java - 如何实现旋转图像算法和缩放图像算法？

Question

如何实现旋转图像算法以及图像的放大或缩小？我尝试实现旋转算法，但图像没有显示，我不知道该算法是否可以，请检查旋转算法是否可以，请帮助我显示旋转后的图像并显示缩放后的图像。我想在没有预定义功能的情况下旋转和缩放图像。

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Rotation extends JPanel{

public static void main(String []args){
    JFrame f = new JFrame();
    f.add(new Rotation());
    f.setSize(750, 600);
    f.setVisible(true);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    BufferedImage img = null;
    try {
        img = ImageIO.read(new File("img.jpg"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    Rotation r = new Rotation();
    r.rotateCw(img, null);
}

public static void rotateCw( BufferedImage img, Graphics g )
{
    int         width  = img.getWidth();
    int         height = img.getHeight();
    BufferedImage   newImage = new BufferedImage( height, width, img.getType() );

    for( int i=0 ; i < width ; i++ ){
        for( int j=0 ; j < height ; j++ ){
            newImage.setRGB( height-1-j, i, img.getRGB(i,j) );;
        }
    }
    Graphics2D g2d = (Graphics2D) g;

    g2d.drawImage(newImage, 25, 25, null);
}

}

Answer 1

我只是添加另一个答案，以向您展示如何使用您在我的其他答案中询问的旋转代码。我只需更改引用 Picture 类的代码即可使用 BufferedImages。您还必须考虑新图像的大小。

public static void rotateCw( BufferedImage img, Graphics g, double degrees ) {
    int         width  = img.getWidth();
    int         height = img.getHeight();
    BufferedImage   newImage = new BufferedImage( width, height, img.getType() );

    double angle = Math.toRadians( degrees );
    double sin = Math.sin(angle);
    double cos = Math.cos(angle);
    double x0 = 0.5 * (width  - 1);     // point to rotate about
    double y0 = 0.5 * (height - 1);     // center of image

    // rotation
    for (int x = 0; x < width; x++) {
        for (int y = 0; y < height; y++) {
            double a = x - x0;
            double b = y - y0;
            int xx = (int) (+a * cos - b * sin + x0);
            int yy = (int) (+a * sin + b * cos + y0);

            if (xx >= 0 && xx < width && yy >= 0 && yy < height) {
                newImage.setRGB(x, y, img.getRGB(xx, yy));
            }
        }
    }
    Graphics2D g2d = (Graphics2D) g;
    g2d.drawImage(newImage, 0, 0, null);
}