仿射变换旋转图像

Question

我有一个名为airplane的类。在这个类中，我有变量img，它是BufferedImage类型。此外，我还有类WorldMap，它重写函数PaintComponent（Graphics g):

@Override
public void paintComponent(Graphics g) {
    Graphics2D g2d = (Graphics2D) g;
    g2d.drawImage(mapa, 0, 0, getWidth(), getHeight(), null); 
    drawAirplanes(g2d);
}

private void drawAirplane(Graphics2D g){
    for(Samolot i: s){
        i.rotateAirplane();
        g.drawImage(i.getImg(),i.getX(),i.getY(),(int)i.getDim().getWidth(),(int)i.getDim().getHeight(),  null);
    }
}

我的airplane.rotateAirplane（）函数如下所示：

 public void rotateSamolot() {
   AffineTransform tx = new AffineTransform();

   tx.translate(10,10); //10, 10 is height and width of img divide by 2
   tx.rotate(Math.PI / 2);
   tx.translate(-10,-10); 

   AffineTransformOp op = new AffineTransformOp(tx, AffineTransformOp.TYPE_BILINEAR);

   BufferedImage newImage =new BufferedImage(20, 20, img.getType()); //20, 20 is a height and width of img ofc
   op.filter(img, newImage);

       this.img = newImage;
 }

当我运行我的程序时，只绘制MAPA对象。当我删除这条车道时

this.img=newimage；

我也有我的飞机，但没有旋转。

Answer 1

主要的问题（我可以看到）是图形上下文的转换，它偏离了旋转将要发生的位置。

我“认为”旋转默认发生在graphics上下文的左上角（这里是0x0位置，您已经将其转换为其他位置），这可能会导致图像被旋转到帧外（或可视区域）

你应该提供一个旋转发生的“锚”点，通常，中心是我个人的偏好。

下面的示例仅有一个主映像（由于大小限制，我不得不缩放它，但您可能不需要它）。然后，我使用它来生成一个“旋转”实例，该实例的大小允许图像适合其中。这是一个很有趣的与trig-我从某处偷了代码，所以归功于开发人员。

该示例允许您单击任何位置，它将改变旋转枢轴，这样您就可以看到发生了什么。默认位置是窗格的中心...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
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;
import javax.swing.JSlider;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class SampleRotation {

    public static void main(String[] args) {
        new SampleRotation();
    }

    public SampleRotation() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                final RotationPane rotationPane = new RotationPane();
                final JSlider slider = new JSlider(0, 100);
                slider.addChangeListener(new ChangeListener() {
                    @Override
                    public void stateChanged(ChangeEvent e) {
                        double angle = 720d * (slider.getValue() / 100d);
                        rotationPane.setAngle(angle);
                    }
                });
                slider.setValue(0);

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(rotationPane);
                frame.add(slider, BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class RotationPane extends JPanel {

        private BufferedImage img;
        private BufferedImage rotated;
        private double angle;
        private Point clickPoint;

        public RotationPane() {
            try {
                img = ImageIO.read(new File("/Users/swhitehead/Dropbox/MegaTokyo/issue459.jpg"));
                BufferedImage scaled = new BufferedImage(img.getWidth() / 2, img.getHeight() / 2, BufferedImage.TYPE_INT_ARGB);
                Graphics2D g2d = scaled.createGraphics();
                g2d.setTransform(AffineTransform.getScaleInstance(0.5d, 0.5d));
                g2d.drawImage(img, 0, 0, this);
                g2d.dispose();
                img = scaled;
                setAngle(0d);
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            addMouseListener(new MouseAdapter() {

                @Override
                public void mouseClicked(MouseEvent e) {
                    clickPoint = e.getPoint();
                    repaint();
                }

            });

        }

        public void setAngle(double angle) {
            this.angle = angle;

            double rads = Math.toRadians(getAngle());
            double sin = Math.abs(Math.sin(rads)), cos = Math.abs(Math.cos(rads));
            int w = img.getWidth();
            int h = img.getHeight();
            int newWidth = (int) Math.floor(w * cos + h * sin);
            int newHeight = (int) Math.floor(h * cos + w * sin);

            rotated = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = rotated.createGraphics();
            AffineTransform at = new AffineTransform();
            at.translate((newWidth - w) / 2, (newHeight - h) / 2);

            int x = clickPoint == null ? w / 2 : clickPoint.x;
            int y = clickPoint == null ? h / 2 : clickPoint.y;

            at.rotate(rads, x, y);
            g2d.setTransform(at);
            g2d.drawImage(img, 0, 0, this);
            g2d.setColor(Color.RED);
            g2d.drawRect(0, 0, newWidth - 1, newHeight - 1);
            g2d.dispose();

            repaint();
        }

        public double getAngle() {
            return angle;
        }

        @Override
        public Dimension getPreferredSize() {
            return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(this), img.getHeight(this));
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (rotated != null) {
                Graphics2D g2d = (Graphics2D) g.create();

                int x = (getWidth() - rotated.getWidth()) / 2;
                int y = (getHeight() - rotated.getHeight()) / 2;
                g2d.drawImage(rotated, x, y, this);

                g2d.setColor(Color.RED);

                x = clickPoint == null ? getWidth() / 2 : clickPoint.x;
                y = clickPoint == null ? getHeight()/ 2 : clickPoint.y;

                x -= 5;
                y -= 5;

                g2d.drawOval(x, y, 10, 10);
                g2d.dispose();
            }
        }        
    }    
}