ImageIO.write不能另存为gif，但适用于jpg和png？

我怀疑这里的解决方案可能真的很简单，但是我很困惑……

// Create the buffered image.
BufferedImage bufferedImage = new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);

// fill image data (works fine)
ImageIO.write(bufferedImage, "JPG", f1); // works fine
ImageIO.write(bufferedImage, "PNG", f2); // works fine
ImageIO.write(bufferedImage, "GIF", f3); // this returns false, creates a broken gif file, but fires no exceptions

并ImageIO.write()于GIF不行？这是对gif作为Compuserve专有的东西吗？还是我只是愚蠢（我猜这是最后一个了:)）