Question

i am using Jtree for image list and displaying the selected image, but problem is that if the image size is larger than the canvas size(i.e. 300 X 300) it displays only top left of the image, how to display the whole image in fixed size canvas?

i am using following code:

private void displayImage(File file) {

    try 
    {
        BufferedImage image = ImageIO.read(file);
        ta.Picture = image;
    }
    catch (Exception e) 
    {}

    Graphics g = ta.imageCanvas.getGraphics();
    g.clearRect(0, 0, 300, 300);
    g.drawImage(ta.Picture, 00, 00, this);

} // displayImage

public void valueChanged(TreeSelectionEvent e) 
{
    // TODO Auto-generated method stub
    FileTreeNode node = (FileTreeNode) tree.getLastSelectedPathComponent();

    if (node.isLeaf()) 
    {

        currentFile = node.file;

        File ff = new File("F:/images_blue/" + currentFile.getName());
        displayImage(ff);

    } else
        currentFile = null;

}

Answer 1

I’d just like to point out that…

Graphics g = ta.imageCanvas.getGraphics();
g.clearRect(0, 0, 300, 300);
g.drawImage(ta.Picture, 00, 00, this);

Is a really bad idea.

getGraphics may return null and is, at best, simply a snapshot of the last repaint cycle and could be invalidated or dereferenced on the next paint cycle.

You should be extending from something like JPanel and overriding the paintComponent method. This would allow you to supply a getter and setter as apart of the image management and allow you to produce the scaled image in a self contained and reusable manner

You check out Perfoming Custom Painting for me information

And, as per my comment, you might like to check out these previous questions for examples

• Scale the ImageIcon automatically to label size
• Jpanel resize on repaint
• Quality of Image after resize very low — Java
• Java: maintaining aspect ratio of JPanel background image