Im converting a image into a linear 1 bit array is this the fastest way to it?

btw Sprite.sensibleResult is a threeshold number. Like 0x505050

Code:
		public function imgToArray() {
			var c:int;
			var rx:int;
			var ry:int;
			aimage=new Array(imageSize);
			for (rx=0; rx<imageWidth; rx++) {
				bitmap.lock();
				for (ry=0; ry<imageHeight; ry++) {

					//aimage[(ry*imageWidth)+rx]= 
					if (bitmap.getPixel(rx,ry)>sprite.sensibleResult) {

						aimage[(ry*imageWidth)+rx]=true;
						//bitmap.setPixel(rx,ry,0xFFFFFF);
					} else {
						aimage[(ry*imageWidth)+rx]=false;
						//bitmap.setPixel(rx,ry,0x000000);
					}
					//trace(aimage[(ry*imageWidth)+rx]);

				}
				bitmap.unlock();
			}
		}