Generate Animated GIFs

[Riven]

It’s a nightmare to find the code to create animated GIFs in Java. Once you found it, you notice you can’t set the frame disposal, and transparent pixels will show pixels in the previous frames. The following code snippet solves this.

First I’ll show how you’ll actually use this code to create a frame sequence:

   List<GifFrame> gifFrames = new ArrayList<GifFrame>();

   for(BufferedImage image: images)
   {
      int transparantColor = 0xFF00FF; // purple
      BufferedImage gif = convertRGBAToGIF(image, transparantColor);

      // every frame takes 100ms
      long delay = 100;

      // make transparent pixels not 'shine through'
      String disposal = GifFrame.RESTORE_TO_BGCOLOR;

      // add frame to sequence
      gifFrames.add(new GifFrame(gif, delay, disposal));
   }

   int loopCount = 0; // loop indefinitely
   saveAnimatedGIF(outputStream, gifFrames, loopCount);

Here is the implementation:

public class GifFrame
{
   public static final String NONE                = "none";
   public static final String DO_NOT_DISPOSE      = "doNotDispose";
   public static final String RESTORE_TO_BGCOLOR  = "restoreToBackgroundColor";
   public static final String RESTORE_TO_PREVIOUS = "restoreToPrevious";

   public final BufferedImage img;
   public final long          delay; // in millis
   public final String        disposalMethod;

   public GifFrame(BufferedImage img, long delay)
   {
      this(img, delay, NONE);
   }

   public GifFrame(BufferedImage img, long delay, String disposalMethod)
   {
      this.img = img;
      this.delay = delay;
      this.disposalMethod = disposalMethod;
   }
}

public class ImageUtil
{
   public static BufferedImage convertRGBAToGIF(BufferedImage src, int transColor)
   {
      BufferedImage dst = new BufferedImage(src.getWidth(), src.getHeight(), BufferedImage.TYPE_BYTE_INDEXED);
      Graphics g = dst.getGraphics();
      g.setColor(new Color(transColor));
      g.fillRect(0, 0, dst.getWidth(), dst.getHeight());
      {
         IndexColorModel indexedModel = (IndexColorModel) dst.getColorModel();
         WritableRaster raster = dst.getRaster();
         int sample = raster.getSample(0, 0, 0);
         int size = indexedModel.getMapSize();
         byte[] rr = new byte[size];
         byte[] gg = new byte[size];
         byte[] bb = new byte[size];
         indexedModel.getReds(rr);
         indexedModel.getGreens(gg);
         indexedModel.getBlues(bb);
         IndexColorModel newModel = new IndexColorModel(8, size, rr, gg, bb, sample);
         dst = new BufferedImage(newModel, raster, dst.isAlphaPremultiplied(), null);
      }
      dst.createGraphics().drawImage(src, 0, 0, null);
      return dst;
   }

   public static void saveAnimatedGIF(OutputStream out, List<GifFrame> frames, int loopCount) throws Exception
   {
      ImageWriter iw = ImageIO.getImageWritersByFormatName("gif").next();

      ImageOutputStream ios = ImageIO.createImageOutputStream(out);
      iw.setOutput(ios);
      iw.prepareWriteSequence(null);

      int p = 0;
      for (GifFrame frame : frames)
      {
         ImageWriteParam iwp = iw.getDefaultWriteParam();
         IIOMetadata metadata = iw.getDefaultImageMetadata(new ImageTypeSpecifier(frame.img), iwp);
         ImageUtil.configureGIFFrame(metadata, String.valueOf(frame.delay / 10L), p++, frame.disposalMethod, loopCount);
         IIOImage ii = new IIOImage(frame.img, null, metadata);
         iw.writeToSequence(ii, null);
      }

      iw.endWriteSequence();
      ios.close();
   }

   private static void configureGIFFrame(IIOMetadata meta, String delayTime, int imageIndex, String disposalMethod, int loopCount)
   {
      String metaFormat = meta.getNativeMetadataFormatName();

      if (!"javax_imageio_gif_image_1.0".equals(metaFormat))
      {
         throw new IllegalArgumentException("Unfamiliar gif metadata format: " + metaFormat);
      }

      Node root = meta.getAsTree(metaFormat);

      Node child = root.getFirstChild();
      while (child != null)
      {
         if ("GraphicControlExtension".equals(child.getNodeName()))
            break;
         child = child.getNextSibling();
      }

      IIOMetadataNode gce = (IIOMetadataNode) child;
      gce.setAttribute("userDelay", "FALSE");
      gce.setAttribute("delayTime", delayTime);
      gce.setAttribute("disposalMethod", disposalMethod);

      if (imageIndex == 0)
      {
         IIOMetadataNode aes = new IIOMetadataNode("ApplicationExtensions");
         IIOMetadataNode ae = new IIOMetadataNode("ApplicationExtension");
         ae.setAttribute("applicationID", "NETSCAPE");
         ae.setAttribute("authenticationCode", "2.0");
         byte[] uo = new byte[] { 0x1, (byte) (loopCount & 0xFF), (byte) ((loopCount >> 8) & 0xFF) };
         ae.setUserObject(uo);
         aes.appendChild(ae);
         root.appendChild(aes);
      }

      try
      {
         meta.setFromTree(metaFormat, root);
      }
      catch (IIOInvalidTreeException e)
      {
         throw new Error(e);
      }
   }
}

[ra4king]

You are amazing!