#

API Documentation for: NEXT
Show: Inherited Protected Private Deprecated

# File:AlphaMaskFilter.js

    /*
     * AlphaMaskFilter
     * 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";

    	/**
    	 * Applies the alpha from the mask image (or canvas) to the target, such that the alpha channel of the result will
    	 * be derived from the mask, and the RGB channels will be copied from the target. This can be used, for example, to
    	 * apply an alpha mask to a display object. This can also be used to combine a JPG compressed RGB image with a PNG32
    	 * alpha mask, which can result in a much smaller file size than a single PNG32 containing ARGB.
    	 *
    	 * <b>IMPORTANT NOTE: This filter currently does not support the targetCtx, or targetX/Y parameters correctly.</b>
    	 *
    	 * <h4>Example</h4>
    	 * This example draws a gradient box, then caches it and uses the "cacheCanvas" as the alpha mask on a 100x100 image.
    	 *
    	 *      var box = new createjs.Shape();
    	 *      box.graphics.beginLinearGradientFill(["#000000", "rgba(0, 0, 0, 0)"], [0, 1], 0, 0, 100, 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.AlphaMaskFilter(box.cacheCanvas)
    	 *      ];
    	 *      bmp.cache(0, 0, 100, 100);
    	 *
    	 * See {{#crossLink "Filter"}}{{/crossLink}} for more information on applying filters.
    	 * @class AlphaMaskFilter
    	 * @extends Filter
    	 * @constructor
    	 * @param {Image} mask
    	 **/
    	var AlphaMaskFilter = function (mask) {
    		this.initialize(mask);
    	};
    	var p = AlphaMaskFilter.prototype = new createjs.Filter();

    // constructor:
    	/** @ignore */
    	p.initialize = function (mask) {
    		this.mask = mask;
    	};

    // public properties:

    	/**
    	 * The image (or canvas) to use as the mask.
    	 * @property mask
    	 * @type Image
    	 **/
    	p.mask = null;

    // public methods:

    	/**
    	 * Applies the filter to the specified context.
    	 *
    	 * <strong>IMPORTANT NOTE: This filter currently does not support the targetCtx, or targetX/Y parameters
    	 * correctly.</strong>
    	 * @method applyFilter
    	 * @param {CanvasRenderingContext2D} ctx The 2D context to use as the source.
    	 * @param {Number} x The x position to use for the source rect.
    	 * @param {Number} y The y position to use for the source rect.
    	 * @param {Number} width The width to use for the source rect.
    	 * @param {Number} height The height to use for the source rect.
    	 * @param {CanvasRenderingContext2D} [targetCtx] The 2D context to draw the result to. Defaults to the context passed to ctx.
    	 * @param {Number} [targetX] The x position to draw the result to. Defaults to the value passed to x.
    	 * @param {Number} [targetY] The y position to draw the result to. Defaults to the value passed to y.
    	 * @return {Boolean} If the filter was applied successfully.
    	 **/
    	p.applyFilter = function (ctx, x, y, width, height, targetCtx, targetX, targetY) {
    		if (!this.mask) {
    			return true;
    		}
    		targetCtx = targetCtx || ctx;
    		if (targetX == null) {
    			targetX = x;
    		}
    		if (targetY == null) {
    			targetY = y;
    		}

    		targetCtx.save();
    		if (ctx != targetCtx) {
    			// TODO: support targetCtx and targetX/Y
    			// clearRect, then draw the ctx in?
    		}

    		targetCtx.globalCompositeOperation = "destination-in";
    		targetCtx.drawImage(this.mask, targetX, targetY);
    		targetCtx.restore();
    		return true;
    	};

    	/**
    	 * Returns a clone of this object.
    	 * @method clone
    	 * @return {AlphaMaskFilter}
    	 **/
    	p.clone = function () {
    		return new AlphaMaskFilter(this.mask);
    	};

    	p.toString = function () {
    		return "[AlphaMaskFilter]";
    	};

    // private methods:

    	createjs.AlphaMaskFilter = AlphaMaskFilter;
    }());