java - 如何在 Java 中旋转非正方形图像？

Question

我最近看到this question关于如何在 Java 中旋转图像。我直接从那个答案复制/粘贴它。在实现时，它似乎只旋转正方形的图像(即具有相同的大小、宽度和高度)。当我尝试将它用于非正方形图像时，它似乎切断了使它成为矩形的部分，如果这有意义的话。像这样

我该如何解决/解决这个问题？

编辑:我正在使用的代码。另外，我不会有滚动条，因为这将是一个“游戏”，也不会一直全屏显示。

public class Player extends Entity { //Entity has basic values such as (float) x & y values, along with some getters and setters
   double theta;    

   Reticle reticle; //draws a reticle where the cursor was(basically just replaces java.awt.Cursor due to something not neccessary for me to get into)
   Sprite currentImage; //basically just a BufferedImage that you can apply aspect ratios to

   //constructor

   @Override
   public void tick() {
      //(this line) gets the Reticle from the main-method class and set it to this reticle object
      reticleX = reticle.getX(); //basically gets the mouse coordinates
      reticleY = reticle.getY();

      x += dX; //delta or change in X
      y += dY  //delta or change in Y

      checkCollision(); //bounds checking

      //getCentralizedX()/Y() gets the center of the currentImage
      theta = getAngle(getCentralizedX(), getCentralizedY(), reticleX, reticleY);

      currentImage = Images.rotateSprite(currentImage, theta);
    }

    @Override
    public void render(Graphics g) {
        currentImage.render(g, x, y);
        g.drawLine((int) getCentralizedX(), (int) getCentralizedY(), (int) reticleX, (int) reticleY);
    }

    public double getAngle(float startX, float startY, float goalX, float goalY) {
        double angle = Math.atan2(goalY - startY, goalX - startX);
        //if(angle < 0) { //removed this as this was the thing messing up the rotation
            //angle += 360;
        //}
    }

如果士兵的角度是 90 < 角度 < 270，那么它(基本上)是，但是，如果它的 90 > 角度 > 270，那么它会有点不稳定。这里有一些照片。错误的不是瞄准线(蓝线)的角度。

删除了所有图像，因为删除了 if(angle < 0) getAngle() 内部修复了旋转错误。现在唯一的问题是它没有原地旋转。

编辑 2:我的 SSCCE，它使用与我的游戏相同的方法，但由于某种原因出现异常。

public class RotateEx extends Canvas implements Runnable {
Player player;

public RotateEx(BufferedImage image) {
    player = new Player(image, 50, 50);
    setPreferredSize(new Dimension(600, 600));
}

public void setDegrees(int degrees) {
    player.theta = Math.toRadians(degrees);
}

public BufferedImage rotateImage(BufferedImage original, double theta) {
    double cos = Math.abs(Math.cos(theta));
    double sin = Math.abs(Math.sin(theta));
    double width = original.getWidth();
    double height = original.getHeight();
    int w = (int) (width * cos + height * sin);
    int h = (int) (width * sin + height * cos);

    BufferedImage out = new BufferedImage(w, h, original.getType());
    Graphics2D g2 = out.createGraphics();
    double x = w / 2; //the middle of the two new values 
    double y = h / 2;

    AffineTransform at = AffineTransform.getRotateInstance(theta, x, y);
    x = (w - width) / 2;
    y = (h - height) / 2;
    at.translate(x, y);
    g2.drawRenderedImage(original, at);
    g2.dispose();

    return out;
}

public void tick() {
    player.tick();
}

public void render() {
    BufferStrategy bs = this.getBufferStrategy();
    if(bs == null) {
        createBufferStrategy(4);
        return;
    }

    Graphics g = bs.getDrawGraphics();
    g.setColor(Color.WHITE);
    g.fillRect(0, 0, getWidth(), getHeight());
    player.render(g);

    g.dispose();
    bs.show();
}

public static void main(String args[]) throws IOException, InterruptedException {
    String loc = "FILELOCATION"; //of course this would be a valid image file
    BufferedImage image = ImageIO.read(new File(loc));

    final RotateEx ex = new RotateEx(image);
    final JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 360, 0);
    slider.addChangeListener(new ChangeListener() {
        @Override
        public void stateChanged(ChangeEvent e) {
            int value = slider.getValue();
            ex.setDegrees(value);
        }
    });

    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.add(ex);
    f.add(slider, BorderLayout.SOUTH);
    f.pack();
    f.setLocationRelativeTo(null);
    f.setVisible(true);

    new Thread(ex).start();
}

@Override
public void run() {
    long lastTime = System.nanoTime();
    final double numTicks = 60.0;
    double n = 1000000000 / numTicks;
    double delta = 0;
    int frames = 0;
    int ticks = 0;
    long timer = System.currentTimeMillis();

    while (true) {
        long currentTime = System.nanoTime();
        delta += (currentTime - lastTime) / n;
        lastTime = currentTime;

        render();
        tick();
        frames++;

        if (delta >= 1) {
            ticks++;
            delta--;
        }
    }
}

class Player {
    public float x, y;
    int width, height;
    public double theta; //how much to rotate, in radians
    BufferedImage currentImage; //this image would change, according to the animation and what frame its on

    public Player(BufferedImage image, float x, float y) {
        this.x = x;
        this.y = y;
        width = image.getWidth();
        height = image.getHeight();
        currentImage = image;
    }

    public void tick() {
        currentImage = rotateImage(currentImage, theta);
    }

    public void render(Graphics g) {
        g.drawImage(currentImage, (int) x, (int) y, null);
    }
}

Answer 1

当您旋转图像时，宽度和高度也会发生变化，而您的代码并未考虑到这一点。

这是我手边的一些旧代码，应该可以更好地工作:

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;

public class Rotation
{
    BufferedImage image;
    JLabel label;

    public Rotation(BufferedImage image)
    {
        this.image = image;
    }

    private BufferedImage getImage(double theta)
    {
        //  Determine the size of the rotated image

        double cos = Math.abs(Math.cos(theta));
        double sin = Math.abs(Math.sin(theta));
        double width  = image.getWidth();
        double height = image.getHeight();
        int w = (int)(width * cos + height * sin);
        int h = (int)(width * sin + height * cos);

        //  Rotate and paint the original image onto a BufferedImage

        BufferedImage out = new BufferedImage(w, h, image.getType());
        Graphics2D g2 = out.createGraphics();
        g2.setPaint(UIManager.getColor("Panel.background"));
        g2.fillRect(0,0,w,h);
        double x = w/2;
        double y = h/2;
        AffineTransform at = AffineTransform.getRotateInstance(theta, x, y);
        x = (w - width)/2;
        y = (h - height)/2;
        at.translate(x, y);
        g2.drawRenderedImage(image, at);
        g2.dispose();
        return out;
    }

    private JLabel getLabel()
    {
        ImageIcon icon = new ImageIcon(image);
        label = new JLabel(icon);
        label.setHorizontalAlignment(JLabel.CENTER);
        return label;
    }

    private JSlider getSlider()
    {
        final JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 360, 0);
        slider.addChangeListener(new ChangeListener()
        {
            public void stateChanged(ChangeEvent e)
            {
                int value = slider.getValue();
                BufferedImage bi = getImage(Math.toRadians(value));
                label.setIcon(new ImageIcon(bi));
            }
        });
        return slider;
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                try
                {
                    String path = "mong.jpg";
                    ClassLoader cl = Rotation.class.getClassLoader();
                    BufferedImage bi = ImageIO.read(cl.getResourceAsStream(path));
                    Rotation r = new Rotation(bi);
                    JFrame f = new JFrame();
                    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    f.getContentPane().add(new JScrollPane(r.getLabel()));
                    f.getContentPane().add(r.getSlider(), "South");
                    f.pack();
                    f.setLocation(200,200);
                    f.setVisible(true);
                }
                catch(IOException e)
                {
                    System.out.println(e);
                }
            }
        });
    }
}

编辑:

另一种选择是创建一个图标，然后您可以使用 Rotated Icon .然后你可以在你的绘画代码中旋转和绘画图标。像这样的东西:

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;

public class Rotation3 extends JPanel
{
    private Icon icon;
    private Icon rotated;
    private int degrees;

    public Rotation3(BufferedImage image)
    {
        icon = new ImageIcon( image );
        setDegrees( 0 );
        setPreferredSize( new Dimension(600, 600) );
    }

    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        double radians = Math.toRadians( degrees );
        rotated = new RotatedIcon(icon, degrees);

        // translate x/y so Icon is rotated around a specific point (300, 300)

        int x = 300 - (rotated.getIconWidth() / 2);
        int y = 300 - (rotated.getIconHeight() / 2);
        rotated.paintIcon(this, g, x, y);

        g.setColor(Color.RED);
        g.fillOval(295, 295, 10, 10);
    }

    public void setDegrees(int degrees)
    {
        this.degrees = degrees;
        double radians = Math.toRadians( degrees );
        rotated = new RotatedIcon(icon, degrees);
        repaint();
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                try
                {
                    String path = "dukewavered.gif";
                    ClassLoader cl = Rotation3.class.getClassLoader();
                    BufferedImage bi = ImageIO.read(cl.getResourceAsStream(path));
                    final Rotation3 r = new Rotation3(bi);

                    final JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 360, 0);
                    slider.addChangeListener(new ChangeListener()
                    {
                        public void stateChanged(ChangeEvent e)
                        {
                            int value = slider.getValue();
                            r.setDegrees( value );
                        }
                    });

                    JFrame f = new JFrame();
                    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    f.add(new JScrollPane(r));
                    f.add(slider, BorderLayout.SOUTH);
                    f.pack();
                    f.setLocationRelativeTo(null);
                    f.setVisible(true);
                }
                catch(IOException e)
                {
                    System.out.println(e);
                }
            }
        });
    }
}

编辑 2:

这里有一个比我想象的更简单的例子:

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;

public class Rotation2 extends JPanel
{
    BufferedImage image;
    int degrees;
    int point = 250;

    public Rotation2(BufferedImage image)
    {
        this.image = image;
        setDegrees( 0 );
        setPreferredSize( new Dimension(600, 600) );
    }

    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        Graphics2D g2 = (Graphics2D)g.create();

        double radians = Math.toRadians( degrees );
        g2.translate(point, point);
        g2.rotate(radians);
        g2.translate(-image.getWidth(this) / 2, -image.getHeight(this) / 2);
        g2.drawImage(image, 0, 0, null);

        g2.dispose();

        g.setColor(Color.RED);
        g.fillOval(point - 5, point - 5, 10, 10);
    }

    public void setDegrees(int degrees)
    {
        this.degrees = degrees;
        repaint();
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                try
                {
//                  String path = "mong.jpg";
                    String path = "dukewavered.gif";
                    ClassLoader cl = Rotation2.class.getClassLoader();
                    BufferedImage bi = ImageIO.read(cl.getResourceAsStream(path));
                    final Rotation2 r = new Rotation2(bi);

                    final JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 360, 0);
                    slider.addChangeListener(new ChangeListener()
                    {
                        public void stateChanged(ChangeEvent e)
                        {
                            int value = slider.getValue();
                            r.setDegrees( value );
                        }
                    });

                    JFrame f = new JFrame();
                    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    f.add(new JScrollPane(r));
                    f.add(slider, BorderLayout.SOUTH);
                    f.pack();
                    f.setLocationRelativeTo(null);
                    f.setVisible(true);
                }
                catch(IOException e)
                {
                    System.out.println(e);
                }
            }
        });
    }
}

旋转代码取自:How to rotate an image gradually in Swing?