//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
    {
        /**
        * --------------------- 像素级碰撞检测
        * @param  target1    DisplayObject
        * @param  target2    DisplayObject
        * @param  accurracy  Number    检测的精度 [0 , 1]  0 <= n <= 1
        * @return        Boolean  
        */        public static function complexHitTestObject ( target1:DisplayObject, target2:DisplayObject, accurracy:Number = 1 ):Boolean
        {
            accurracy > 1 ? accurracy = 1 : 0;
            return accurracy <= 0?false:complexIntersectionRectangle(target1,target2,accurracy).width != 0;
        }

        /**
         * -------------------获取矩形边框重叠区域
         * @param  target1    DisplayObject
         * @param  target2    DisplayObject
         * @return        Rectangle
         */        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;
        }

        /**
         * -------------------------- 获取像素重叠区域
         * @param  target1    DisplayObject
         * @param  target2    DisplayObject
         * @param  accurracy  Number    精度
         * @return        Rectangle
         */        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;
        }

        /**
         * -------------------------获取MC的矩阵
         * @param  target      DisplayObject
         * @param  hitRectangle  Rectangle
         * @param  accurracy    Number
         * @return          Matrix
         */        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;
        }
    }
}