判断一个点是否在多边形内部的GIS工具类：PipUtil
jopen
10年前
PipUtil是用来判断一个点是否在多边形内部的，可以用于GIS开发。
public class PipUtil { /** * @author Paul Hallett 10/05/2004 GIS Developer * @return boolean true if point is outside a region, false if it is fixed * in the region * @param X,Y * The cordinates of the point being located * @param Xg,Yg * Double arrays listing the x,y pointlist of the region you are * searching in * @param ncoord * is the amount of points there are in the search region */ public boolean inPolygon(double X, double Y, double[] Xg, double[] Yg, int ncoord) { int count = 0; double Gradient, Intercept, Yintercept; double maxX, minX; int i, j; for (i = 0; i < ncoord; i++) { j = (i + 1) % ncoord; maxX = Xg[i] > Xg[j] ? Xg[i] : Xg[j]; minX = Xg[i] < Xg[j] ? Xg[i] : Xg[j]; if (X < maxX && X >= minX) { Gradient = (Yg[i] - Yg[j]) / (Xg[i] - Xg[j]); Intercept = Yg[i] - Gradient * Xg[i]; Yintercept = X * Gradient + Intercept; if (Yintercept > Y) { count++; } } } return (count % 2 == 1); } public static boolean isPointInsidePolygon(double x,double y, double[] xpoly, double[] ypoly) { int i1; boolean isInside = false; double X = x; double Y = y; for (int i = 0; i < xpoly.length - 1; i++) { i1 = (i % xpoly.length) + 1; // modulus if (ypoly[i] == ypoly[i1]) if (Y == ypoly[i]) if (!(X < xpoly[i] ^ X > xpoly[i1])) return true; // If point is on the boundary return true if (X == xpoly[i] | X == xpoly[i1]) { return true; } else { if (!(Y < ypoly[i] ^ Y >= ypoly[i1])) { /* point is within y limits */ double exp = (X - xpoly[i] - (Y - ypoly[i]) * (xpoly[i1] - xpoly[i]) / (ypoly[i1] - ypoly[i])); if (exp < 0) isInside = !isInside; else if (exp == 0) return true; // point is on boundary } } } return isInside; } public static void main(String []args){ double x = 113.678316; double y = 34.781784; double[] xp = {113.658912,113.676878,113.671632,113.659918,113.652444}; double[] yp = {34.793227,34.789373,34.780301,34.77953,34.784333}; System.out.println(isPointInsidePolygon(x,y,xp,yp)); } }