Question

I’m pretty new to Java and SWT, hoping to have one image dissolve into the next. I have one image now in a Label (relevant code):

Device dev = shell.getDisplay();
try {
    Image photo = new Image(dev, "photo.jpg");
} catch(Exception e) { }

Label label = new Label(shell, SWT.IMAGE_JPEG); 
label.setImage(photo);

Now I’d like photo to fade into a different image at a speed that I specify. Is this possible as set up here, or do I need to delve more into the org.eclipse.swt.graphics api?

Also, this will be a slide show that may contain hundreds of photos, only ever moving forward (never back to a previous image)—considering this, is there something I explicitly need to do in order to remove the old images from memory?

Thanks!!

Answer 1

I am not aware of any swt widgets that directly support this type of functionality, your best bet would be to extend org.eclipse.swt.widgets.Canvas and adding a org.eclipse.swt.events.PaintListener that can handle drawing 2 overlapping images with a different alpha. So something like this:

addPaintListener(new PaintListener() {
    public void paintControl(PaintEvent e) {
        e.gc.setAlpha(50);
        e.gc.drawImage(image1, 0, 0);
        e.gc.setAlpha(100);
        e.gc.drawImage(image2, 0, 0);
    }
});

After that you would just have to create a thread change redraw your Canvas and change the images/alpha values at some interval.

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As for your question about removing an Image from memory that is done by calling dispose() on the Image object, letting it get garbage collected won’t be enough when using swt.