Alpha mask (as3)

[ 2009-06-21 10:23:07 | Author: liuhuan ]

Font Size: Large | Medium | Small

Alpha mask is always not easy in flash, though it's so simple in other adobe produts like after effect. We can not simply make alpha mask with timeline orders. By the mergeAlpha parameter in copyPixels method, we can easily make alpha mask in actionscript 3.

Click Here to Show/Hide Media

uploads/200906/21_102624_alphamask.swf

var maskerbmp:BitmapData = new BitmapData(masker.width, masker.height, true, 0);
var picbmp:BitmapData = new BitmapData(pic.width, pic.height, true, 0);
maskerbmp.draw(masker);
picbmp.draw(pic);
var shownbmp:BitmapData = new BitmapData(pic.width, pic.height, true, 0);
var bmp:Bitmap = new Bitmap(shownbmp);
this.addChild(bmp);
this.addEventListener(Event.ENTER_FRAME, onEnterFrameHandler);
function onEnterFrameHandler(e:Event) {
  var rect1:Rectangle = new Rectangle(0, 0, masker.width, masker.height);
  var rect2:Rectangle = new Rectangle(0, 0, pic.width, pic.height);
  shownbmp.fillRect(rect2, 0);
  rect1.x = mouseX - masker.width/2;
  rect1.y = mouseY - masker.height/2;
  var pt1:Point = new Point(mouseX - masker.width/2, mouseY - masker.height/2);
  var pt2:Point = new Point(0, 0);
  shownbmp.copyPixels(picbmp, rect1, pt1,maskerbmp, pt2, true);
}

source file: