[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 }