[ActionScript 3.0] 像素级碰撞检测

 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;  

     public class HitTest
     {
         /**
          * 碰撞检测
          * @param    target1
          * @param    target2
          * @param    accurracy
          * @return
          */
         public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject,  accurracy:Number = 1 ):Boolean
         {
             return complexIntersectionRectangle( target1, target2, accurracy ).width != 0;
         }
         /**
          *
          * @param    target1
          * @param    target2
          * @return
          */
         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;
         }
         /**
          *
          * @param    target1
          * @param    target2
          * @param    accurracy
          * @return
          */
         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;
         }
         /**
          *
          * @param    target
          * @param    hitRectangle
          * @param    accurracy
          * @return
          */
         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;
         }
     }
 }