getPixel32()

import flash.display.BitmapData;

var bmpData:BitmapData = new BitmapData(deinBild._width, deinBild._height, true, 0x00000000);
var mc:MovieClip = this.createEmptyMovieClip("mc", this.getNextHighestDepth());

mc.attachBitmap(bmpData, 1);
bmpData.draw(deinBild);

this.onMouseMove = function() {
	
	var alpha:Number = Number(bmpData.getPixel32(this._xmouse, this._ymouse) >> 24 & 0xFF/2.55);
	trace(alpha)
	
	if(this.mc.hitTest(_xmouse,_ymouse,true)){
		trace ("bild")
		bildtext.text = "Bild beruehrt"
	
	if (alpha == 0) {
		trace("Kein PNG-Farbbereich");
		alphatext.text = "ALPHA"
	} else {
		trace("PNG-Farbbereich");
		alphatext.text = "FARBE"
	}
	
	
	}else{
		bildtext.text = "ausserhalb"
		}
};