Question

I am using the Background Panel class for background images on my JPanels. So far I have succeeded in Gradients, SCALED images and ACTUAL images but if I set the style of the background to TILED, the Desktop Application fails/crashes, it opens but the window is empty (see through) and I have to Stop the application to close it. I am not getting any errors in my console.

Here is the Custom Code on my JPanel:

jPanel2 = new BackgroundPanel(imgHeader, BackgroundPanel.TILED);

My image is defined earlier on:

final Image imgHeader = java.awt.Toolkit.getDefaultToolkit().getImage(getClass().getResource("/images/headerBar.gif"));

I added logging statements to the Background Panel class

private void drawTiled(Graphics g) {
    Dimension d = getSize();
    int width = image.getWidth(null); // returning as -1. should be 1
    int height = image.getHeight(null); // returning as 48. Correct!

    for (int x = 0; x < d.width; x += width) {
        System.err.println("outer for imgW" + width + " panelW " + d.width + " newW " + x);
        for (int y = 0; y < d.height; y += height) {
            g.drawImage(image, x, y, null, null);
            System.err.println("inner for" + height);
        }
    }
}

I found that width = -1 therefor causing an endless loop. The width of the image is actually 1 pixel. The height (48 pixles) is correct. I got the same result when I changed the width of the image to 48 pixels.

More Tests: When I set the width to 48, the height returns -1.

Why is the image width returning as -1?

Answer 1

From the java api:

Returns: the width of this image, or -1 if the width is not yet known.

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To resolve the problem you could use ImageIO.read(InputStream). It will fully read the image (creating an BufferedImage).

final Image imgHeader = 
         ImageIO.read(getClass().getResourceAsStream("/images/headerBar.gif"));

You can then use the image.getWidth() and image.getHeight() methods to get the size of the image.