关于tink的碰撞检测类【1】

tink博客上的一个碰撞检测类，思路是：用flash自带的hitTestObject预判断，再基于像素重叠检测碰撞。

原文链接：http://www.tink.ws/blog/as-30-hittest

代码如下：package ws.tink.display
{
       
       importflash.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
       {
 
               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, thenthey are not in a display list
                       // or if a simple hitTestObject is false, they cannot beintersecting.
                       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 beintersecting.
                       if( !target1.hitTestObject( target2 ) ) return newRectangle();
                       
                       var hitRectangle:Rectangle = intersectionRectangle( target1,target2 );
                       // If their boundaries are no interesecting, they cannot beintersecting.
                       if( hitRectangle.width * accurracy <1 ||hitRectangle.height * accurracy <1 ) return newRectangle();
                       
                       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;
               }
 
       }
 
}

下一篇记下算法的思路。