判断点是否在直线上或线段上 判断线段相交 点与多边形的位置关系

package
{
	import flash.display.Sprite;
	import flash.geom.Point;
	
	public class Arr extends Sprite
	{

		private const INFINITY:Number = 1e10;
		private const ESP:Number = 1e-5;;
		private const MAX_N:int = 1000;
		private var Polygon:Array=new Array;
		
		public function Arr()
		{
			var p0:Point = new Point(120,150);
			var p1:Point = new Point(120,130);
			var p2:Point = new Point(130,130);
			var p3:Point = new Point(130,120);
			var p4:Point = new Point(120,120);
			var p5:Point = new Point(120,110);
			var p6:Point = new Point(130,110);
			var p7:Point = new Point(130,100);
			var p8:Point = new Point(150,100);
			var p9:Point = new Point(150,80);
			var p10:Point = new Point(120,80);
			var p11:Point = new Point(120,0);
			var p12:Point = new Point(100,0);
			var p13:Point = new Point(100,100);
			var p14:Point = new Point(0,100);
			var p15:Point = new Point(0, 150);
			
			var s:Sprite = new Sprite  ;
			addChild(s);
			s.graphics.lineStyle(1);
			s.graphics.moveTo(p0.x,p0.y);
			s.graphics.lineTo(p1.x,p1.y);
			s.graphics.lineTo(p2.x,p2.y);
			s.graphics.lineTo(p3.x,p3.y);
			s.graphics.lineTo(p4.x,p4.y);
			s.graphics.lineTo(p5.x,p5.y);
			s.graphics.lineTo(p6.x,p6.y);
			s.graphics.lineTo(p7.x,p7.y);
			s.graphics.lineTo(p8.x,p8.y);
			s.graphics.lineTo(p9.x,p9.y);
			s.graphics.lineTo(p10.x,p10.y);
			s.graphics.lineTo(p11.x,p11.y);
			s.graphics.lineTo(p12.x,p12.y);
			s.graphics.lineTo(p13.x,p13.y);
			s.graphics.lineTo(p14.x,p14.y);
			s.graphics.lineTo(p15.x,p15.y);
			s.graphics.lineTo(p0.x,p0.y);

			
			Polygon.push(p0);
			Polygon.push(p1);
			Polygon.push(p2);
			Polygon.push(p3);
			Polygon.push(p4);
			Polygon.push(p5);
			Polygon.push(p6);
			Polygon.push(p7);
			Polygon.push(p8);
			Polygon.push(p9);
			Polygon.push(p10);
			Polygon.push(p11);
			Polygon.push(p12);
			Polygon.push(p13);
			Polygon.push(p14);
			Polygon.push(p15);
			
			var X:int = 120;
			var Y:int = 130;
			/*var X:int = 130;
			var Y:int = 165;*/
			/*var X:int = 130;
			var Y:int = 145;*/
			/*var X:int = 120;
			var Y:int = 100;*/
			/*var X:int = 110;
			var Y:int = 100;*/
			/*var X:int = 120;
			var Y:int = 125;*/
			/*var X:int = 90;
			var Y:int = 125;*/
			//var X:int = 120;
			//var Y:int = 185;
			/*var X:int = 130;
			var Y:int = 125;*/
			/*var X:int = 120;
			var Y:int = 200;*/
			var checkpoint:Point = new Point(X, Y);
			var s1:Sprite = new Sprite  ;
			addChild(s1);
			s1.graphics.beginFill(0xff00ff,1);
			s1.graphics.drawCircle(X,Y,2);
			s1.graphics.endFill();

			var m:int = InPolygon(Polygon,checkpoint);
			trace("========="+m);
		}
		// 计算叉乘 |P0P1| × |P0P2|
		public function Multiply(p1:Point,p2:Point,p0:Point):Number
		{
			return ((p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y));
		}
		// 判断线段是否包含点point
		private function IsOnline(point:Point,line:LineSegment):Boolean
		{
			return( ( Math.abs(Multiply(line.pt1, line.pt2, point)) < ESP ) &&
			( ( point.x - line.pt1.x ) * ( point.x - line.pt2.x ) <= 0 ) &&
			( ( point.y - line.pt1.y ) * ( point.y - line.pt2.y ) <= 0 ) );
		}
		// 判断线段相交
		private  function Intersect(L1:LineSegment,L2:LineSegment):Boolean
		{
			return((Math.max(L1.pt1.x, L1.pt2.x) >= Math.min(L2.pt1.x, L2.pt2.x)) &&
			(Math.max(L2.pt1.x, L2.pt2.x) >= Math.min(L1.pt1.x, L1.pt2.x)) &&
			(Math.max(L1.pt1.y, L1.pt2.y) >= Math.min(L2.pt1.y, L2.pt2.y)) &&
			(Math.max(L2.pt1.y, L2.pt2.y) >= Math.min(L1.pt1.y, L1.pt2.y)) &&
			(Multiply(L2.pt1, L1.pt2, L1.pt1) * Multiply(L1.pt2, L2.pt2, L1.pt1) >= 0) &&
			(Multiply(L1.pt1, L2.pt2, L2.pt1) * Multiply(L2.pt2, L1.pt2, L2.pt1) >= 0)
			);
		}
　　　　//线段pp1与数组arr组成的线段是否相交
		public function segmentIntersect(arr:Array,p:Point,p1:Point):LineSegment
		{
			var n:int = arr.length;
			var line:LineSegment = new LineSegment();
		   
			line.pt1 = p;
			line.pt2 = p1;
			//排除数组最后一点和第一点组成线段i<n-1就行了
			for (var i:int = 0; i < n; i++ ) 
			{
				var side:LineSegment = new LineSegment();

				side.pt1 = arr[i];
				side.pt2 = arr[(i + 1) % n];
				
				if ( Intersect(side,line) ) 
				{
					//trace("----相交了----");
					return side;
				}
			}
			return null;
		}　　		
		/* 
		 * 射线法判断点q与多边形polygon的位置关系，
		 * 要求polygon为简单多边形，
		 * 顶点逆时针排列如果点在多边形内:返回1
		 * 如果点在多边形边上:返回0
		 * 如果点在多边形外:返回-1
		 */
		public function InPolygon(polygon:Array,point:Point):int
		{
			var n:int = polygon.length;
			var count:int = 0;
			var line:LineSegment = new LineSegment();
		   
			line.pt1 = point;
			line.pt2.y = point.y;
			line.pt2.x = - INFINITY;
			for (var i:int = 0; i < n; i++ ) 
			{
				// 得到多边形的一条边
				var side:LineSegment = new LineSegment();
				side.pt1 = polygon[i];
				side.pt2 = polygon[(i + 1) % n];
				if (IsOnline(point, side)) 
				{
					trace("在多边形上");
					return 0 ;
				}
				// 如果side平行x轴则不作考虑
				if ( Math.abs(side.pt1.y - side.pt2.y) < ESP )
				{
					continue;
				}
				if ( IsOnline(side.pt1, line) ) 
				{
					if( side.pt1.y > side.pt2.y )
					{
						count++;
					}
				} 
				else if ( IsOnline(side.pt2, line) ) 
				{
					if( side.pt2.y > side.pt1.y )
					{ 
						count++;
					}
				} 
				else if ( Intersect(line, side) ) 
				{
					count++;
				}
			}
			if ( count % 2 == 1 ) 
			{
				trace("在多边形内");
				return 1;
			}
			else 
			{
				trace("在多边形外");
				return -1;
			}
		}
	}
}

	import flash.geom.Point;
	class LineSegment
	{
    	public var pt1:Point;
    	public var pt2:Point;
    	public function LineSegment()
    	{
    		this.pt1 = new Point();
    		this.pt2 = new Point();
    	}
	}