxHeight && 177 targetHeight > options.maxHeight) { 178 var scale = options.maxHeight / targetHeight; 179 targetWidth *= scale; 180 targetHeight *= scale; 181 } 182 183 if (options.width) 184 targetWidth = options.width; 185 186 if (options.height) 187 targetHeight = options.height; 188 189 targetWidth = Math.round(targetWidth); 190 targetHeight = Math.round(targetHeight); 191 192 return {width: targetWidth, height: targetHeight}; 193}; 194 195/** 196 * Performs resizing of the source image into the target canvas. 197 * 198 * @param {HTMLCanvasElement|Image} source Source image or canvas. 199 * @param {HTMLCanvasElement} target Target canvas. 200 * @param {Object} options Resizing options as a hash array. 201 */ 202ImageLoader.resize = function(source, target, options) { 203 var targetDimensions = ImageLoader.resizeDimensions( 204 source.width, source.height, options); 205 206 target.width = targetDimensions.width; 207 target.height = targetDimensions.height; 208 209 // Default orientation is 0deg. 210 var orientation = options.orientation || 0; 211 212 // For odd orientation values: 1 (90deg) and 3 (270deg) flip dimensions. 213 var drawImageWidth; 214 var drawImageHeight; 215 if (orientation % 2) { 216 drawImageWidth = target.height; 217 drawImageHeight = target.width; 218 } else { 219 drawImageWidth = target.width; 220 drawImageHeight = target.height; 221 } 222 223 var targetContext = target.getContext('2d'); 224 targetContext.save(); 225 targetContext.translate(target.width / 2, target.height / 2); 226 targetContext.rotate(orientation * Math.PI / 2); 227 targetContext.drawImage( 228 source, 229 0, 0, 230 source.width, source.height, 231 -drawImageWidth / 2, -drawImageHeight / 2, 232 drawImageWidth, drawImageHeight); 233 targetContext.restore(); 234}; 235