小编典典

编辑

：如果捕获当前Graphics2D绘画的变换，请当心将Graphics2D其重新用于同一窗口/面板的多个轻量级子项，因为这样变换将相对于父组件，而鼠标坐标将相对于父组件这个孩子。您需要捕获对

转换 所做的 更改 ，而不是其最终值。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;

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;

}

2020-09-08