ActionScript 3 检查DisplayObjects的HitTest / Collision检测

Posted 2021-05-23

/*
Copyright (c) 2008 Tink Ltd - http://www.tink.ws

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package ws.tink.display {

	import flash.display.BitmapData;
	import flash.display.BlendMode;
	import flash.display.DisplayObject;
	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, accuracy : Number = 1 ):Boolean {
			return complexIntersectionRectangle( target1, target2, accuracy ).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, accuracy : Number = 1 ):Rectangle {
			if( accuracy <= 0 )
				throw new Error( "ArgumentError: Error #5001: Invalid value for accuracy", 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 * accuracy < 1 || hitRectangle.height * accuracy < 1 )
				return new Rectangle();

			var bitmapData : BitmapData = new BitmapData( hitRectangle.width * accuracy, hitRectangle.height * accuracy, false, 0x000000 );

			// Draw the first target.
			bitmapData.draw( target1, HitTest.getDrawMatrix( target1, hitRectangle, accuracy ), new ColorTransform( 1, 1, 1, 1, 255, -255, -255, 255 ) );
			// Overlay the second target.
			bitmapData.draw( target2, HitTest.getDrawMatrix( target2, hitRectangle, accuracy ), 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 accuracy
			if( accuracy != 1 ) {
				intersection.x /= accuracy;
				intersection.y /= accuracy;
				intersection.width /= accuracy;
				intersection.height /= accuracy;
			}

			intersection.x += hitRectangle.x;
			intersection.y += hitRectangle.y;

			return intersection;
		}


		protected static function getDrawMatrix( target : DisplayObject, hitRectangle : Rectangle, accuracy : 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( accuracy != 1 )
				matrix.scale( accuracy, accuracy );

			return matrix;
		}

	}

}