how to save a GIF without losing transparency?

Java 2D
#1

hi everyone,

does anyone know how to load a gif file, scale it and the save the result as a new gif without losing transparency?? im using an encoder called Gif89Encoder. so far i have only tried to load a gif and the save the image as a new file, the result looks just like the original but without transparency :’(

here is a small example


//test method
public static void main(String args[]) {
      Image image = null;
      try {
            image = loadImage("input.gif");
      } catch(Exception ex) {
            //...
      }
      
      if(image != null) {
            ColorModel cm = getColorModel(image);
            IndexColorModel icm = null;
            int transindex = -1;
            if(cm instanceof IndexColorModel) {
                  icm = (IndexColorModel)cm;
                  transindex = icm.getTransparentPixel(); // image in this test had transindex = 97 
            }
            try {
                  BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("out.gif"));
                  Gif89Encoder gifenc = new Gif89Encoder(image);
                  gifenc.setTransparentIndex(transindex);
                  gifenc.getFrameAt(0).setInterlaced(false);
                  gifenc.encode(out);
            } catch(Exception e) {
                  //...
            }
      }
}

//loading the original gif image
private Image loadImage(String path) throws FileNotFoundException, InterruptedException {
      File f = new File(path);
      if(!f.exists()) {
            throw new FileNotFoundException();
      }
      f = null;
            
      Image image = null;
      try {
            image = Toolkit.getDefaultToolkit().getImage(path);
            MediaTracker tracker = new MediaTracker(new Frame());
            tracker.addImage(image, 0);
            tracker.waitForID(0);
                  
            if (tracker.isErrorAny()) {
                  //...
            }
                  
            return image;
      } catch(InterruptedException ex) {
            throw new InterruptedException();
      }
}

//get colormodel from the original image
private ColorModel getColorModel(Image image) {
      PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
      try {
            pg.grabPixels();
      } catch (InterruptedException ex) {
            ex.printStackTrace(System.out);
      }
      return pg.getColorModel();
}

if anyone can help, maybe an example or advice, i would really appreciate it!!!

best regards,
javamunky

#2

We had similar problems with gif encoding (loosing transparency, bad quality output images, “more than 256 colors” exception) but just some days ago we found the new gif animation & encoding library Gif4J (http://www.gif4j.com). It’s commercial but very powerful, really easy to use and solves all our problems ;D

#3

The JAI Image I/O Tools release 1.0_01 includes a GIFImageWriter, so you may want to give that a try:
http://java.sun.com/developer/earlyAccess/jai_imageio/index.html

Unless you’re bound to JDK 1.1, you’d be much better off using more modern approaches (e.g. BufferedImage instead of PixelGrabber/MediaTracker/etc). For example (once you’ve installed the above libraries):
BufferedImage img = ImageIO.read(“input.gif”);
// do stuff with img
ImageIO.write(img, “gif”, new File(“out.gif”));

It’s just that simple, and should have no difficulties preserving transparency.

Hope this helps,
Chris

#4

[quote]The JAI Image I/O Tools release 1.0_01 includes a GIFImageWriter, so you may want to give that a try:
http://java.sun.com/developer/earlyAccess/jai_imageio/index.html

Unless you’re bound to JDK 1.1, you’d be much better off using more modern approaches (e.g. BufferedImage instead of PixelGrabber/MediaTracker/etc). For example (once you’ve installed the above libraries):
BufferedImage img = ImageIO.read(“input.gif”);
// do stuff with img
ImageIO.write(img, “gif”, new File(“out.gif”));

It’s just that simple, and should have no difficulties preserving transparency.

Hope this helps,
Chris
[/quote]
Yes, but to use JAI you should download and install it anywhere you plan to deploy your solutions…
And Gif4J also supports ImageIO…

#5

hi,

thanks for all replies, appreciate it! i tried a few different encoders and with some changes i got it working with the acme gifencoder.

cheers,
javamunky