/*
 * Pixastic Lib - Brightness/Contrast filter - v0.1.0
 * Copyright (c) 2008 Jacob Seidelin, jseidelin@nihilogic.dk, http://blog.nihilogic.dk/
 * MIT License [http://www.opensource.org/licenses/mit-license.php]
 */

Pixastic.Actions.brightness = {

	process : function(params) {

		var brightness = parseInt(params.options.brightness,10) || 0;
		var contrast = parseFloat(params.options.contrast)||0;
		var legacy = !!(params.options.legacy);

		if (legacy) {
			brightness = Math.min(150,Math.max(-150,brightness));
		} else {
			var brightMul = 1 + Math.min(150,Math.max(-150,brightness)) / 150;
		}
		contrast = Math.max(0,contrast+1);

		if (Pixastic.Client.hasCanvasImageData()) {
			var data = Pixastic.prepareData(params);
			var rect = params.options.rect;
			var w = rect.width;
			var h = rect.height;
			var w4 = w*4;
			var y = h;
			do {
				var offsetY = (y-1)*w4;
				var x = w;
				do {
					var offset = offsetY + (x-1)*4;

					if (legacy) {
						var r = data[offset] + brightness;
						var g = data[offset+1] + brightness;
						var b = data[offset+2] + brightness;
					} else {
						var r = data[offset] * brightMul;
						var g = data[offset+1] * brightMul;
						var b = data[offset+2] * brightMul;
					}

					if (contrast != 1) {
						r = (r - 128) * contrast + 128;
						g = (g - 128) * contrast + 128;
						b = (b - 128) * contrast + 128;
					}

					if (r < 0 ) r = 0;
					if (g < 0 ) g = 0;
					if (b < 0 ) b = 0;
					if (r > 255 ) r = 255;
					if (g > 255 ) g = 255;
					if (b > 255 ) b = 255;

					data[offset] = r;
					data[offset+1] = g;
					data[offset+2] = b;

				} while (--x);
			} while (--y);
			return true;
		}
	},
	checkSupport : function() {
		return Pixastic.Client.hasCanvasImageData();
	}
}