Search code examples
javahtmlswingjlabelbufferedimage

Render image dynamically

I'm trying to render an image from a dynamic html layout. How can I set the width and height of image dynamically based on the height and width of the table inside the html. I mean how can I find the table width(x) and height(y) from the html?

    JLabel label = new JLabel(html);
    label.setSize(x, y);
    BufferedImage image = new BufferedImage(label.getWidth(),label.getHeight(),BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2d = (Graphics2D)image.getGraphics();
    g2d.setColor(Color.WHITE);
    g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
    label.paint(g2d);
    g2d.dispose();
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try {
        ImageIO.write(image, "png", baos);
    } catch (IOException e) {
        e.printStackTrace();
    }

Below is a outline of the html.

<html>
<head>....</head>
<body topmargin="0" leftmargin="0"><table border=0 cellpadding=0 cellspacing=0 width=700 style='border-collapse:collapse;table-layout:fixed;width:684pt'>
......
......
</body></html>
Solution

  • The following code works. The idea is that, if you don't put the rendering JLabel inside a container with a LayoutManager, you will need to set the size of the JLabel yourself. The appropriate size can easily be found with getPreferredSize(). This should be done exclusively in this situation. In all other cases, you should not call setSize() yourself and you should leave all that to the LayoutManager.

    The result image:

    enter image description here

    import java.awt.Color;
import java.awt.Desktop;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

class TestPaint {

    protected void initUI() {
        StringBuilder sb = new StringBuilder("<html>");
        sb.append("<table>");
        for (int i = 0; i < 5; i++) {
            sb.append("<tr>");
            for (int j = 0; j < 5; j++) {
                sb.append("<td>");
                sb.append("Cell ").append(i + 1).append(' ').append(j + 1);
                sb.append("</td>");
            }
            sb.append("</tr>");
        }
        sb.append("</table>");
        JLabel label = new JLabel(sb.toString());
        label.setSize(label.getPreferredSize());
        BufferedImage image = new BufferedImage(label.getWidth(), label.getHeight(), BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = (Graphics2D) image.getGraphics();
        g2d.setColor(Color.WHITE);
        g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        label.paint(g2d);
        g2d.dispose();
        File file = new File("/tmp/test.png");
        if (!file.getParentFile().exists()) {
            file.getParentFile().mkdirs();
        }
        FileOutputStream baos = null;
        try {
            baos = new FileOutputStream(file);
            ImageIO.write(image, "png", baos);


        Desktop.getDesktop().open(file);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (baos != null) {
                try {
                    baos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

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

        });
    }
}