#

API Documentation for: 0.8.1
Show: Inherited Protected Private Deprecated

# File:AlphaMapFilter.js

    /*
     * AlphaMapFilter
     * Visit http://createjs.com/ for documentation, updates and examples.
     *
     * Copyright (c) 2010 gskinner.com, inc.
     *
     * Permission is hereby granted, free of charge, to any person
     * obtaining a copy of this software and associated documentation
     * files (the "Software"), to deal in the Software without
     * restriction, including without limitation the rights to use,
     * copy, modify, merge, publish, distribute, sublicense, and/or sell
     * copies of the Software, and to permit persons to whom the
     * Software is furnished to do so, subject to the following
     * conditions:
     *
     * The above copyright notice and this permission notice shall be
     * included in all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
     * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
     * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
     * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
     * OTHER DEALINGS IN THE SOFTWARE.
     */

    /**
     * @module EaselJS
     */

    // namespace:
    //this.createjs = this.createjs || {};

    (function () {
    	"use strict";

    // constructor:
    	/**
    	 * Applies a greyscale alpha map image (or canvas) to the target, such that the alpha channel of the result will
    	 * be copied from the red channel of the map, and the RGB channels will be copied from the target.
    	 *
    	 * Generally, it is recommended that you use {{#crossLink "AlphaMaskFilter"}}{{/crossLink}}, because it has much
    	 * better performance.
    	 *
    	 * <h4>Example</h4>
    	 * This example draws a red->blue box, caches it, and then uses the cache canvas as an alpha map on a 100x100 image.
    	 *
    	 *       var box = new createjs.Shape();
    	 *       box.graphics.beginLinearGradientFill(["#ff0000", "#0000ff"], [0, 1], 0, 0, 0, 100)
    	 *       box.graphics.drawRect(0, 0, 100, 100);
    	 *       box.cache(0, 0, 100, 100);
    	 *
    	 *       var bmp = new createjs.Bitmap("path/to/image.jpg");
    	 *       bmp.filters = [
    	 *           new createjs.AlphaMapFilter(box.cacheCanvas)
    	 *       ];
    	 *       bmp.cache(0, 0, 100, 100);
    	 *       stage.addChild(bmp);
    	 *
    	 * See {{#crossLink "Filter"}}{{/crossLink}} for more information on applying filters.
    	 * @class AlphaMapFilter
    	 * @extends Filter
    	 * @constructor
    	 * @param {HTMLImageElement|HTMLCanvasElement} alphaMap The greyscale image (or canvas) to use as the alpha value for the
    	 * result. This should be exactly the same dimensions as the target.
    	 **/
    	function AlphaMapFilter(alphaMap) {

    	// public properties:
    		/**
    		 * The greyscale image (or canvas) to use as the alpha value for the result. This should be exactly the same
    		 * dimensions as the target.
    		 * @property alphaMap
    		 * @type HTMLImageElement|HTMLCanvasElement
    		 **/
    		this.alphaMap = alphaMap;

    	// private properties:
    		/**
    		 * @property _alphaMap
    		 * @protected
    		 * @type HTMLImageElement|HTMLCanvasElement
    		 **/
    		this._alphaMap = null;

    		/**
    		 * @property _mapData
    		 * @protected
    		 * @type Uint8ClampedArray
    		 **/
    		this._mapData = null;
    	}
    	var p = createjs.extend(AlphaMapFilter, createjs.Filter);

    	// TODO: deprecated
    	// p.initialize = function() {}; // searchable for devs wondering where it is. REMOVED. See docs for details.

    // public methods:
    	/** docced in super class **/
    	p.clone = function () {
    		var o = new AlphaMapFilter(this.alphaMap);
    		o._alphaMap = this._alphaMap;
    		o._mapData = this._mapData;
    		return o;
    	};

    	/** docced in super class **/
    	p.toString = function () {
    		return "[AlphaMapFilter]";
    	};

    // private methods:
    	/** docced in super class **/
    	p._applyFilter = function (imageData) {
    		if (!this.alphaMap) { return true; }
    		if (!this._prepAlphaMap()) { return false; }

    		// TODO: update to support scenarios where the target has different dimensions.
    		var data = imageData.data;
    		var map = this._mapData;
    		for(var i=0, l=data.length; i<l; i += 4) { data[i + 3] = map[i] || 0; }

    		return true;
    	};

    	/**
    	 * @method _prepAlphaMap
    	 * @protected
    	 **/
    	p._prepAlphaMap = function () {
    		if (!this.alphaMap) { return false; }
    		if (this.alphaMap == this._alphaMap && this._mapData) { return true; }

    		this._mapData = null;
    		var map = this._alphaMap = this.alphaMap;
    		var canvas = map;
    		var ctx;
    		if (map instanceof HTMLCanvasElement) {
    			ctx = canvas.getContext("2d");
    		} else {
    			canvas = createjs.createCanvas ? createjs.createCanvas() : document.createElement("canvas");
    			canvas.width = map.width;
    			canvas.height = map.height;
    			ctx = canvas.getContext("2d");
    			ctx.drawImage(map, 0, 0);
    		}

    		try {
    			var imgData = ctx.getImageData(0, 0, map.width, map.height);
    		} catch (e) {
    			//if (!this.suppressCrossDomainErrors) throw new Error("unable to access local image data: " + e);
    			return false;
    		}

    		this._mapData = imgData.data;
    		return true;
    	};

    	createjs.AlphaMapFilter = createjs.promote(AlphaMapFilter, "Filter");
    }());