判断点是否在多边形的范围内

public class GeometryUtils {
	public final static double  EPSILON=0.00001;
	
	
	public static double getEpsilon(double maxx, double maxy,double minx, double miny, double epsilon){
		if((maxy-miny+maxx-minx)==0)return epsilon;
		return Math.abs(epsilon/(maxy-miny+maxx-minx));
	}

	// / <summary>
	// / <para>判断点是否在多边形的范围内</para>
	// / <para>返回值：值为1表示点在多边形范围内；</para>
	// / <para>值为0表示点在多边形边上；</para>
	// / <para>值为-1表示点不在多边形范围内。</para>
	// / </summary>
	// / <param name="point">点坐标，长度为2</param>
	// / <param name="polyline">多边形节点坐标，长度为2*n，其中n应大于或等于3，即至少为三角形</param>
	// / <returns>
	// / <para>返回值：值为1表示点在多边形范围内；</para>
	// / <para>值为0表示点在多边形边上；</para>
	// / <para>值为-1表示点不在多边形范围内。</para>
	// / </returns>
	public static int polygonIsContainPoint(double[] point, double[] polyline) {
		int result = -1, count = 0, pointcount = 0, tempI;
		double maxx = 0, minx = 0, maxy = 0, miny = 0;
		if (polyline != null) {
			int i;
			pointcount = polyline.length / 2;
			maxx = minx = polyline[0];
			maxy = miny = polyline[1];
			for (i = 0; i < pointcount; i++) {
				tempI = i + i;
				if (maxx < polyline[tempI])
					maxx = polyline[tempI];
				if (minx > polyline[tempI])
					minx = polyline[tempI];
				if (maxy < polyline[tempI + 1])
					maxy = polyline[tempI + 1];
				if (miny > polyline[tempI + 1])
					miny = polyline[tempI + 1];
			}
		}
		
		double epsilon = getEpsilon(maxx, maxy, minx, miny, EPSILON);
		
		if (point != null) {

			// 首先判断是否在面的外框范围内
			if (point[0] < minx || point[0] > maxx || point[1] < miny
					|| point[1] > maxy) {
				System.out.println("直接out");
				return result;
			} else {
				int i, j;
				j = pointcount - 1;
				double[] point1, point2;
				double tempValue;
				for (i = 0; i < pointcount; i++) {
					point1 = new double[2];
					point2 = new double[2];
					tempI = i + i;
					point1[0] = polyline[tempI];
					point1[1] = polyline[tempI + 1];
					tempI = j + j;
					point2[0] = polyline[tempI];
					point2[1] = polyline[tempI + 1];
					if ((lt(point1[0] , point[0],epsilon) &&
							(eq(point2[0],point[0],epsilon) || gt(point2[0] , point[0],epsilon) ) )
							|| (lt(point2[0] , point[0],epsilon) &&
									(eq(point1[0],point[0],epsilon)) || gt(point1[0], point[0],epsilon)  )) {
						tempValue = point1[1] + (point[0] - point1[0])
								/ (point2[0] - point1[0])
								* (point2[1] - point1[1]);
						if (tempValue < point[1]) {
							count++;
						} else if (eq(tempValue ,point[1],epsilon)) {
							count = -1;
							break;
						}
					}
					j = i;
				}
			}
		}
		if (count == -1) {
			result = 0;// 点在线段上
		} else {
			tempI = count % 2;
			if (tempI == 0)// 为偶数
			{
				result = -1;
			} else {
				result = 1;
			}
		}
		return result;
	}
	
	public static boolean eq(double a,double b, double epsilon){		
		return Math.abs(a-b)<epsilon;
	}
	
	public static boolean gt(double a,double b, double epsilon){		
		return a-b>=epsilon;
	}
	public static boolean lt(double a,double b, double epsilon){		
		return b-a>=epsilon;
	}
	
	public static void main(String[] args){
		int result =  polygonIsContainPoint(new double[]{106.63,35.85}, new double[]{106.61502,35.84901,
                106.61605,35.85133,
                106.62112,35.85416,
                106.62635,35.85305,
                106.63725,35.85219,
                106.64867,35.84953,
                106.65021,35.84627,
                106.65202,35.84052,
                106.64472,35.84352,
                106.63991,35.84781,
                106.63399,35.84798,
                106.62807,35.84549,
                106.62258,35.84704,
                106.61674,35.84841});
       System.out.println(result);
       
       result =  polygonIsContainPoint(new double[]{106.61502,35.84901}, new double[]{106.61502,35.84901,
               106.61605,35.85133,
               106.62112,35.85416,
               106.62635,35.85305,
               106.63725,35.85219,
               106.64867,35.84953,
               106.65021,35.84627,
               106.65202,35.84052,
               106.64472,35.84352,
               106.63991,35.84781,
               106.63399,35.84798,
               106.62807,35.84549,
               106.62258,35.84704,
               106.61674,35.84841});
      System.out.println(result);
       
   	  result =  polygonIsContainPoint(new double[]{10,10}, new double[]{106.61502,35.84901,
            106.61605,35.85133,
            106.62112,35.85416,
            106.62635,35.85305,
            106.63725,35.85219,
            106.64867,35.84953,
            106.65021,35.84627,
            106.65202,35.84052,
            106.64472,35.84352,
            106.63991,35.84781,
            106.63399,35.84798,
            106.62807,35.84549,
            106.62258,35.84704,
            106.61674,35.84841});
   System.out.println(result);

	}

}

原文链接:http://peizhiinfo.iteye.com/blog/1237481