top.jfunc.common.utils.GeometryUtil Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of utils Show documentation
Show all versions of utils Show documentation
common utils like IOUtil,StrUtil,HoldProcessor.etc.
package top.jfunc.common.utils;
import java.awt.geom.Point2D;
import java.util.List;
/**
* 判断一个点是否在一个多边形内
* 提供了三种计算方式，孰好孰坏在实践中比较一下
* @author xiongshiyan at 2019/1/11 , contact me with email [email protected] or phone 15208384257
*/
public class GeometryUtil {
private static final int POLYGON_MIN_SIZE = 3;
public static boolean isPtInPolygon (Point2D.Double point , List polygon) {
assertParams(point, polygon);
int iSum,iIndex;
double dLon1 , dLon2 , dLat1 , dLat2 , dLon;
int size = polygon.size();
iSum = 0;
for (iIndex = 0; iIndex= dLat1) && (point.y < dLat2))
|| ((point.y >= dLat2) && (point.y < dLat1))) {
if (Math.abs(dLat1 - dLat2) > 0) {
//得到 A点向左射线与边的交点的x坐标：
dLon = dLon1 - ((dLon1 - dLon2) * (dLat1 - point.y) ) / (dLat1 - dLat2);
// 如果交点在A点左侧（说明是做射线与 边的交点），则射线与边的全部交点数加一：
if (dLon < point.x) {
iSum++;
}
}
}
}
return (iSum % 2) != 0;
}
/**
* 返回一个点是否在一个多边形区域内， 如果点位于多边形的顶点或边上，不算做点在多边形内，返回false
*/
public static boolean isPointInPoly(Point2D.Double point, List polygon) {
assertParams(point, polygon);
java.awt.geom.GeneralPath p = new java.awt.geom.GeneralPath();
Point2D.Double first = polygon.get(0);
p.moveTo(first.x, first.y);
int size = polygon.size();
for (int i = 1; i < size; i++) {
Point2D.Double pa = polygon.get(i);
p.lineTo(pa.x, pa.y);
}
p.lineTo(first.x, first.y);
p.closePath();
return p.contains(point);
}
/**
* 判断点是否在多边形内，如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true
* @param point 检测点
* @param polygon 多边形的顶点
* @return 点在多边形内返回true,否则返回false
*/
public static boolean isPtInPoly(Point2D.Double point, List polygon){
assertParams(point, polygon);
int N = polygon.size();
//如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true
boolean boundOrVertex = true;
//cross points count of x
int intersectCount = 0;
//浮点类型计算时候与0比较时候的容差
double precision = 2e-10;
//neighbour bound vertices
Point2D.Double p1, p2;
//当前点
Point2D.Double p = point;
//left vertex
p1 = polygon.get(0);
//check all rays
for(int i = 1; i <= N; ++i){
if(p.equals(p1)){
//p is an vertex
return boundOrVertex;
}
//right vertex
p2 = polygon.get(i % N);
//ray is outside of our interests
if(p.x < Math.min(p1.x, p2.x) || p.x > Math.max(p1.x, p2.x)){
p1 = p2;
//next ray left point
continue;
}
//ray is crossing over by the algorithm (common part of)
if(p.x > Math.min(p1.x, p2.x) && p.x < Math.max(p1.x, p2.x)){
//x is before of ray
if(p.y <= Math.max(p1.y, p2.y)){
//overlies on a horizontal ray
if(p1.x == p2.x && p.y >= Math.min(p1.y, p2.y)){
return boundOrVertex;
}
//ray is vertical
if(p1.y == p2.y){
//overlies on a vertical ray
if(p1.y == p.y){
return boundOrVertex;
//before ray
}else{
++intersectCount;
}
//cross point on the left side
}else{
//cross point of y
double xinters = (p.x - p1.x) * (p2.y - p1.y) / (p2.x - p1.x) + p1.y;
//overlies on a ray
if(Math.abs(p.y - xinters) < precision){
return boundOrVertex;
}
//before ray
if(p.y < xinters){
++intersectCount;
}
}
}
//special case when ray is crossing through the vertex
}else{
//p crossing over p2
if(p.x == p2.x && p.y <= p2.y){
//next vertex
Point2D.Double p3 = polygon.get((i+1) % N);
//p.x lies between p1.x & p3.x
if(p.x >= Math.min(p1.x, p3.x) && p.x <= Math.max(p1.x, p3.x)){
++intersectCount;
}else{
intersectCount += 2;
}
}
}
//next ray left point
p1 = p2;
}
//偶数在多边形外
if(intersectCount % 2 == 0){
return false;
//奇数在多边形内
} else {
return true;
}
}
private static void assertParams(Point2D.Double point, List polygon) {
if(null == point || null == polygon || polygon.size() < POLYGON_MIN_SIZE) {
throw new IllegalArgumentException("参数不能为空，且多边形点数大于3");
}
}
}