ActionScript像素级碰撞检测

package com.jacobi.comm.engine
{  
    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; 
     
    public class HitTest 
    { 
        /*
            该方法返回 碰撞 true/false
        */  
        public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject,  accurracy:Number = 1 ):Boolean 
        { 
                return complexIntersectionRectangle( target1, target2, accurracy ).width != 0; 
        } 
         
        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(); 
              
             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 );  
 
             // 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 ); 
              
             // Find the intersection. 
             var intersection:Rectangle = bitmapData.getColorBoundsRect( 0xFFFFFFFF,0xFF00FFFF ); 
              
             bitmapData.dispose(); 
              
             // Alter width and positions to compensate for accurracy 
             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 
        { 
             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;
         }
     }
}