反转Java Graphics2D缩放和旋转坐标

问题描述

我使用Java中的Graphics2D来缩放和旋转我绘制的图片。我现在想要能够说出当我点击图片中的某个点时原始坐标是什么。所以考虑到旋转和缩放的坐标，我想计算出原来的坐标。有没有一种简单的方法来做到这一点？

code>在绘制图片时使用，您可以使用

to将设备空间坐标转换回用户空间

编辑：如果捕获的当前变换， code>在绘画的时候，要小心 Graphics2D 被重复用于同一个窗口/面板的多个轻量级子元素，因为那么变换将相对于父元素组件，但鼠标坐标将相对于孩子。您需要捕获您对转换进行的更改，而不是其最终值。示例：

  import java.awt.BasicStroke; 
 import java.awt.Color; 
 import java.awt.Component; 
 import java.awt.Dimension; 
 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.event.MouseMotionAdapter; 
 import java.awt.geom.AffineTransform; 
 import java.awt.geom.NoninvertibleTransformException; 
 import java.awt.image.BufferedImage; 
 import java.io.IOException; 
导入java.net.MalformedURLException; 
 import java.net.URL; 
 
 import javax.imageio.ImageIO; 
 import javax.swing.Box; 
 import javax.swing.BoxLayout; 
 import javax.swing.JComponent; 
 import javax.swing.JFrame; 
 
 public class Main {
 public static void main（String [] args）throws MalformedURLException，IOException {
 JFrame frame = new JFrame（）; 
 Box box = new Box（BoxLayout.Y_AXIS）; 
 BufferedImage image = ImageIO.read（new URL（http://sstatic.net/so/img/logo.png））; 
 AffineTransform xfrm1 = AffineTransform.getScaleInstance（0.95，1.25）; 
 xfrm1.rotate（-0.3）; 
 box.add（new ImageView（image，xfrm1））; 
 AffineTransform xfrm2 = AffineTransform.getShearInstance（0.1，0.2）; 
 xfrm2.scale（1.3，0.9）; 
 box.add（新ImageView（image，xfrm2））; 
 frame.add（box）; 
 frame.pack（）; 
 frame.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）; 
 frame.setVisible（true）; 
 
 
 $ b @SuppressWarnings（serial）
 class ImageView扩展JComponent {
 @Override 
 public void paintComponent（Graphics g ）{
 Graphics2D g2d =（Graphics2D）g; 
尝试{
 paintXfrm = g2d.getTransform（）; 
 paintXfrm.invert（）; 
 g2d.translate（getWidth（）/ 2，getHeight（）/ 2）; 
 g2d.transform（xfrm）; 
 g2d.translate（image.getWidth（）* -0.5，image.getHeight（）* -0.5）; 
 paintXfrm.concatenate（g2d.getTransform（））; 
 g2d.drawImage（image，0，0，this）; 
} catch（NoninvertibleTransformException ex）{
 ex.printStackTrace（）; 
 
 
 $ b @Override 
 public Dimension getPreferredSize（）{
 return new Dimension（image.getWidth（）* 2，image.getHeight（） ）* 2）; 
} 
 
 ImageView（最终的BufferedImage图像，最终的AffineTransform xfrm）{
 this.canvas = image.createGraphics（）; 
 canvas.setColor（Color.BLACK）; 
 canvas.setStroke（new BasicStroke（3.0f））; 
 this.image = image; 
 this.xfrm = xfrm; 
 addMouseListener（new MouseAdapter（）{
 @Override 
 public void mousePressed（MouseEvent e）{
 try {
 mouseDownCoord = e.getPoint（）; 
 paintXfrm.inverseTransform（mouseDownCoord，mouseDownCoord）; 
} catch（NoninvertibleTransformException ex）{
} 
} 
 
 @Override 
 public void mouseExited（MouseEvent e）{
 mouseDownCoord = null; 
} 
}）; 
 addMouseMotionListener（new MouseMotionAdapter（）{
 @Override 
 public void mouseDragged（MouseEvent e）{
 Point p = e.getPoint（）; 
 try {
 paintXfrm.inverseTransform（p，p）; 
 if（mouseDownCoord！= null）{
 canvas.drawLine（mouseDownCoord.x，mouseDownCoord.y，px，py）; 
 for组件同级：getParent（）。getComponents（））{
 sibling.repaint（）; 
} 
} 
 mouseDownCoord = p; 
} catch（NoninvertibleTransformException ex） {
 ex.printStackTrace（）; 
} 
} 
}）; 
} 
 
私人Graphics2D画布; 
私有BufferedImage图像; 
私人AffineTransform xfrm; 
私人AffineTransform paintXfrm; 
 private Point mouseDownCoord; 
} 
  

I use Graphics2D in Java to scale and rotate the picture I draw. I now want to be able to tell what the original coordinates were when I click on a certain point in the picture. So given the rotated and scaled coordinates I want to calculate the original ones. Is there a simple way to do this?

解决方案

If you keep a copy of the AffineTransform you use when you paint the image, you can use AffineTransform.inverseTransform(Point2D ptSrc, Point2D ptDst)to transform a device space coordinate back to user space

Edit: If you capture the current transform of the Graphics2D while painting, beware of the Graphics2D being re-used for multiple lightweight children of the same window/panel, because then the transform will be relative to the parent component but the mouse coordinates will be relative to the child. You need to capture the changes you make to the transform not its final value. Example:

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
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.event.MouseMotionAdapter;
import java.awt.geom.AffineTransform;
import java.awt.geom.NoninvertibleTransformException;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JComponent;
import javax.swing.JFrame;

public class Main {
    public static void main(String[] args) throws MalformedURLException, IOException {
        JFrame frame = new JFrame();
        Box box = new Box(BoxLayout.Y_AXIS);
        BufferedImage image = ImageIO.read(new URL("http://sstatic.net/so/img/logo.png"));
        AffineTransform xfrm1 = AffineTransform.getScaleInstance(0.95, 1.25);
        xfrm1.rotate(-0.3);
        box.add(new ImageView(image, xfrm1));
        AffineTransform xfrm2 = AffineTransform.getShearInstance(0.1, 0.2);
        xfrm2.scale(1.3, 0.9);
        box.add(new ImageView(image, xfrm2));
        frame.add(box);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

@SuppressWarnings("serial")
class ImageView extends JComponent {
    @Override
    public void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        try {
            paintXfrm = g2d.getTransform();
            paintXfrm.invert();
            g2d.translate(getWidth() / 2, getHeight() / 2);
            g2d.transform(xfrm);
            g2d.translate(image.getWidth() * -0.5, image.getHeight() * -0.5);
            paintXfrm.concatenate(g2d.getTransform());
            g2d.drawImage(image, 0, 0, this);
        } catch (NoninvertibleTransformException ex) {
            ex.printStackTrace();
        }
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(image.getWidth() * 2, image.getHeight() * 2);
    }

    ImageView(final BufferedImage image, final AffineTransform xfrm) {
        this.canvas = image.createGraphics();
        canvas.setColor(Color.BLACK);
        canvas.setStroke(new BasicStroke(3.0f));
        this.image = image;
        this.xfrm = xfrm;
        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                try {
                    mouseDownCoord = e.getPoint();
                    paintXfrm.inverseTransform(mouseDownCoord, mouseDownCoord);
                } catch (NoninvertibleTransformException ex) {
                }
            }

            @Override
            public void mouseExited(MouseEvent e) {
                mouseDownCoord = null;
            }
        });
        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                Point p = e.getPoint();
                try {
                    paintXfrm.inverseTransform(p, p);
                    if (mouseDownCoord != null) {
                        canvas.drawLine(mouseDownCoord.x, mouseDownCoord.y, p.x, p.y);
                        for (Component sibling: getParent().getComponents()) {
                            sibling.repaint();
                        }
                    }
                    mouseDownCoord = p;
                } catch (NoninvertibleTransformException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    private Graphics2D canvas;
    private BufferedImage image;
    private AffineTransform xfrm;
    private AffineTransform paintXfrm;
    private Point mouseDownCoord;
}

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