How to get screenshot of any Linux/Windows application running outside of the JVM

Question

Is it possible to use Java to get a screenshot of an application external to Java, say VLC/Windows Media Player, store it as an Image object and then display it in a JLabel or something of a similar nature? Does anybody know if this is possible and if so does anybody have a general idea as to how to do it?

Note: I just need to find out how to get a screenshot and store it as some form of Image object. After that I can use, manipulate it, display it, etc.

Answer 1

Here is the answer for Windows (not sure if alt+printScr works on linux :P)

I guess one way to achieve this

1. using Robot class to fire alt+printScreen Command (this captures active window to clipboard)

2. read the clipboard!

Here are the two pieces of code that do that. I have not actually tried, but something that I pieced together.

Code to Fire commands to get active window on clipboard

import java.awt.AWTException;
import java.awt.Robot;
import java.awt.event.KeyEvent;

public class ActiveWindowScreenShot
{
 /**
  * Main method
  * 
  * @param args (not used)
  */
 public static void main(String[] args)
 {
  Robot robot;

  try {
   robot = new Robot();
  } catch (AWTException e) {
   throw new IllegalArgumentException("No robot");
  }

  // Press Alt + PrintScreen
  // (Windows shortcut to take a screen shot of the active window)
  robot.keyPress(KeyEvent.VK_ALT);
  robot.keyPress(KeyEvent.VK_PRINTSCREEN);
  robot.keyRelease(KeyEvent.VK_PRINTSCREEN);
  robot.keyRelease(KeyEvent.VK_ALT);

  System.out.println("Image copied.");
 }
}

Code to read image on clipboard

// If an image is on the system clipboard, this method returns it;
// otherwise it returns null.
public static Image getClipboard() {
    Transferable t = Toolkit.getDefaultToolkit().getSystemClipboard().getContents(null);

    try {
        if (t != null && t.isDataFlavorSupported(DataFlavor.imageFlavor)) {
            Image text = (Image)t.getTransferData(DataFlavor.imageFlavor);
            return text;
        }
    } catch (UnsupportedFlavorException e) {
    } catch (IOException e) {
    }
    return null;
}

You can manage the control as you need to! Let me know if this works for you. but this is certainly on my todo to try it out!