[ActionScript 3.0] 像素级碰撞检测

  1 package
  2 {
  3     import flash.display.BitmapData;
  4     import flash.display.BlendMode;
  5     import flash.display.DisplayObject;
  6     import flash.display.Sprite;
  7     import flash.geom.ColorTransform;
  8     import flash.geom.Matrix;
  9     import flash.geom.Point;
 10     import flash.geom.Rectangle;
 11
 12     public class HitTest
 13     {
 14         /**
 15          * 碰撞检测
 16          * @param    target1
 17          * @param    target2
 18          * @param    accurracy
 19          * @return
 20          */
 21         public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject,  accurracy:Number = 1 ):Boolean
 22         {
 23             return complexIntersectionRectangle( target1, target2, accurracy ).width != 0;
 24         }
 25         /**
 26          *
 27          * @param    target1
 28          * @param    target2
 29          * @return
 30          */
 31         public static function intersectionRectangle( target1:DisplayObject, target2:DisplayObject ):Rectangle
 32         {
 33             // If either of the items don‘t have a reference to stage, then they are not in a display list
 34             // or if a simple hitTestObject is false, they cannot be intersecting.
 35             if( !target1.root || !target2.root || !target1.hitTestObject( target2 ) ) return new Rectangle();
 36             // Get the bounds of each DisplayObject.
 37             var bounds1:Rectangle = target1.getBounds( target1.root );
 38             var bounds2:Rectangle = target2.getBounds( target2.root );
 39             // Determine test area boundaries.
 40             var intersection:Rectangle = new Rectangle();
 41             intersection.x   = Math.max( bounds1.x, bounds2.x );
 42             intersection.y    = Math.max( bounds1.y, bounds2.y );
 43             intersection.width      = Math.min( ( bounds1.x + bounds1.width ) - intersection.x, ( bounds2.x + bounds2.width ) - intersection.x );
 44             intersection.height = Math.min( ( bounds1.y + bounds1.height ) - intersection.y, ( bounds2.y + bounds2.height ) - intersection.y );
 45             return intersection;
 46         }
 47         /**
 48          *
 49          * @param    target1
 50          * @param    target2
 51          * @param    accurracy
 52          * @return
 53          */
 54         public static function complexIntersectionRectangle( target1:DisplayObject, target2:DisplayObject, accurracy:Number = 1 ):Rectangle
 55         {
 56             if( accurracy <= 0 ) throw new Error( "ArgumentError: Error #5001: Invalid value for accurracy", 5001 );
 57             // If a simple hitTestObject is false, they cannot be intersecting.
 58             if( !target1.hitTestObject( target2 ) ) return new Rectangle();
 59             var hitRectangle:Rectangle = intersectionRectangle( target1, target2 );
 60             // If their boundaries are no interesecting, they cannot be intersecting.
 61             if( hitRectangle.width * accurracy <1 || hitRectangle.height * accurracy <1 ) return new Rectangle();
 62             var bitmapData:BitmapData = new BitmapData( hitRectangle.width * accurracy, hitRectangle.height * accurracy, false, 0x000000 );
 63             // Draw the first target.
 64             bitmapData.draw( target1, HitTest.getDrawMatrix( target1, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, -255, -255, 255 ) );
 65             // Overlay the second target.
 66             bitmapData.draw( target2, HitTest.getDrawMatrix( target2, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, 255, 255, 255 ), BlendMode.DIFFERENCE );
 67             // Find the intersection.
 68             var intersection:Rectangle = bitmapData.getColorBoundsRect( 0xFFFFFFFF,0xFF00FFFF );
 69             bitmapData.dispose();
 70             // Alter width and positions to compensate for accurracy
 71             if( accurracy != 1 )
 72             {
 73                 intersection.x /= accurracy;
 74                 intersection.y /= accurracy;
 75                 intersection.width /= accurracy;
 76                 intersection.height /= accurracy;
 77             }
 78             intersection.x += hitRectangle.x;
 79             intersection.y += hitRectangle.y;
 80             return intersection;
 81         }
 82         /**
 83          *
 84          * @param    target
 85          * @param    hitRectangle
 86          * @param    accurracy
 87          * @return
 88          */
 89         protected static function getDrawMatrix( target:DisplayObject, hitRectangle:Rectangle, accurracy:Number ):Matrix
 90         {
 91             var localToGlobal:Point;;
 92             var matrix:Matrix;
 93             var rootConcatenatedMatrix:Matrix = target.root.transform.concatenatedMatrix;
 94             localToGlobal = target.localToGlobal( new Point( ) );
 95             matrix = target.transform.concatenatedMatrix;
 96             matrix.tx = localToGlobal.x - hitRectangle.x;
 97             matrix.ty = localToGlobal.y - hitRectangle.y;
 98             matrix.a = matrix.a / rootConcatenatedMatrix.a;
 99             matrix.d = matrix.d / rootConcatenatedMatrix.d;
100             if( accurracy != 1 ) matrix.scale( accurracy, accurracy );
101             return matrix;
102         }
103     }
104 }