package {
	import flash.display.BitmapData;

	public class RGBHistogram {
		public function calculate(bmd:BitmapData, rgb:int):Object {
			var ret:Object = {
				eBmd: new BitmapData(bmd.width, bmd.height),
				hBmd: null
			};

			// Calculate histogram and eImg
			var histogram:Array = new Array(256);
			for (var i = 0; i < 360; i++) {
				histogram[i] = 0;
			}
			for (i = 0; i < bmd.width; i++) {
				for (var j = 0; j < bmd.height; j++) {
					var c:uint = bmd.getPixel(i, j);
					c = (c >> 8*(2 - rgb)) & 0x0000FF;
					histogram[c]++;
					c = (c << 8*(2 - rgb));
					ret.eBmd.setPixel(i, j, c);
				}
			}

			ret.hBmd = toBitmapData(histogram, bmd.width);
			return ret;
		}

		/**
		 * Returns a bitmap data of wx256 visualizing the histogram.
		 */
		function toBitmapData(histogram:Array, w:int):BitmapData {
			// Find the max so that we can normalize to the width of w
			var max:int = histogram[0];
			for (var j:int = 1; j < 256; j++) {
				if (max < histogram[j]) {
					max = histogram[j];
				}
			}

			// Visualize
			var normalizer:Number = w/max;
			var ret:BitmapData = new BitmapData(w, 256);
			for (j = 0; j < 256; j++) {
				for (var i:int = 0; i < histogram[j]*normalizer; i++) {
					ret.setPixel(i, j, 0x777777);
				}
			}
			return ret;
		}
	}
}