内部剪辑与Java图形

Question

我需要使用java.awt.Graphics绘制一条线,但只应渲染位于矩形外部的线条部分.

是否可以使用图形剪辑支持或者我是否需要自己计算交叉点并剪切线？

Answer 1

您需要使用Area类.此示例将演示如何执行您所要求的操作:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Area;
import java.awt.geom.Rectangle2D;

import javax.swing.JFrame;
import javax.swing.JPanel;


public class Test extends JPanel {

    public static void main(String[] args) {
        JFrame f = new JFrame();
        Test t = new Test();
        f.getContentPane().setLayout(new BorderLayout());
        f.getContentPane().add(t,BorderLayout.CENTER);
        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }

    public Test() {
        setPreferredSize(new Dimension(300, 300));
    }

    public void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D)g.create();
        Rectangle2D rectangleNotToDrawIn = new Rectangle2D.Double(100, 100, 20, 30);
        Area outside = calculateRectOutside(rectangleNotToDrawIn);
        g2.setPaint(Color.white);
        g2.fillRect(0, 0, getWidth(), getHeight());
        g2.setPaint(Color.black);
        g2.setClip(outside);
        g2.drawLine(0, 0, getWidth(), getHeight());

    }


    private Area calculateRectOutside(Rectangle2D r) {
        Area outside = new Area(new Rectangle2D.Double(0, 0, getWidth(), getHeight()));
        outside.subtract(new Area(r));
        return outside;
    }

}