用java实现cyrus beck算法

Cyrus-Beck算法是一种线段裁剪算法，用于计算线段与裁剪窗口的交点。以下是用Java实现Cyrus-Beck算法的代码：

import java.awt.Point;

public class CyrusBeckAlgorithm {
    public static void cyrusBeckClip(Point P1, Point P2, Point winMin, Point winMax) {
        double tE = 0.0, tL = 1.0;
        double dx = P2.x - P1.x;
        double dy = P2.y - P1.y;

        double[] normal = {0, 0, 0, 0};
        normal[0] = -dy; // left edge
        normal[1] = dx; // bottom edge
        normal[2] = dy; // right edge
        normal[3] = -dx; // top edge

        double[] PE = {P1.x - winMin.x, P1.y - winMin.y, winMax.x - P1.x, winMax.y - P1.y};

        for (int i = 0; i < 4; i++) {
            double Pi = normal[i] * dx + normal[(i + 1) % 4] * dy;
            double Qi = normal[i] * PE[i] + normal[(i + 1) % 4] * PE[(i + 1) % 4];
            if (Pi == 0) {
                if (Qi < 0) {
                    System.out.println("Line outside the clip window");
                    return;
                }
            } else {
                double t = -Qi / Pi;
                if (Pi < 0) {
                    tE = Math.max(tE, t);
                } else {
                    tL = Math.min(tL, t);
                }
            }
        }

        if (tE > tL) {
            System.out.println("Line outside the clip window");
        } else {
            Point P1_clip = new Point((int) (P1.x + tE * dx), (int) (P1.y + tE * dy));
            Point P2_clip = new Point((int) (P1.x + tL * dx), (int) (P1.y + tL * dy));
            System.out.println("Line clipped from " + P1.toString() + " to " + P2.toString());
            System.out.println("Clipped line from " + P1_clip.toString() + " to " + P2_clip.toString());
        }
    }

    public static void main(String[] args) {
        Point P1 = new Point(20, 10);
        Point P2 = new Point(80, 50);
        Point winMin = new Point(30, 20);
        Point winMax = new Point(70, 40);
        cyrusBeckClip(P1, P2, winMin, winMax);
    }
}

在这个示例中，我们定义了一个线段P1P2和一个裁剪窗口Win，其中Win的上下左右边分别是(30,20)、(70,20)、(70,40)和(30,40)。算法的核心是计算线段与裁剪窗口的交点，如果存在则将线段裁剪为一个新的线段。如果不存在交点，则线段完全在裁剪窗口之外。