/*
 * 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.
	 * @return {AlphaMaskFilter}
	 **/
	p.clone = function () {
		return new AlphaMaskFilter(this.mask);
	}

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

// private methods:


	createjs.AlphaMaskFilter = AlphaMaskFilter;
}());
