java – 在overriden paintComponent(…)方法中旋转图像

使用link中的方法(略微编辑以省略GraphicsConfiguration的使用,drawRenderImage(..)和更改的变量名称)：

//https://stackoverflow.com/questions/4156518/rotate-an-image-in-java
public static BufferedImage createTransformedImage(BufferedImage image,double angle) {
    double sin = Math.abs(Math.sin(angle));
    double cos = Math.abs(Math.cos(angle));
    int originalWidth = image.getWidth();
    int originalHeight = image.getHeight();
    int newWidth = (int) Math.floor(originalWidth * cos + originalHeight * sin);
    int newHeight = (int) Math.floor(originalHeight * cos + originalWidth * sin);
    BufferedImage rotatedBI = new BufferedImage(newWidth,newHeight,BufferedImage.TRANSLUCENT);
    Graphics2D g2d = rotatedBI.createGraphics();
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
    g2d.translate((newWidth - originalWidth) / 2,(newHeight - originalHeight) / 2);
    g2d.rotate(angle,originalWidth / 2,originalHeight / 2);
    g2d.drawImage(image,null);
    g2d.dispose();
    return rotatedBI;
}

这是一个例子：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class RotateImage {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new MyRotatableImage(createImage(),-45));
                frame.pack();
                frame.setVisible(true);
            }
        });
    }

    public static BufferedImage createImage() {
        BufferedImage img = new BufferedImage(100,50,BufferedImage.TRANSLUCENT);
        Graphics2D g2d = img.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setColor(Color.WHITE);
        g2d.fillRect(0,img.getWidth(),img.getHeight());
        g2d.setColor(Color.BLACK);
        g2d.setFont(new Font("Calibri",Font.BOLD,20));
        FontMetrics fm = g2d.getFontMetrics();
        String text = "Hello world";
        int textWidth = fm.stringWidth(text);
        g2d.drawString(text,(img.getWidth() / 2) - textWidth / 2,img.getHeight() / 2);
        g2d.dispose();
        return img;
    }
}

class MyRotatableImage extends JPanel {

    private BufferedImage transformedImage;

    public MyRotatableImage(BufferedImage img,int angle) {
        transformedImage = createTransformedImage(img,angle);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.drawImage(transformedImage,null);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(transformedImage.getWidth(),transformedImage.getHeight());
    }

    //https://stackoverflow.com/questions/4156518/rotate-an-image-in-java
    public static BufferedImage createTransformedImage(BufferedImage image,double angle) {
        double sin = Math.abs(Math.sin(angle));
        double cos = Math.abs(Math.cos(angle));
        int originalWidth = image.getWidth();
        int originalHeight = image.getHeight();
        int newWidth = (int) Math.floor(originalWidth * cos + originalHeight * sin);
        int newHeight = (int) Math.floor(originalHeight * cos + originalWidth * sin);
        BufferedImage rotatedBI = new BufferedImage(newWidth,BufferedImage.TRANSLUCENT);
        Graphics2D g2d = rotatedBI.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.translate((newWidth - originalWidth) / 2,(newHeight - originalHeight) / 2);
        g2d.rotate(angle,originalHeight / 2);
        g2d.drawImage(image,null);
        g2d.dispose();
        return rotatedBI;
    }
}

参考：

> Rotate an image in java