title: JavaCV error when saving a captured image
body: <p>This error comes up when I click my Capture button.</p>
  
  <blockquote>
    <p>OpenCV Error: Unspecified error (could not find a writer for the
    specified extension) in cv::imwrite_, file
    C:\build\2_4_winpack-bindings-win64-vc14-static\opencv\modules\highgui\src\loadsave.cpp,
    line 275
        Exception in thread "AWT-EventQueue-0" CvException [org.opencv.core.CvException: cv::Exception:
    C:\build\2_4_winpack-bindings-win64-vc14-static\opencv\modules\highgui\src\loadsave.cpp:275:
    error: (-2) could not find a writer for the specified extension in
    function cv::imwrite_
        ]</p>
  </blockquote>
  
  <p>This is the code for my Capture Button.</p>
  
  <pre><code>if (evt.getSource() == btnCapture) {
      webSource = new VideoCapture(0);
      myThread = new DaemonThread();
      Thread t = new Thread(myThread);
              t.setDaemon(true);
              myThread.runnable = true;
              t.start();
  
          }
  
  myThread.runnable = false;
              webSource.release();
  
  
  
                      JFileChooser jFileChooser1 = new JFileChooser("./images");
                   int returnVal = jFileChooser1.showSaveDialog(this);
  
                  if(returnVal == JFileChooser.APPROVE_OPTION){
                       File  file = jFileChooser1.getSelectedFile().getAbsoluteFile();
                       String path = jFileChooser1.getSelectedFile().getAbsolutePath();
                        f = new File(file.toURI());
                       Highgui.imwrite(file.getPath(), frame);
                  }
  
                  FileInputStream fis;
      try {
          fis = new FileInputStream(f);
           ByteArrayOutputStream bos = new ByteArrayOutputStream();
                  byte[] buf = new byte[1024];
                  for(int readNum; (readNum = fis.read(buf)) != -1;){
                      bos.write(buf, 0, readNum);
      } 
   byte[] convict_image = bos.toByteArray();
      }catch (FileNotFoundException ex) {
          Logger.getLogger(cam.class.getName()).log(Level.SEVERE, null, ex);
      } catch (IOException ex) {
          Logger.getLogger(cam.class.getName()).log(Level.SEVERE, null, ex);
      }
  </code></pre>