将 Java 2d 图形图像保存为 .png 文件

Posted 2023-02-26

【中文标题】将 Java 2d 图形图像保存为 .png 文件

【英文标题】：Saving a Java 2d graphics image as .png file

【发布时间】：2012-01-02 09:18:18

【问题描述】：

我正在绘制模拟正在生成的信息的图形表示。我有图表显示，但我遇到的问题是能够将其保存为.png。当它保存png时，文件全是黑色的，所以它不是保存我的图形而是创建一些空白的png文件。问题是我很难弄清楚如何转换为 BufferedImage 或 RenderedImage 我在 eclipse 中的所有尝试都会抛出错误，当我编译它时，它就像我上面描述的那样工作。有什么想法或建议吗？我已经坚持了几个星期，要么这是一个明显的修复，要么我无法将它保存为 png。但是根据我进行的研究，可以将 java 2d 图形 img 保存为 png 文件，我不知道我错过了什么？一双新鲜的眼睛将不胜感激！在此先感谢您，感谢您对此提出的任何建议或建议。

public class GraphDisplay extends JPanel implements RenderedImage  


    final int PAD = 20; 
    Primate p;


    public GraphDisplay()


    
    public GraphDisplay(Primate p)
        this.p = p;

    

    protected void paintComponent(Graphics g) 


        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        // now we can get x1,y1,x2,y2
        double tlx= p.getMap().getX1();
        double tly= p.getMap().getY1();
        double brx= p.getMap().getX2();
        double bry= p.getMap().getY2();


        int w = getWidth();
        int h= getHeight();

        ArrayList <Tree> t=  p.getMap().getTrees();

        ArrayList<Double> xHist = p.getXHist();
        ArrayList<Double> yHist = p.getYHist();


        ArrayList<Double> testxHist = new ArrayList();
        ArrayList<Double> testyHist = new ArrayList();
        for(double i=34;i<1000;i+=5)
        
            testxHist.add(i);
        
        for(double i=34;i<1000;i+=5)
        
            testyHist.add(i);
        


        // Draw lines.

        double scale=.45;
        g2.setBackground(Color.WHITE);
        g2.setPaint(Color.green.darker());
        for(int i = 0; i < xHist.size()-1; i++) 
            double x1 = PAD + (xHist.get(i)-tlx)*scale;
            double y1 = (tly-yHist.get(i))*scale-PAD;
            double x2 = PAD + (xHist.get(i+1)-tlx)*scale;
            double y2 = (tly-yHist.get(i+1))*scale-PAD;
            g2.draw(new Line2D.Double(x1, y1, x2, y2));
        
        // Mark path points


        if(p.getRoute()!=null)
        
            ArrayList<Double> routeX= p.getRoute().getX();
            ArrayList<Double> routeY= p.getRoute().getY();


            g2.setPaint(Color.pink);
            for(int i = 0; i < routeX.size()-1; i++) 
                double x1 = PAD + (routeX.get(i)-tlx)*scale;
                double y1 = (tly-routeY.get(i))*scale-PAD;
                double x2 = PAD + (routeX.get(i+1)-tlx)*scale;
                double y2 = (tly-routeY.get(i+1))*scale-PAD;
                g2.draw(new Line2D.Double(x1, y1, x2, y2));
            



    
        g2.setPaint(Color.red);
        for(int i = 0; i < xHist.size(); i++) 

            double x = PAD + (xHist.get(i)-tlx)*scale;
            double y = (tly-yHist.get(i))*scale-PAD;

            g2.fill(new Ellipse2D.Double(x-.75, y-.75, 1.5, 1.5));
        
        //testing purposes
        g2.setPaint(Color.BLACK);
        for(int i=0;i<t.size();i++)
        
            double x= PAD+(t.get(i).getX()-tlx)*scale;
            double y= (tly-t.get(i).getY())*scale-PAD;
            g2.fill(new Ellipse2D.Double(x-1,y-1,2,2));
        

    


    public class GraphListener implements ActionListener
    
        public void actionPerformed(ActionEvent event)
        
            saveGraph(p);
        
    



    public void saveGraph(Primate p)
       
        ImageIcon saveIcon = new ImageIcon("save.png");
        GraphDisplay graphImg = new GraphDisplay(p);

        Object graph = new GraphDisplay(p);
        BufferedImage buffGraph = new BufferedImage(500,500, BufferedImage.TYPE_INT_RGB);
        graph = buffGraph.createGraphics();
        RenderedImage rendGraph = (RenderedImage) graphImg;

        String graphFileName = JOptionPane.showInputDialog("Please enter a name for the S1Mian graphical output file: ");

        File f;
        f = new File(graphFileName + ".png");

        //every run is unique so do not allow the user to overwrite previously saved files...
        if(!f.exists())
        
            try

                ImageIO.write(buffGraph, "png", f);
                JOptionPane.showMessageDialog(null, graphFileName + ".png has been created and saved to your directory...", "File Saved", JOptionPane.INFORMATION_MESSAGE, saveIcon);
            
            catch (IOException e)
            
                e.printStackTrace();
            


        
        else

            JOptionPane.showMessageDialog(null, graphFileName +".png already exists please use a different file name...", "File Exists", JOptionPane.INFORMATION_MESSAGE, saveIcon);

        

    



    public void createGraph(Primate p)
    

        JFrame frame = new JFrame("S1Mian Graphical Output");
        //frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  //disabled now that graphical output is integrated into GUI as when clicked shut down entire program...
        JPanel savePanel = new JPanel();
        ImageIcon saveIcon = new ImageIcon("saveIcon.png");

        JButton save = new JButton("Save");
        save.setToolTipText("Saves the S1Mian graphical output to a .png file");
        save.setIcon(saveIcon);
        GraphListener gl = new GraphListener();
        save.addActionListener(gl);


        GraphDisplay graph = new GraphDisplay(p);
        graph.setPreferredSize(new Dimension(950, 900));

        JScrollPane graphScrollPane = new JScrollPane();
        graphScrollPane.setViewportView(graph);
        graphScrollPane.setViewportBorder(BorderFactory.createLineBorder(Color.black));
        frame.getContentPane().add(graphScrollPane, BorderLayout.CENTER);

        savePanel.add(save);
        frame.getContentPane().add(savePanel, BorderLayout.NORTH);

        frame.setSize(900,850);
        frame.setLocation(200,200);
        frame.setVisible(true);
    

【参考方案1】：

JPanel dPanel;
...     
public void save()

    BufferedImage bImg = new BufferedImage(dPanel.getWidth(), dPanel.getHeight(), BufferedImage.TYPE_INT_RGB);
    Graphics2D cg = bImg.createGraphics();
    dPanel.paintAll(cg);
    try 
            if (ImageIO.write(bImg, "png", new File("./output_image.png")))
            
                System.out.println("-- saved");
            
     catch (IOException e) 
            // TODO Auto-generated catch block
            e.printStackTrace();
    

【参考方案2】：

请参阅此示例：Draw an Image and save to png。

---

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.GradientPaint;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

public class WriteImageType 
  static public void main(String args[]) throws Exception 
    try 
      int width = 200, height = 200;

      // TYPE_INT_ARGB specifies the image format: 8-bit RGBA packed
      // into integer pixels
      BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);

      Graphics2D ig2 = bi.createGraphics();


      Font font = new Font("TimesRoman", Font.BOLD, 20);
      ig2.setFont(font);
      String message = "www.java2s.com!";
      FontMetrics fontMetrics = ig2.getFontMetrics();
      int stringWidth = fontMetrics.stringWidth(message);
      int stringHeight = fontMetrics.getAscent();
      ig2.setPaint(Color.black);
      ig2.drawString(message, (width - stringWidth) / 2, height / 2 + stringHeight / 4);

      ImageIO.write(bi, "PNG", new File("c:\\yourImageName.PNG"));
      ImageIO.write(bi, "JPEG", new File("c:\\yourImageName.JPG"));
      ImageIO.write(bi, "gif", new File("c:\\yourImageName.GIF"));
      ImageIO.write(bi, "BMP", new File("c:\\yourImageName.BMP"));

     catch (IOException ie) 
      ie.printStackTrace();
    

  

【参考方案3】：

Screen Image 将创建面板的缓冲图像并将图像写入文件。

【讨论】：

感谢您提供的链接，我可以同时使用它们来使其工作，但由于图像美学，最终使用了屏幕图像。非常感谢各位，问题解决了！

【参考方案4】：

您似乎从未在 saveGraph(..) 例程中实际绘制到 BufferedImage。

创建 BufferedImage 并检索该图像的 Graphics 对象后，调用传递该图形上下文的主类的 paintComponent 方法。您还创建了两个 GraphDisplay 对象，但从不使用任何一个。

    GraphDisplay graphImg = new GraphDisplay(p);

   //You don't need this one, you created one above named graphImg
   // Object graph = new GraphDisplay(p);
    BufferedImage buffGraph = new BufferedImage(500,500, BufferedImage.TYPE_INT_RGB);

    //get the graphics context for the BufferedImage
    Graphics2D graph = buffGraph.createGraphics();

    //now tell your main class to draw the image onto the BufferedImage
    graphImg.paintComponent(graph);

此时，您的 BufferedImage 现在应该与您的面板具有相同的绘图，并且您应该能够保存内容。

【讨论】：

我实现了你的建议，但它仍然呈现黑色 .png 文件，有什么建议吗？谢谢！

这是我最初尝试实现的方法，但是，当我使用 TYPE_INT_RGB 时，我得到一个全黑的 .png，而当我使用 TYPE_INT_ARGB 时，我得到一个灰色的 png 文件，其中没有任何渲染。一定是我想念的东西......再次感谢！