AS3 碰撞类

 

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 {

		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, 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;
		}

		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;
		}


		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;
		}

	}

}