问AS3 -检查BitmapData是否完全被其他BitmapData遮挡

EN

import flash.display.BitmapData;
import flash.display.Bitmap;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.utils.ByteArray;
import flash.geom.Rectangle;

var coveredBitmapData:BitmapData = new CoveredBitmapData();
var coveringBitmapData:BitmapData = new CoveringBitmapData();


var coveringBitmap:Bitmap = new Bitmap(coveringBitmapData, "auto", true);
var coveredBitmap:Bitmap = new Bitmap(coveredBitmapData, "auto", true);

coveredBitmap.x = Math.random() * (stage.stageWidth - coveredBitmap.width);
coveredBitmap.y = Math.random() * (stage.stageHeight - coveredBitmap.height);

stage.addChild(coveredBitmap);
stage.addChild(coveringBitmap);

stage.addEventListener(MouseEvent.MOUSE_MOVE, onMouseMovement);

function onMouseMovement(e:MouseEvent):void
{
    coveringBitmap.x = mouseX - (coveringBitmap.width * .5);
    coveringBitmap.y = mouseY - (coveringBitmap.height * .5);

    checkIfCovering(coveringBitmap, coveredBitmap);
}

function checkIfCovering(bitmapA:Bitmap, bitmapB:Bitmap):Boolean
{
    //bitmapA is the covering bitmap, bitmapB is the bitmap being overlapped

    var overlappedBitmapOrigin:Point = new Point(bitmapB.x, bitmapB.y);

    var localOverlappedBitmapOrigin:Point = bitmapA.globalToLocal(overlappedBitmapOrigin);

    var overlappingPixels:Vector.<uint> = bitmapA.bitmapData.getVector(new Rectangle(localOverlappedBitmapOrigin.x, localOverlappedBitmapOrigin.y, bitmapB.width, bitmapB.height));

    if(overlappingPixels.length == 0) {
        //This means that there is no bitmap data in the rectangle we tried to capture. So we are not at all covering the underlying bitmap.
        return false;
    }

    var i:uint = 0;
    for(i; i < overlappingPixels.length; ++i) {
        if(overlappingPixels[i] == 0) {
            return false;
        }
    }

    return true;
}

var left:Boolean = object2.x <= object1.x;
var top:Boolean = object2.y <= object1.y;
var right:Boolean = object2.x + object2.width >= object1.x + object1.width;
var bottom:Boolean = object2.y + object2.height >= object1.y + object1.height;


if(left && right && top && bottom)
{
    // Completely covered.
}