Resizing a transparent GIF

Question

Hi There,
I am having trouble getting a transparent gif to resize correctly while preserving the transparency.
I am using the following GIF library to write my image to file:
http://www.shetline.com/cgi-bin/java_formatter.cgi?src=../html/java/org/shetline/io/GIFOutputStream.java&tabwidth=3&log=true
If I load in a gif image and send it straight to the GIFOutputStream, it preserves the transparent level. If I resize the image and send that to the GIFOutputStream, it loses the transparency. This is all happening in a JavaBean called by a Servlet (I am running in headless mode).
The code to resize the image reads:
Image image = Toolkit.getDefaultToolkit().createImage(originalImage);
MediaTracker mediaTracker = new MediaTracker(new Container());
mediaTracker.addImage(image, 0);
mediaTracker.waitForAll();
ByteArrayOutputStream out = new ByteArrayOutputStream();
BufferedImage thumbImage = new BufferedImage(40, 40, BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics2D = thumbImage.createGraphics();
graphics2D.drawImage(image, 0, 0, this.getWidth(), this.getHeight(), this);
// Encode the image as a GIF
Color transparency = getGIFTransparency(thumbImage);
if (transparency == null) {
GIFOutputStream.writeGIF(out, thumbImage, 5);
} else {
GIFOutputStream.writeGIF(out, thumbImage, 5, transparency);
The getGIFTransparency method reads:
private Color getGIFTransparency(Image thisImage) {
MediaTracker mediaTracker = new MediaTracker(new Container());
mediaTracker.addImage(thisImage, 0);
try {
mediaTracker.waitForID(0);
} catch (InterruptedException e) {
Logger.addError(e.toString());
PixelGrabber grabber = new PixelGrabber(thisImage, 0, 0,
thisImage.getWidth(this),
thisImage.getHeight(this),
false);
try {
grabber.grabPixels();
} catch (Exception e) {
Logger.addError(e.toString(), this, "getGIFTransparency");
if (grabber.getColorModel() != null) {
ColorModel colorModel = (ColorModel) grabber.getColorModel();
if (colorModel.getTransparency() != -1) {
return new Color(colorModel.getRGB(colorModel.getTransparency()));
return null;
Any ideas on what I am doing wrong?
Thanks in advance,
Ben

Answer 1

I'm having a similar problem, not exactly with Java 2D but I didn't find a JAI forum:
when I create a new image from 2 BufferedImages, I also have no transparency (and just "add" changes colors because all components of the color are added to each other and green + red = yellow on the screen). I think it has something to do with the initialisation of BufferedImage, but I haven't solved the problem yet. The API says something about BufferedImage being opaque by default. I suppose you have to use a ColorModel in the constructor which is saying that your image is Transparency.Translucent.
If this solves the problem (or if something else works), please do post here, cause I'm looking for a solution too!
Greetings,
Saskia.