fastdetect : function(that){
 
				var half_height = this.pixels.height / 2;
				var half_width = this.pixels.width / 2;
 
				for(var y=0; y<half_height; y++){
					for(var x=0; x<half_width; x++){
						var i = (y * 8) * this.pixels.width + x * 8;
 
						var r = this.pixels.data[i];
						var g = this.pixels.data[i+1];
						var b = this.pixels.data[i+2];
 
						var tr = that.pixels.data[i];
						var tg = that.pixels.data[i+1];
						var tb = that.pixels.data[i+2];
 
						var yuv = rgb_to_yuv(r, g, b);
						var yuv2 = rgb_to_yuv(tr, tg, tb);
 
						var this_col = yuv[0];
						var that_col = yuv2[0];
 
						this_col = (((5 * this_col) + (5 * that_col))/10)-that_col;
 
						if (this_col < 0) this_col = -this_col;
 
						this_col = this_col > 15 ?  255 : 0;
 
						this.pixels.data[i] = this_col;
						this.pixels.data[i+1] = this_col;
						this.pixels.data[i+2] = this_col;
 
					}
				}
				var mask = [];
				for(var y=0; y<half_height; y++){
					for(var x=0; x<half_width; x++){
						var i = (y * 8) * this.pixels.width + x * 8;
						var erode = false;
						if (this.pixels.data[i] == 255){
							for (var yi=-2;yi<=2;yi+=2){
								for (var xi=-2;xi<=2;xi+=2){
									var px = ((y+yi) * 8) * this.pixels.width + (x+xi) * 8;
									if (this.pixels.data[px] == 0){
										erode = true;
										break;
									}
								}
							}
							mask.push({'i' : i, 'erode' : erode ? 0 : 255});
						}else {
							mask.push({'i' : i, 'erode' : 0});
						}
 
					}
				}
				for (var i=0; i<mask.length; i++){
					this.pixels.data[mask[i].i] = mask[i].erode;
					this.pixels.data[mask[i].i+1] = mask[i].erode;
					this.pixels.data[mask[i].i+2] = mask[i].erode;
				}
 
return false;
			}
 

 
	public boolean detect(byte[] data, int width, int height) {
 
 		// half width and height to reduce loops
		int half_height = height / 2;
		int half_width = width / 2;
 
		// boolean map to hold our threshold pic
		boolean[] map = new boolean[half_height * half_width];
		for (int y = 0, i = 0, ii = 0; y < half_height; y++) {
			for (int x = 0; x < half_width; x++, i+=2,ii++) {
				int l = (0xff & ((int) data[i])) - 16;
				if (previous_frame != null) {
					int pl = (0xff & ((int) previous_frame[i])) - 16;
					int d = pl;
					// merge 50% of each frame, lets not use division
					d = ((int)((5 * l) + (5 * d))-(d*10));
					// if theres a negative diff, lets reverse it
					if (d < 0){
						d = -d;
					}
					//build up our threshold map
					map[ii] = d > 150;
				}
			}
		}
		previous_frame = data;
		boolean erode = false;
		for (int y = 0, i = 0; y < half_height; y++) {
			for (int x = 0; x < half_width; x++, i++) {
				erode = false;
				if (map[i]) {
					loop through the pixels around it
					for (int yi=-2;yi<=2;yi++){
						for (int xi=-2;xi<=2;xi++){
							int px = (y+yi) * half_width + (x+xi);
							if (px >= 0 && px < map.length) {
								// if a pixel is eroded, carry on
								if (!map[px]) {
									erode = true;
									break;
								}
							}
						}
					}
					// if no pixels around this pixel have been eroded, we know there's probably some motion
					if (!erode) {
						return true;
					}
				}
			}
		}
		return false;
	}