BitmapData类的精确碰撞测试

import .display.BitmapData;
import flash.display.BlendMode;
import flash.display.DisplayObject;
import flash.display.Sprite;

import flash.geom.ColorTransform;
import flash.geom.Matrix;
import flash.geom.Point;
import flash.geom.Rectangle;

public class HitTest {
//========复杂（精确）碰撞测试
public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject, accurracy:Number = 1 ):Boolean {
return complexIntersectionRectangle(target1,target2,accurracy).width != 0;
}
//========返回两目标对象重叠的区域矩形
public static function intersectionRectangle( target1:DisplayObject, target2:DisplayObject ):Rectangle {

//如果目标对象不存在，或者简单碰撞测试为否，那么就不可能重叠
if ( !target1.root || !target2.root || !target1.hitTestObject( target2 ) ) {
return new Rectangle ;
}

//获取目标的边界信息Bounds
var bounds1:Rectangle = target1.getBounds( target1.root );
var bounds2:Rectangle = target2.getBounds( target2.root );

// Determine test area boundaries.
var intersection:Rectangle = new Rectangle();
intersection.x = Math.max( bounds1.x, bounds2.x );
intersection.y = Math.max( bounds1.y, bounds2.y );
intersection.width = Math.min( ( bounds1.x + bounds1.width ) - intersection.x, ( bounds2.x + bounds2.width ) - intersection.x );
intersection.height = Math.min( ( bounds1.y + bounds1.height ) - intersection.y, ( bounds2.y + bounds2.height ) - intersection.y );

return intersection;
}
//========返回复杂重叠的区域矩形
public static function complexIntersectionRectangle( target1:DisplayObject, target2:DisplayObject, accurracy:Number = 1 ):Rectangle {
if ( accurracy throw new Error("ArgumentError: Error #5001: Invalid value for accurracy",5001);
}
//如果简单碰撞为否，那么他们没有重叠
if ( !target1.hitTestObject( target2 ) ) {
return new Rectangle ;
}

var hitRectangle:Rectangle = intersectionRectangle( target1, target2 );

if ( hitRectangle.width * accurracy return new Rectangle ;
}

var bitmapData:BitmapData = new BitmapData( hitRectangle.width * accurracy, hitRectangle.height * accurracy, false, 0x000000 );

//绘制第一个目标
bitmapData.draw( target1, HitTest.getDrawMatrix( target1, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, -255, -255, 255 ) );
//绘制第二个目标
bitmapData.draw( target2, HitTest.getDrawMatrix( target2, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, 255, 255, 255 ), BlendMode.DIFFERENCE );

//确定位图图像中完全包含指定颜色的所有像素的矩形区域,以找到重叠区域
var intersection:Rectangle = bitmapData.getColorBoundsRect( 0xFFFFFFFF,0xFF00FFFF );

bitmapData.dispose();//释放bitmapData对象的内存，返回width,height为-1

if ( accurracy != 1 ) {
intersection.x /= accurracy;
intersection.y /= accurracy;
intersection.width /= accurracy;
intersection.height /= accurracy;
}
intersection.x += hitRectangle.x;
intersection.y += hitRectangle.y;

return intersection;
}
protected static function getDrawMatrix( target:DisplayObject, hitRectangle:Rectangle, accurracy:Number ):Matrix {//返回一个转换矩阵
//accurracy精确度
var localToGlobal:Point;

var matrix:Matrix;

var rootConcatenatedMatrix:Matrix = target.root.transform.concatenatedMatrix;

localToGlobal = target.localToGlobal( new Point( ) );
matrix = target.transform.concatenatedMatrix;
matrix.tx = localToGlobal.x - hitRectangle.x;
matrix.ty = localToGlobal.y - hitRectangle.y;

matrix.a = matrix.a / rootConcatenatedMatrix.a;
matrix.d = matrix.d / rootConcatenatedMatrix.d;
if ( accurracy != 1 ) {
matrix.scale( accurracy, accurracy );
}

return matrix;
}

}

}