使用鼠标和图形缩放

Question

我用 Graphics G（不是 2D）在我的 JComponent 中绘制了一些曲线等。

现在我想使用鼠标的滚轮来放大和缩小。

任何曲目？

我听说过 BufferredImage ？

Answer 1

我放了这个简单的代码来向你展示如何通过向 JPanel 添加 MouseWheelListener 来使用鼠标滚轮：

myJpanel.addMouseWheelListener(new MouseWheelListener() {               
   @Override
   public void mouseWheelMoved(MouseWheelEvent mwe) {
      jPanelMouseWheelMoved(mwe);
   }
});

实现鼠标滚轮监听器：

private void jPaneMouseWheelMoved(MouseWheelEvent mwe) {
    if(Event.ALT_MASK != 0) {
        if(mwe.getWheelRotation() > 0) {
            //here you put your code to scrool douwn or to minimize. 
            System.out.println(" minimize by "+(-1*mwe.getWheelRotation()));             
        }
        else if(mwe.getWheelRotation() < 0) {
            //here you put your code to scrool up or to maximize.
            System.out.println(" maximaze by "+(-1*mwe.getWheelRotation()));
        }           
    }        
}

您可以调整此示例以缩放或滚动您想要的内容。

Answer 2

您需要考虑一些注意事项...

最终结果将取决于您想要实现的目标。如果您使用 Graphics2D API 绘制曲线，则每次渲染组件时简单地缩放坐标可能会更简单。您需要确保比例的任何变化都反映在组件本身的首选尺寸中。

例如，您还可以将“默认”输出渲染到 BufferedImage 并简单地使用 AffineTransform 来更改用于渲染结果的缩放比例。

这个简单的使用BufferedImage并从磁盘加载图片，但基本概念是相同的。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseWheelEvent;
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.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ZoomPane {

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

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

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(new TestPane()));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img;
        private float scale = 1;

        public TestPane() {
            try {
                img = ImageIO.read(new File("/path/to/image"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            addMouseWheelListener(new MouseAdapter() {

                @Override
                public void mouseWheelMoved(MouseWheelEvent e) {
                    double delta = 0.05f * e.getPreciseWheelRotation();
                    scale += delta;
                    revalidate();
                    repaint();
                }

            });
        }

        @Override
        public Dimension getPreferredSize() {            
            Dimension size = new Dimension(200, 200);
            if (img != null) {            
                size.width = Math.round(img.getWidth() * scale);
                size.height = Math.round(img.getHeight() * scale);                
            }        
            return size;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (img != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                AffineTransform at = new AffineTransform();
                at.scale(scale, scale);
                g2d.drawImage(img, at, this);
                g2d.dispose();
            }
        }
    }

}

您还可以缩放直接传递给您的paintComponent 方法的Graphics 上下文。

这里重要的是记得在完成后重置AffineTransform，否则渲染时会传递给其他组件，不会产生预期的输出...

这个示例基本上创建了Graphics 上下文的副本，我们可以在不影响原始内容的情况下对其进行操作和处理，从而更容易处理

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.event.MouseAdapter;
import java.awt.event.MouseWheelEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.GeneralPath;
import java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ZoomPane {

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

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

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(new TestPane()));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private float scale = 1;

        public TestPane() {
            addMouseWheelListener(new MouseAdapter() {

                @Override
                public void mouseWheelMoved(MouseWheelEvent e) {
                    double delta = 0.05f * e.getPreciseWheelRotation();
                    scale += delta;
                    revalidate();
                    repaint();
                }

            });
        }

        @Override
        public Dimension getPreferredSize() {
            Dimension size = new Dimension(200, 200);
            size.width = Math.round(size.width * scale);
            size.height = Math.round(size.height * scale);
            return size;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            AffineTransform at = new AffineTransform();
            at.scale(scale, scale);
            g2d.setTransform(at);

            g2d.setColor(Color.RED);

            // This is for demonstration purposes only
            // I prefer to use getWidth and getHeight
            int width = 200;
            int height = 200;

            Path2D.Float path = new Path2D.Float();
            int seg = width / 3;
            path.moveTo(0, height / 2);
            path.curveTo(0, 0, seg, 0, seg, height / 2);
            path.curveTo(
                    seg, height, 
                    seg * 2, height, 
                    seg * 2, height / 2);
            path.curveTo(
                    seg * 2, 0, 
                    seg * 3, 0, 
                    seg * 3, height / 2);

            g2d.draw(path);


            g2d.dispose();
        }
    }
}

查看Transforming Shapes, Text and Images了解更多详情

Answer 3

试试JFreeChart; setMouseWheelEnabled() 方法，用于控制 ChartPanel 的缩放，在引用的示例 here 中进行了说明。