java - 将 Graphics2D 转换为图像或 BufferedImage

Question

我这里有个小问题。

我有一个小程序，用户可以在其中“绘制”。为此，我使用了 java.awt.Graphics2D。 但是，我该怎么做才能将用户绘制的图像保存为 JPEG 图像，或者至少将其转换为 BufferedImage 或其他东西？我不知道该怎么做。

谢谢。

Answer 1

让他们通过 Graphics2D 对象直接在 BufferedImage 中绘制，您可以通过 getGraphics() 获得该对象。然后使用 ImageIO.write(...) 将图像输出到您想要的任何文件类型(这是受支持的)。 ImageIO API 应该可以帮助您:ImageIO API .

您会遇到的另一个问题是，一旦绘制完成，他们应该将图像保存在哪里？在他们自己的电脑上？如果是这样并且这是一个 applet 程序，那么该 applet 将需要被“签名”以便它具有写入磁盘的权限。如果您对此不确定，请查看 Google，this article ，或者您可能希望单独为这个问题写一个新问题。

编辑 1:代码示例
例如:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;

@SuppressWarnings("serial")
public class DrawAndSaveImage extends JPanel {
   private static final int BI_WIDTH = 600;
   private static final int BI_HEIGHT = BI_WIDTH;
   private static final Color LABEL_DRAW_COLOR = new Color(180, 180, 255);
   private static final Stroke LABEL_DRAW_STROKE = new BasicStroke(1);
   private static final Stroke BIMAGE_DRAW_STROKE = new BasicStroke(4);
   private static final int COLOR_DIV = 5;
   private BufferedImage bImage = new BufferedImage(BI_WIDTH, BI_HEIGHT,
            BufferedImage.TYPE_INT_RGB);
   private List<Point> pointList = new ArrayList<Point>();
   private JLabel imageLabel;
   private List<Color> colorList = new ArrayList<Color>();
   private Random random = new Random();

   public DrawAndSaveImage() {
      Graphics2D g2d = bImage.createGraphics();
      g2d.setBackground(Color.white);
      g2d.clearRect(0, 0, BI_WIDTH, BI_HEIGHT);
      g2d.dispose();

      for (int r = 0; r < COLOR_DIV; r++) {
         for (int g = 0; g < COLOR_DIV; g++) {
            for (int b = 0; b < COLOR_DIV; b++) {
               Color c = new Color((r * 255) / COLOR_DIV,
                        (g * 255) / COLOR_DIV, (b * 255) / COLOR_DIV);
               colorList.add(c);
            }
         }
      }

      imageLabel = new JLabel(new ImageIcon(bImage)) {
         @Override
         protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            paintInLabel(g);
         }
      };
      MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
      imageLabel.addMouseListener(myMouseAdapter);
      imageLabel.addMouseMotionListener(myMouseAdapter);
      imageLabel.setBorder(BorderFactory.createEtchedBorder());

      JButton saveImageBtn = new JButton("Save Image");
      saveImageBtn.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
            saveImageActionPerformed();
         }
      });

      JButton clearImageBtn = new JButton("Clear Image");
      clearImageBtn.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
            Graphics2D g2 = bImage.createGraphics();
            g2.setBackground(Color.white);
            g2.clearRect(0, 0, BI_WIDTH, BI_HEIGHT);
            g2.dispose();
            imageLabel.repaint();
         }
      });

      JPanel btnPanel = new JPanel();
      btnPanel.add(saveImageBtn);
      btnPanel.add(clearImageBtn);

      setLayout(new BorderLayout());
      add(imageLabel, BorderLayout.CENTER);
      add(btnPanel, BorderLayout.SOUTH);
   }

   private void saveImageActionPerformed() {
      JFileChooser filechooser = new JFileChooser();
      FileNameExtensionFilter filter = new FileNameExtensionFilter(
               "JPG Images", "jpg");
      filechooser.setFileFilter(filter);
      int result = filechooser.showSaveDialog(this);
      if (result == JFileChooser.APPROVE_OPTION) {
         File saveFile = filechooser.getSelectedFile();
         try {
            ImageIO.write(bImage, "jpg", saveFile);
         } catch (IOException e) {
            e.printStackTrace();
         }
      }
   }

   private void paintInLabel(Graphics g) {
      Graphics2D g2d = (Graphics2D) g;
      g2d.setColor(LABEL_DRAW_COLOR);
      g2d.setStroke(LABEL_DRAW_STROKE);
      if (pointList.size() < 2) {
         return;
      }
      for (int i = 1; i < pointList.size(); i++) {
         int x1 = pointList.get(i - 1).x;
         int y1 = pointList.get(i - 1).y;
         int x2 = pointList.get(i).x;
         int y2 = pointList.get(i).y;
         g2d.drawLine(x1, y1, x2, y2);
      }
   }

   private class MyMouseAdapter extends MouseAdapter {

      @Override
      public void mousePressed(MouseEvent e) {
         pointList.add(e.getPoint());
         imageLabel.repaint();
      }

      @Override
      public void mouseReleased(MouseEvent e) {
         Graphics2D g2d = bImage.createGraphics();
         g2d.setColor(colorList.get(random.nextInt(colorList.size())));
         g2d.setStroke(BIMAGE_DRAW_STROKE);
         if (pointList.size() >= 2) {
            for (int i = 1; i < pointList.size(); i++) {
               int x1 = pointList.get(i - 1).x;
               int y1 = pointList.get(i - 1).y;
               int x2 = pointList.get(i).x;
               int y2 = pointList.get(i).y;
               g2d.drawLine(x1, y1, x2, y2);
            }
         }
         g2d.dispose();

         pointList.clear();
         imageLabel.repaint();
      }

      @Override
      public void mouseDragged(MouseEvent e) {
         pointList.add(e.getPoint());
         imageLabel.repaint();
      }
   }

   private static void createAndShowUI() {
      JFrame frame = new JFrame("DrawAndSaveImage");
      frame.getContentPane().add(new DrawAndSaveImage());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}