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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
'use strict';
/**
* Loads and resizes an image.
* @constructor
*/
function ImageLoader() {
/**
* Persistent cache object.
* @type {Cache}
* @private
*/
this.cache_ = new Cache();
/**
* Manages pending requests and runs them in order of priorities.
* @type {Worker}
* @private
*/
this.worker_ = new Worker();
// Grant permissions to the local file system and initialize the cache.
chrome.fileBrowserPrivate.requestFileSystem(
'compatible',
function(filesystem) {
this.cache_.initialize(function() {
this.worker_.start();
}.bind(this));
}.bind(this));
chrome.extension.onMessageExternal.addListener(function(request,
sender,
sendResponse) {
if (ImageLoader.ALLOWED_CLIENTS.indexOf(sender.id) !== -1) {
// Sending a response may fail if the receiver already went offline.
// This is not an error, but a normal and quite common situation.
var failSafeSendResponse = function(response) {
try {
sendResponse(response);
}
catch (e) {
// Ignore the error.
}
};
return this.onMessage_(sender.id, request, failSafeSendResponse);
}
}.bind(this));
}
/**
* List of extensions allowed to perform image requests.
*
* @const
* @type {Array.<string>}
*/
ImageLoader.ALLOWED_CLIENTS =
['hhaomjibdihmijegdhdafkllkbggdgoj']; // File Manager's extension id.
/**
* Handles a request. Depending on type of the request, starts or stops
* an image task.
*
* @param {string} senderId Sender's extension id.
* @param {Object} request Request message as a hash array.
* @param {function} callback Callback to be called to return response.
* @return {boolean} True if the message channel should stay alive until the
* callback is called.
* @private
*/
ImageLoader.prototype.onMessage_ = function(senderId, request, callback) {
var requestId = senderId + ':' + request.taskId;
if (request.cancel) {
// Cancel a task.
this.worker_.remove(requestId);
return false; // No callback calls.
} else {
// Create a request task and add it to the worker (queue).
var requestTask = new Request(requestId, this.cache_, request, callback);
this.worker_.add(requestTask);
return true; // Request will call the callback.
}
};
/**
* Returns the singleton instance.
* @return {ImageLoader} ImageLoader object.
*/
ImageLoader.getInstance = function() {
if (!ImageLoader.instance_)
ImageLoader.instance_ = new ImageLoader();
return ImageLoader.instance_;
};
/**
* Checks if the options contain any image processing.
*
* @param {number} width Source width.
* @param {number} height Source height.
* @param {Object} options Resizing options as a hash array.
* @return {boolean} True if yes, false if not.
*/
ImageLoader.shouldProcess = function(width, height, options) {
var targetDimensions = ImageLoader.resizeDimensions(width, height, options);
// Dimensions has to be adjusted.
if (targetDimensions.width != width || targetDimensions.height != height)
return true;
// Orientation has to be adjusted.
if (options.orientation)
return true;
// No changes required.
return false;
};
/**
* Calculates dimensions taking into account resize options, such as:
* - scale: for scaling,
* - maxWidth, maxHeight: for maximum dimensions,
* - width, height: for exact requested size.
* Returns the target size as hash array with width, height properties.
*
* @param {number} width Source width.
* @param {number} height Source height.
* @param {Object} options Resizing options as a hash array.
* @return {Object} Dimensions, eg. {width: 100, height: 50}.
*/
ImageLoader.resizeDimensions = function(width, height, options) {
var sourceWidth = width;
var sourceHeight = height;
// Flip dimensions for odd orientation values: 1 (90deg) and 3 (270deg).
if (options.orientation && options.orientation % 2) {
sourceWidth = height;
sourceHeight = width;
}
var targetWidth = sourceWidth;
var targetHeight = sourceHeight;
if ('scale' in options) {
targetWidth = sourceWidth * options.scale;
targetHeight = sourceHeight * options.scale;
}
if (options.maxWidth &&
targetWidth > options.maxWidth) {
var scale = options.maxWidth / targetWidth;
targetWidth *= scale;
targetHeight *= scale;
}
if (options.maxHeight &&
targetHeight > options.maxHeight) {
var scale = options.maxHeight / targetHeight;
targetWidth *= scale;
targetHeight *= scale;
}
if (options.width)
targetWidth = options.width;
if (options.height)
targetHeight = options.height;
targetWidth = Math.round(targetWidth);
targetHeight = Math.round(targetHeight);
return {width: targetWidth, height: targetHeight};
};
/**
* Performs resizing of the source image into the target canvas.
*
* @param {HTMLCanvasElement|Image} source Source image or canvas.
* @param {HTMLCanvasElement} target Target canvas.
* @param {Object} options Resizing options as a hash array.
*/
ImageLoader.resize = function(source, target, options) {
var targetDimensions = ImageLoader.resizeDimensions(
source.width, source.height, options);
target.width = targetDimensions.width;
target.height = targetDimensions.height;
// Default orientation is 0deg.
var orientation = options.orientation || 0;
// For odd orientation values: 1 (90deg) and 3 (270deg) flip dimensions.
var drawImageWidth;
var drawImageHeight;
if (orientation % 2) {
drawImageWidth = target.height;
drawImageHeight = target.width;
} else {
drawImageWidth = target.width;
drawImageHeight = target.height;
}
var targetContext = target.getContext('2d');
targetContext.save();
targetContext.translate(target.width / 2, target.height / 2);
targetContext.rotate(orientation * Math.PI / 2);
targetContext.drawImage(
source,
0, 0,
source.width, source.height,
-drawImageWidth / 2, -drawImageHeight / 2,
drawImageWidth, drawImageHeight);
targetContext.restore();
};
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