我有一个凸多边形(通常只是一个旋转的方形),我知道所有4个点.如何确定给定点(黄色/绿色)是否在多边形内？

编辑：对于这个特定的项目,我无法访问JDK的所有库,例如AWT.

解决方法:

此页面：http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html显示了如何为任何多边形执行此操作.

我有一个Java实现,但它太大了,不能完整地发布在这里.但是,您应该能够解决这个问题：

class Boundary {
    private final Point[] points; // Points making up the boundary
    ...


    /**
     * Return true if the given point is contained inside the boundary.
     * See: http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html
     * @param test The point to check
     * @return true if the point is inside the boundary, false otherwise
     *
     */
    public boolean contains(Point test) {
      int i;
      int j;
      boolean result = false;
      for (i = 0, j = points.length - 1; i < points.length; j = i++) {
        if ((points[i].y > test.y) != (points[j].y > test.y) &&
            (test.x < (points[j].x - points[i].x) * (test.y - points[i].y) / (points[j].y-points[i].y) + points[i].x)) {
          result = !result;
         }
      }
      return result;
    }
}

这是Point类的草图

/**
 * Two dimensional cartesian point.
 */
public class Point {
  public final double x;
  public final double y;
  ...
}