[AS3] Fading Border Effect

BitmapData.copyChannel() method copies a channel from a source image and pastes it into a target image’s alpha channel. You can control the transparecy of an image by manipulating the image’s alpha channel with a source image.
The following code adds fading border effect to an image.

BitmapData.copyChannel() 메소드를 사용하여, 원하는 이미지의 특정 채널을 대상 이미지의 알파채널로 복사할 수 있습니다. 이것을 사용하면 소스 이미지를 알파채널로 사용하여 이미지의 투명도를 제어할 수 있습니다.
아래 코드는 이미지의 테두리를 부드럽게 빼는 효과를 구현한 것입니다.

/*
 * This work is licensed under a Creative Commons Attribution 3.0 License.
 * http://creativecommons.org/licenses/by/3.0/
 */

/*
 * FadeImageBorder
 * FadeImageBorder class adds the fading border effect to an image
 *
 * @author: Han Sanghun (http://hangunsworld.com/blog)
 * @last modified: 2007-05-22
 * @language version: ActionScript 3.0
 */

package{

	import	flash.display.*;
	import	flash.events.*;
	import	flash.geom.*;

	public class FadeImageBorder extends MovieClip{

		// Fade Source
		private var fade_bd:BitmapData;
		// Fade Copy
		private var fadeCopy_bd:BitmapData;

		// Original Image
		private var origin_bd:BitmapData;
		private var origin_bmp:Bitmap;
		// Result Image
		private var result_bd:BitmapData;
		private var result_bmp:Bitmap;

		/*
		 * FadeImageBorder constructor
		 */
		public function FadeImageBorder(){

			// Original image size
			var wid:uint = 400;
			var hgt:uint = 300;

			// Original/Result BitmapData
			origin_bd = new ImageSample(wid, hgt);
			result_bd = new BitmapData(wid, hgt, true, 0×00000000);
			result_bd.draw(origin_bd);

			// Fade Effect BitmapData
			fade_bd = new FadeBorderSource(500, 500);
			fadeCopy_bd = new BitmapData(wid, hgt, true, 0×00000000);

			// create fade_bmp for resizing
			var fade_bmp:Bitmap = new Bitmap(fade_bd);
			// create temporary sprite
			var fade_sp:Sprite = new Sprite();
			fade_sp.addChild(fade_bmp);
			// resize fade_bmp to fit the source image
			fade_bmp.width = wid;
			fade_bmp.height = hgt;
			// draw to fadeCopy_bd
			fadeCopy_bd.draw(fade_sp);

			// Copy alpha channel
			var rect:Rectangle = new Rectangle(0, 0, wid, hgt);
			var pnt:Point = new Point(0, 0);
			result_bd.copyChannel(fadeCopy_bd, rect, pnt, BitmapDataChannel.BLUE, BitmapDataChannel.ALPHA);

			// Add to stage
			result_bmp = new Bitmap(result_bd);
			addChild(result_bmp);
			origin_bmp = new Bitmap(origin_bd);
			addChild(origin_bmp);
			result_bmp.x = result_bmp.y = origin_bmp.x = origin_bmp.y = 25;

			// Click event
			stage.addEventListener(MouseEvent.CLICK, mouseClicked);

		}

		/*
		 * mouseClicked
		 * Add/remove the fade border effect.
		 */
		private function mouseClicked(evt:MouseEvent):void{
			origin_bmp.visible = !origin_bmp.visible;
		}

	}

}