import javax.imageio.metadata.*;
import javax.imageio.stream.*;

sclass GIFRewriter {
  settable File inputFile;
  settable bool debug;
  byte[] data;
  int numImages;
  ImageReader reader;
  S metaFormatName;
  
  Image get() ctex {
    if (!inputFile.exists()) null;

    // Load anything but GIF the normal way
    if (!isGIF(inputFile))
      ret ImageIO.read(inputFile);
    
    reader = ImageIO.getImageReadersByFormatName("gif").next();
    // Give it the stream to decode from
    reader.setInput(ImageIO.createImageInputStream(inputFile));
  
    numImages = reader.getNumImages(true);
  
    // Get 'metaFormatName'. Need first frame for that.
    IIOMetadata imageMetaData = reader.getImageMetadata(0);
    metaFormatName = imageMetaData.getNativeMetadataFormatName();
  
    // Prepare streams for image encoding
    new ByteArrayOutputStream baoStream;
    
    {
      temp ImageOutputStream ios = ImageIO.createImageOutputStream(baoStream);
      // Get GIF writer that's compatible with reader
      ImageWriter writer = ImageIO.getImageWriter(reader);
      // Give it the stream to encode to
      writer.setOutput(ios);

      writer.prepareWriteSequence(null);

      for i to numImages: {
        // Get input image
        BufferedImage frameIn = reader.read(i);
        
        frameIn = transformImage(frameIn);

        // Get input metadata
        IIOMetadataNode root = (IIOMetadataNode)reader.getImageMetadata(i).getAsTree(metaFormatName);

        // Find GraphicControlExtension node
        int nNodes = root.getLength();
        for j to nNodes: {
          org.w3c.dom.Node node = root.item(j);
          if (node.getNodeName().equalsIgnoreCase("GraphicControlExtension")) {
            cast node to IIOMetadataNode;
            if (parseInt(node.getAttribute("delayTime")) == 0)
              node.setAttribute("delayTime", "10");
          }
  
          // Create output metadata
          IIOMetadata metadata = writer.getDefaultImageMetadata(new ImageTypeSpecifier(frameIn), null);
          // Copy metadata to output metadata
          metadata.setFromTree(metadata.getNativeMetadataFormatName(), root);
  
          // Create output image
          IIOImage frameOut = new IIOImage(frameIn, null, metadata);

          // Encode output image
          writer.writeToSequence(frameOut, writer.getDefaultWriteParam());
        }
  
        writer.endWriteSequence();
      }
  
      // Create image using encoded data
      data = baoStream.toByteArray();
      if (debug) print("Data size: " + l(data));
      ret Toolkit.getDefaultToolkit().createImage(data);
    }
  }
  
  bool animationSpeedIsBugged() ctex {
    for i to numImages: {
      IIOMetadataNode root = cast reader.getImageMetadata(i).getAsTree(metaFormatName);

      int nNodes = root.getLength();
      for j to nNodes: {
        org.w3c.dom.Node node = root.item(j);
        if (node.getNodeName().equalsIgnoreCase("GraphicControlExtension")) {
          cast node to IIOMetadataNode;
          if (parseInt(node.getAttribute("delayTime")) == 0) true;
        }
      }
    }
    false;
  }
  
  swappable BufferedImage transformImage(BufferedImage image) { ret image; }
}

Began life as a copy of #1015991