AS3 高效像素检测方法（优先，矩形，交集后，再利用通道像素差值混合）

主要代码：

package{import flash.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;/** * 总结：Jave.Lin *  * 使用：交集矩形得到的像素（两显示对象的差值混合像素后）， * 判断过滤颜色为红色的都过滤掉，如果过滤结果为Rectange.Empty， * 说明没有像素交集，否则说明的像素交集， *  * @author 原贴：http://www.tink.ws/blog/as-30-hittest/ */public class HitTest{public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject,  accurracy:Number = 1 ):Boolean{return complexIntersectionRectangle( target1, target2, accurracy ).width != 0;}//先求得两显示对象是否有最外层矩形作用矩形的交集public static function intersectionRectangle( target1:DisplayObject, target2:DisplayObject ):Rectangle{// If either of the items don't have a reference to stage, then they are not in a display list// or if a simple hitTestObject is false, they cannot be intersecting.if( !target1.root || !target2.root || !target1.hitTestObject( target2 ) ) return new Rectangle();// Get the bounds of each DisplayObject.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;}public static function complexIntersectionRectangle( target1:DisplayObject, target2:DisplayObject, accurracy:Number = 1 ):Rectangle{                     if( accurracy <= 0 ) throw new Error( "ArgumentError: Error #5001: Invalid value for accurracy", 5001 );// If a simple hitTestObject is false, they cannot be intersecting.if( !target1.hitTestObject( target2 ) ) return new Rectangle();//交集矩形得到的像素var hitRectangle:Rectangle = intersectionRectangle( target1, target2 );// If their boundaries are no interesecting, they cannot be intersecting.if( hitRectangle.width * accurracy <1 || hitRectangle.height * accurracy <1 ) return new Rectangle();var bitmapData:BitmapData = new BitmapData( hitRectangle.width * accurracy, hitRectangle.height * accurracy, false, 0x000000 ); //（两显示对象的差值混合像素后），//注意color的Offset偏移值：//第一个显示对象的将红色偏移最高，其它都最底，//第二个显示对象的将所有通道都设置为最高：255// Draw the first target.bitmapData.draw( target1, HitTest.getDrawMatrix( target1, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, -255, -255, 255 ) );// Overlay the second target.bitmapData.draw( target2, HitTest.getDrawMatrix( target2, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, 255, 255, 255 ), BlendMode.DIFFERENCE );//判断过滤颜色为红色的都过滤掉，如果过滤结果为Rectange.Empty，//说明没有像素交集，否则说明的像素交集，// Find the intersection.var intersection:Rectangle = bitmapData.getColorBoundsRect( 0xFFFFFFFF,0xFF00FFFF );bitmapData.dispose();// Alter width and positions to compensate for accurracyif( accurracy != 1 ){intersection.x /= accurracy;intersection.y /= accurracy;intersection.width /= accurracy;intersection.height /= accurracy;}//将碰撞矩形的x,y偏移到像素图像矩形的x,yintersection.x += hitRectangle.x;intersection.y += hitRectangle.y;return intersection;}//这个最要是将target只draw出hitRectangle范围的像素算法protected static function getDrawMatrix( target:DisplayObject, hitRectangle:Rectangle, accurracy:Number ):Matrix{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;}}}