Getting problem in accessing web cam

Question

I have written code in Java to access web cam,and to save image... I am getting following exceptions : Exception in thread "main" java.lang.NullPointerException at SwingCapture.(SwingCapture.java:40) at SwingCapture.main(SwingCapture.java:66)

how to remove this exceptions.

here is the code:

import javax.swing.*;

import javax.swing.event.; import java.io.; import javax.media.; import javax.media.format.; import javax.media.util.; import javax.media.control.; import javax.media.protocol.; import java.util.; import java.awt.; import java.awt.image.; import java.awt.event.; import com.sun.image.codec.jpeg.;

public class SwingCapture extends Panel implements ActionListener { public static Player player = null; public CaptureDeviceInfo di = null; public MediaLocator ml = null; public JButton capture = null; public Buffer buf = null; public Image img = null; public VideoFormat vf = null; public BufferToImage btoi = null; public ImagePanel imgpanel = null;

public SwingCapture() { setLayout(new BorderLayout()); setSize(320,550);

imgpanel = new ImagePanel();
capture = new JButton("Capture");
capture.addActionListener(this);


String str1 = "vfw:iNTEX IT-308 WC:0";
String str2 = "vfw:Microsoft WDM Image Capture (Win32):0";
di = CaptureDeviceManager.getDevice(str2);
ml = di.getLocator();

try 
{
  player = Manager.createRealizedPlayer(ml);
  player.start();
  Component comp;

  if ((comp = player.getVisualComponent()) != null)
  {
    add(comp,BorderLayout.NORTH);
  }
  add(capture,BorderLayout.CENTER);
  add(imgpanel,BorderLayout.SOUTH);
} 
catch (Exception e) 
{
  e.printStackTrace();
}

}

public static void main(String[] args) { Frame f = new Frame("SwingCapture"); SwingCapture cf = new SwingCapture();

f.addWindowListener(new WindowAdapter() {
  public void windowClosing(WindowEvent e) {
  playerclose();
  System.exit(0);}});

f.add("Center",cf);
f.pack();
f.setSize(new Dimension(320,550));
f.setVisible(true);

}

public static void playerclose() { player.close(); player.deallocate(); }

public void actionPerformed(ActionEvent e) { JComponent c = (JComponent) e.getSource();

if (c == capture) 
{
  // Grab a frame
  FrameGrabbingControl fgc = (FrameGrabbingControl)
  player.getControl("javax.media.control.FrameGrabbingControl");
  buf = fgc.grabFrame();

  // Convert it to an image
  btoi = new BufferToImage((VideoFormat)buf.getFormat());
  img = btoi.createImage(buf);

  // show the image
  imgpanel.setImage(img);

  // save image
  saveJPG(img,"\test.jpg");
}

}

class ImagePanel extends Panel { public Image myimg = null;

public ImagePanel() 
{
  setLayout(null);
  setSize(320,240);
}

public void setImage(Image img) 
{
  this.myimg = img;
  repaint();
}

public void paint(Graphics g) 
{
  if (myimg != null) 
  {
    g.drawImage(myimg, 0, 0, this);
  }
}

}

public static void saveJPG(Image img, String s) { BufferedImage bi = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_RGB); Graphics2D g2 = bi.createGraphics(); g2.drawImage(img, null, null);

FileOutputStream out = null;
try
{ 
  out = new FileOutputStream(s); 
}
catch (java.io.FileNotFoundException io)
{ 
  System.out.println("File Not Found"); 
}

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
param.setQuality(0.5f,false);
encoder.setJPEGEncodeParam(param);

try 
{ 
  encoder.encode(bi); 
  out.close(); 
}
catch (java.io.IOException io) 
{
  System.out.println("IOException"); 
}

}

So that's the line ml = di.getLocator();, which is preceded by di = CaptureDeviceManager.getDevice(str2);. I guess CaptureDeviceManager.getDevice returned null, probably for a reason listed in its API docs. — Tom Hawtin - tackline
String str2 = "vfw:Microsoft WDM Image Capture (Win32):0"; this is for MS Windows, I am using Ubuntu Linux.. I think there must be replacement for this line in Linux. — Chetan

Samurai Samurai · Accepted Answer · 2010-03-30T07:00:58

If you are using built in web cam most of the time it shows errors. You can try with external web cam.

Getting problem in accessing web cam

3 Answers