java - 如何查看多边形中已经添加的点？

Question

Polygon polygon=new Polygon();
polygon.addPoint(6,4);
polygon.addPoint(25,4);
polygon.addPoint(25,13);
polygon.addPoint(6,13);

我需要知道点(25,4)存在于多边形中，但是

System.out.println(polygon.contains(25,4));

返回 false，这个方法看起来只是检查多边形内部的点。

那么，如何检查多边形中已添加的点？

Answer 1

假设您无法控制多边形的创建方式，您可以使用PathIterator来获取任何Polygon的每个分段。 PathIterator 包含有关每个线段的起始位置的信息:

import java.awt.*;
import java.awt.geom.*;

class PolygonUtil
{
    public static boolean contains(Polygon polygon, int x, int y)
    {
        if (polygon.contains(x, y))
            return true;

        PathIterator pi = polygon.getPathIterator(null);
        double[] location = new double[6];

        while(! pi.isDone())
        {
            int type = pi.currentSegment(location);
            int piX = (int)location[0];
            int piY = (int)location[1];

            if (x == piX && y == piY)
                return true;

            pi.next();
        }

        return false;
    }

    public static void main(String...args)
    {
        Polygon polygon=new Polygon();
        polygon.addPoint(10, 10);
        polygon.addPoint(30, 10);
        polygon.addPoint(30, 30);
        polygon.addPoint(10, 30);

        // Test 4 corners

        System.out.println("Corners:");
        System.out.println( PolygonUtil2.contains(polygon, 10, 10) );
        System.out.println( PolygonUtil2.contains(polygon, 30, 10) );
        System.out.println( PolygonUtil2.contains(polygon, 30, 30) );
        System.out.println( PolygonUtil2.contains(polygon, 10, 30) );

        // Test inside/outside left edge

        System.out.println("Left:");
        System.out.println( PolygonUtil2.contains(polygon, 9, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 10, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 11, 20) );

        // Test inside/outside left edge

        System.out.println("Right:");
        System.out.println( PolygonUtil2.contains(polygon, 29, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 30, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 31, 20) );

        // Test above/below top edge

        System.out.println("Top:");
        System.out.println( PolygonUtil2.contains(polygon, 20, 9) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 10) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 11) );

        // Test above/below bottom edge

        System.out.println("Bottom:");
        System.out.println( PolygonUtil2.contains(polygon, 20, 29) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 30) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 31) );
    }
}

或者，如果我了解在 API 中找到的 contains 方法的内部定义，您可能可以使用:

import java.awt.*;
import java.awt.geom.*;

class PolygonUtil2
{
    public static boolean contains(Polygon polygon, int x, int y)
    {
        System.out.print(x + " : " + y + " - ");

        if (polygon.contains(x, y))
            return true;

        if (polygon.contains(x - 1, y))
            return true;

        if (polygon.contains(x, y - 1))
            return true;

        if (polygon.contains(x - 1, y - 1))
            return true;

        return false;
    }

    public static void main(String...args)
    {
        Polygon polygon=new Polygon();
        polygon.addPoint(10, 10);
        polygon.addPoint(30, 10);
        polygon.addPoint(30, 30);
        polygon.addPoint(10, 30);

        // Test 4 corners

        System.out.println("Corners:");
        System.out.println( PolygonUtil2.contains(polygon, 10, 10) );
        System.out.println( PolygonUtil2.contains(polygon, 30, 10) );
        System.out.println( PolygonUtil2.contains(polygon, 30, 30) );
        System.out.println( PolygonUtil2.contains(polygon, 10, 30) );

        // Test inside/outside left edge

        System.out.println("Left:");
        System.out.println( PolygonUtil2.contains(polygon, 9, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 10, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 11, 20) );

        // Test inside/outside left edge

        System.out.println("Right:");
        System.out.println( PolygonUtil2.contains(polygon, 29, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 30, 20) );
        System.out.println( PolygonUtil2.contains(polygon, 31, 20) );

        // Test above/below top edge

        System.out.println("Top:");
        System.out.println( PolygonUtil2.contains(polygon, 20, 9) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 10) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 11) );

        // Test above/below bottom edge

        System.out.println("Bottom:");
        System.out.println( PolygonUtil2.contains(polygon, 20, 29) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 30) );
        System.out.println( PolygonUtil2.contains(polygon, 20, 31) );
    }
}

这两种方法似乎都适用于水平/垂直直线。我会让你测试有角度的线。