ImageIO image renders slow in scroll pane

Question

Hello all, I need some help understanding the behavior of BufferedImage(s)
retrieved from ImageIO.read(). The problem I am having is weird .. I load
a PNG image via ImageIO.read(), I use it to construct an ImageIcon which
is later used in a JLabel/JScrollPane for rendering. When I attempt
to scroll the image in the scroll pane, it is very chunky and slow.
If I load the same image with ImageIcon(byte[]), there is no problem. The
image on disk is 186k, when loaded from ImageIcon(), it consumes about
10M, when loaded with ImageIO about 5M is consumed ... when I scroll,
the memory usage increase about 9 MB, which can be collected immediatly
to return to 5M.
Is ImageIO doing some fancy optimization to preserve memory, if so ... how
can I alter the settings or turn it off completly. I tried setting
ImageIO.setUseCache(false); that did nothing as far as I can tell.
The code to load the image is as follows, I am just using the default right now.
      // perform base64 decoding from buffer
      ByteArrayInputStream bos = new ByteArrayInputStream(decoded);
      try
         image = ImageIO.read(bos);
      catch (IOException ioe)
      }Any help would be greatly appreciated!!!
Cheers,
Jody

Answer 1

I'm not sure if this is exactly what you are looking for but, here's code that works well for me:
private class MyJLabel extends JLabel {
    public void paintComponent(Graphics g) {
      super.paintComponent(g);
      Graphics2D g2d = (Graphics2D)g;
      URL imageLocation = MyJPanel.class.getResource("myImage.jpg");
      Image myImage = Toolkit.getDefaultToolkit().getImage (imageLocation);
      MediaTracker tracker = new MediaTracker (this);
      tracker.addImage(myImage, 0);
      try { tracker.waitForID(0); } catch (InterruptedException exception) { System.out.println("Image myImage.jpg wasn't loaded!"); }
      g2d.drawImage(myImage, 0, 0, getWidth(), getHeight, this);
}Once I reload images using the above method, image repainting is very quick. Extend the JLabel (MyJLabel) to overwrite the paint method as above. Should work fast when you do so. You can move the image retrieving code out of the paint method and into the 'MyJLabel' constructor.
How are you painting the icon and where are you retrieving the image? Can you post more code?
Regards,
Devyn