捕获/保存JPanel图像

Question

我是java新手，现在想制作一个绘制图像并通过JPanel捕获它的应用程序。我尝试了很多，但失败了。我使用的代码如下。请帮忙 提前致谢。 该程序通过拖动鼠标来绘制图像。而在文本框中键入字符提供新闻扫描

import javax.swing.SwingUtilities; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.BorderFactory; 
import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Font; 
import java.awt.Graphics; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseAdapter; 
import java.awt.image.BufferedImage; 
import java.io.File; 
import java.io.IOException; 
import java.util.logging.Level; 
import java.util.logging.Logger; 
import javax.imageio.ImageIO; 
import javax.swing.JButton; 
import javax.swing.JLabel; 
import javax.swing.JTextField; 

public class SwingPaintDemo3 { 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       createAndShowGUI(); 
      } 
     }); 
    } 

    private static void createAndShowGUI() { 

     final JFrame f = new JFrame("Swing Paint Demo"); 
     f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     f.setLayout(null); 
     f.setBounds(0,0,800,600); 
     JButton scanButton=new JButton("Scan"); 
     scanButton.setBounds(0,0,75, 40); 
     f.add(scanButton); 
     JButton eraseButton=new JButton("Erase"); 
     eraseButton.setBounds(0,50,75, 40); 
     f.add(eraseButton); 
     JLabel label1=new JLabel("Program developed by Gopakumar in connection with MCA project MCP 60"); 
     label1.setBounds(0, 500, 600,50); 
     f.add(label1); 
     final JTextField textBox=new JTextField(); 
     textBox.setBounds(510, 50,50,50); 
     f.add(textBox); 
     Font font=new Font(Font.SANS_SERIF,Font.BOLD,50); 
     textBox.setFont(font); 
     final JLabel label2=new JLabel("Please type the Character for training"); 
     label2.setBounds(505, 110, 600,50); 
     f.add(label2); 
     final MyPanel pan=new MyPanel(); 
     f.add(pan); 
     f.setVisible(true); 

     eraseButton.addActionListener(new ActionListener(){ 
     public void actionPerformed(ActionEvent e) 
     { 
     f.repaint(); 
     } 
     }); 
     scanButton.addActionListener(new ActionListener(){ 
     public void actionPerformed(ActionEvent e) 
     { 
     if(textBox.getDocument().getLength()<1){ 
      label2.setText("Please type the Character for training"); 
      label2.setForeground(Color.red); 
     } 
     else if(textBox.getDocument().getLength()>1){ 
      label2.setText("please Enter only one character"); 
     } 
     else{ 
      label2.setForeground(Color.BLACK); 
      label2.setText("Please type the Character for training"); 
      scan(pan); 


     } 
     } 
     }); 

    } 

    private static void scan(MyPanel pan1) { 
int i,j; 
pan1.bi.getGraphics(); 
pan1.paint(pan1.gd); 
// Save your screen shot with its label 
File outputfile = new File("image.jpg"); 
    try { 
     ImageIO.write(pan1.bi, "jpg", outputfile); 
    } catch (IOException ex) { 
     Logger.getLogger(SwingPaintDemo3.class.getName()).log(Level.SEVERE, null, ex); 
    } 

    } 
} 

class MyPanel extends JPanel { 

    private int x = 0; 
    private int y = 0; 
    private int ox = 0; 
    private int oy = 0; 
    private Graphics graphicsForDrawing; 
    //private boolean dragging; 
public BufferedImage bi=new BufferedImage(400,400,BufferedImage.TYPE_INT_RGB); 
public Graphics gd; 
    public MyPanel() { 
     this.gd = bi.getGraphics(); 
     this.paint(gd); 

     setBorder(BorderFactory.createLineBorder(Color.black)); 
     this.setBackground(Color.WHITE); 
     this.setBounds(100, 50,400, 400); 

     addMouseListener(new MouseAdapter() { 
      @Override 
      public void mousePressed(MouseEvent e) { 
       x = e.getX(); 
       y = e.getY(); 
       ox = x; 
       oy = y; 
      // dragging = true; 
      setUpDrawingGraphics(); 
      } 
     }); 

     addMouseMotionListener(new MouseAdapter() { 
      @Override 
      public void mouseDragged(MouseEvent e) { 
       x = e.getX(); 
       y = e.getY(); 
       graphicsForDrawing.drawLine(ox, oy, x, y); 
       gd.drawLine(ox, oy, x, y); 
       ox = x; 
       oy = y; 
      } 
     }); 
     addMouseListener(new MouseAdapter() { 
      @Override 
      public void mouseClicked(MouseEvent e){ 
       if(SwingUtilities.isRightMouseButton(e)){ 
        clear(); 
       } 
      } 

     }); 

    } 
    private void setUpDrawingGraphics() { 
     graphicsForDrawing = getGraphics(); 
     graphicsForDrawing.setColor(Color.black); 
     gd.setColor(Color.black); 
    } 

    public void clear(){ 
     repaint(); 
    } 


    public Dimension getPreferredSize() { 
     return new Dimension(400,300); 
    } 

    protected void paintComponent(Graphics g) { 
     super.paintComponent(g);  
     gd.drawImage(bi,0, 0, this); 

    } 
} 

Answer 1

我建议只在您的面板上绘制的时间绘制你的缓冲图像。

所以，你可以删除你的整个paintComponent(...)方法，改变你的鼠标拖拽监听到这一点：

addMouseMotionListener(new MouseAdapter() { 
    @Override 
    public void mouseDragged(MouseEvent e) { 
     x = e.getX(); 
     y = e.getY(); 
     Graphics g = bi.getGraphics(); 
     g.setColor(Color.green); 
     g.drawLine(ox, oy, x, y); 
     getGraphics().drawLine(ox, oy, x, y); 
     ox = x; 
     oy = y; 
    } 
}); 

，然后改变你的scan方法是：

private static void scan(MyPanel pan1) { 
    int i,j; 
    // Save your screen shot with its label 
    File outputfile = new File("image.jpg"); 
    try { 
     ImageIO.write(pan1.bi, "jpg", outputfile); 
    } catch (IOException ex) { 
     ex.printStackTrace(); 
    } 
}