Low image quality after zooming in/out

[LianaN]

Hi!

I'm trying to zoom in/out ImageIcon in JLabel. The problem is that after 2-3 zooming actions, the image quality becomes horrible. How could I solve this problem? Thanks!

private void doZoom(int scaleFactor) {
          Component[] c = SelectablePanel.getMainPanel().getComponents();
          for(int i = 0; i < c.length; i++) {
                if(c[i] instanceof JLabel) {                   
                    JLabel selectedLabel = (JLabel)c[i];
                    ImageIcon newIcon = (ImageIcon) selectedLabel.getIcon();
                    Image img = newIcon.getImage();
                    Image newImg = img.getScaledInstance(img.getWidth(null)+scaleFactor, img.getHeight(null)+scaleFactor, java.awt.Image.SCALE_SMOOTH);
                    selectedLabel.setPreferredSize(new Dimension(img.getWidth(null)+scaleFactor, img.getHeight(null)+scaleFactor));
                    newIcon = new ImageIcon(newImg);
                    selectedLabel.setIcon(newIcon);
                }
         }
         repaint();
}

[~s.o.s~]

How could I solve this problem?

By using a high resolution image? If you would try to zoom in on a 128 * 128 image, it would obviously look bad.

Two options AFAICT:
* Use a new image as the image source every time a zoom is done instead of scaling the same low resolution image
* Use vector graphics instead of raster graphics which provide infinite zoom capabilities

[LianaN]

Hi!

Thanks. I improved my code a little bit. However, now a black image is returned instead of rescaled one. (I'm using two images). The problem is with the line newIcon = new ImageIcon(resizeImageHintJpg) . How could this problem be solved?

...
            BufferedImage originalImage;
            try {
                Component[] c = MainClass.getSelectablePanel().getComponents();
                for(int i = 0; i < c.length; i++) {
                    if(c[i] instanceof JLabel) {
                        JLabel selectedLabel = (JLabel)c[i];
                        ImageIcon newIcon = (ImageIcon) selectedLabel.getIcon();
                        Image img = newIcon.getImage();
                        originalImage = new BufferedImage(img.getWidth(null), img.getHeight(null), java.awt.Image.SCALE_SMOOTH);
                        int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB : originalImage.getType();
                        BufferedImage resizeImageHintJpg = resizeImageWithHint(originalImage, type);
                        newIcon = new ImageIcon(resizeImageHintJpg);
                        selectedLabel.setIcon(newIcon);
                    }
                }
                repaint();
            } catch (Exception ex) {
                System.out.println(ex.getMessage());
            }
..

    private static BufferedImage resizeImageWithHint(BufferedImage originalImage, int type){

	BufferedImage resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, type);
	Graphics2D g = resizedImage.createGraphics();
	g.drawImage(originalImage, 0, 0, IMG_WIDTH, IMG_HEIGHT, null);
	g.dispose();
	g.setComposite(AlphaComposite.Src);

	g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
	RenderingHints.VALUE_INTERPOLATION_BILINEAR);
	g.setRenderingHint(RenderingHints.KEY_RENDERING,
	RenderingHints.VALUE_RENDER_QUALITY);
	g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
	RenderingHints.VALUE_ANTIALIAS_ON);

	return resizedImage;
    }