如何使用Graphics2D旋转物体 [英] How to rotate something with Graphics2D

问题描述

所以我想旋转我制作的这个矩形

So I want to rotate this Rectangle I made

public void paint (Graphics g)
    {
        super.paint(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.fillRect(10, 10, 30, 30);
        g2.rotate(Math.toRadians(45)); //I tried this but doesn't seem to work... 
    }

我该怎么做?旋转角度为45 *或200 *.

How do I do that? Rotate as in rotate in 45* angle or 200* angle.

推荐答案

旋转对象确实并不难.下面的大多数代码只是用于创建框架和面板的样板.这是一个演示，显示了注释中提到的两种方法.

It really isn't that hard to rotate objects. Most of the code below is simply boiler plate to create the frames and panels. Here is a demo that shows two methods that were mentioned in the comments.

• 左侧面板仅旋转图形上下文.imo，这是最简单的方法，但它不会更改对象.
• 右侧面板使用 AffineTransform 旋转对象.实际上，这会改变形状的内容.

• the left panel simply rotates the graphics context. This is, imo, the easiest method but it does not alter the object.
• the right panel uses the AffineTransform to rotate the object. This actually changes the contents of the shape.

如果希望将某个物体旋转到位，则必须确保一个物体正在旋转的图像中间旋转.在下面的两种情况下，它都是(125,125)或面板和矩形的中心.

If the desire is to rotate an object in place it is necessary to ensure one is rotating about the middle of the image that is under rotation. In both cases below that would be (125,125) or the center of both the panels and the rectangle.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Polygon;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.geom.AffineTransform;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.border.LineBorder;

public class RotateRectangle extends JPanel {
    
    JFrame frame = new JFrame();
    double angle = 0;
    MyPanel mypanel = new MyPanel();
    public static void main(String[] args) {
        SwingUtilities
                .invokeLater(() -> new RotateRectangle().start());
    }
    
    public void start() {
        Timer t = new Timer(0, (ae) -> {mypanel.rotateit(); frame.repaint();});
        t.setDelay(30);
        t.start();
    }
    
    public RotateRectangle() {
        frame.setLayout(new FlowLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(this);
        frame.add(mypanel);
        setBorder(new LineBorder(Color.red,2));
        mypanel.setBorder(new LineBorder(Color.red, 2));
        frame.pack();
        // center on screen
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
    
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g.create();
        
        // visually smooth the lines
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        
        g2d.setPaint(Color.BLACK);
        g2d.rotate(angle, 125,125);
        g2d.drawRect(75, 75, 100, 100);
        
// adjust the amount of rotation per timer interval
        angle += Math.PI / 200;
        g2d.dispose();
    }
    
    public Dimension getPreferredSize() {
        return new Dimension(250, 250);
    }
    
}

class MyPanel extends JPanel {
    Polygon polygon = new Polygon();
    // amount to rotate
    double angle = Math.PI / 200;
    Shape shape = polygon;
    AffineTransform af =  new AffineTransform();

    public MyPanel() {
        af.rotate(angle, 125,125);
        polygon.addPoint(75,175);
        polygon.addPoint(175,175);
        polygon.addPoint(175,75);
        polygon.addPoint(75,75);

    }
    public void rotateit() {
        
        shape = af.createTransformedShape(shape);
    
    }
    
    public void paintComponent(Graphics g) {
        if (shape == null) {
            return;
        }
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;
        
        // visually smooth the lines
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        
        g2d.setPaint(Color.BLACK);
        g2d.draw(shape);
        
    }
    
    public Dimension getPreferredSize() {
        return new Dimension(250, 250);
    }
}

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