public static void writeAnimGif(int framerate, int repetitions,java.util.Iterator<java.awt.image.RenderedImage> producer, java.io.File file) throws java.io.IOException
{
	int milliseconds=1000/framerate;
	javax.imageio.ImageWriter writer=javax.imageio.ImageIO.getImageWritersByFormatName("gif").next();
	javax.imageio.ImageWriteParam imageWriteParam = writer.getDefaultWriteParam();
	javax.imageio.ImageTypeSpecifier imageTypeSpecifier = javax.imageio.ImageTypeSpecifier.createFromBufferedImageType(java.awt.image.BufferedImage.TYPE_BYTE_INDEXED);
	javax.imageio.metadata.IIOMetadata iioMetaData =writer.getDefaultImageMetadata(imageTypeSpecifier,imageWriteParam);
	String metaFormatName = iioMetaData.getNativeMetadataFormatName();
	javax.imageio.metadata.IIOMetadataNode root = (javax.imageio.metadata.IIOMetadataNode)iioMetaData.getAsTree(metaFormatName);
	javax.imageio.metadata.IIOMetadataNode graphicsControlExtensionNode = getOrAddNode(root,"GraphicControlExtension");
	graphicsControlExtensionNode.setAttribute("disposalMethod", "none");
	graphicsControlExtensionNode.setAttribute("userInputFlag", "FALSE");
	graphicsControlExtensionNode.setAttribute("transparentColorFlag", "FALSE");
	//ticks are 10 ms each
	graphicsControlExtensionNode.setAttribute("delayTime", java.lang.Integer.toString(milliseconds / 10));
	graphicsControlExtensionNode.setAttribute("transparentColorIndex", "0");

	//number of repetitions - so 1 means two loops:
	//1 run + 1 repetition. 0 is a special case meaning run forever - therefore if only one run without any repetitions
	//is wished for, the setting of the user object needs to be omitted...
	if(repetitions!=0)
	{
		javax.imageio.metadata.IIOMetadataNode appEntensionsNode = getOrAddNode(root, "ApplicationExtensions");
		javax.imageio.metadata.IIOMetadataNode child = new javax.imageio.metadata.IIOMetadataNode("ApplicationExtension");

		//Needs to be that value for repetitions to work correctly
		child.setAttribute("applicationID", "NETSCAPE");
		child.setAttribute("authenticationCode", "2.0");

		int loop = repetitions < 0 ? 0 : repetitions;

		child.setUserObject(new byte[]{0x1, (byte) (loop & 0xFF), (byte) ((loop >> 8) & 0xFF)});
		appEntensionsNode.appendChild(child);
	}
	iioMetaData.setFromTree(metaFormatName, root);
	javax.imageio.stream.ImageOutputStream outputStream=new javax.imageio.stream.FileImageOutputStream(file);
	writer.setOutput(outputStream);
	writer.prepareWriteSequence(null);
	while(producer.hasNext())
	{
		javax.imageio.IIOImage iioImage = new javax.imageio.IIOImage(producer.next(), null, iioMetaData);
		writer.writeToSequence(iioImage, imageWriteParam);
	}
	writer.endWriteSequence();
	outputStream.close();

}
private static javax.imageio.metadata.IIOMetadataNode getOrAddNode(javax.imageio.metadata.IIOMetadataNode root, String name)
{
	javax.imageio.metadata.IIOMetadataNode rv=null;
	for (int i = 0; i < root.getLength(); ++i)
	{
		if (root.item(i).getNodeName().compareToIgnoreCase(name) == 0) {
			rv=(javax.imageio.metadata.IIOMetadataNode) root.item(i);
		}
	}
	if(rv==null)
	{
		rv = new javax.imageio.metadata.IIOMetadataNode(name);
		root.appendChild(rv);
	}
	return(rv);
}

class Producer extends Object implements java.util.Iterator<java.awt.image.RenderedImage>
{
    private final int stepsize;
    private final int frames;
    private final java.awt.Paint paint;
    private int counter;
    private final java.awt.Stroke stroke = new java.awt.BasicStroke(5f);

    Producer(int stepsize, int frames, Paint paint)
    {
        super();
        this.stepsize = stepsize;
        this.frames = frames;
        this.paint = paint;
    }

    @Override
    public boolean hasNext()
    {
        return counter < 40;
    }

    @Override
    public java.awt.image.RenderedImage next()
    {
        java.awt.image.BufferedImage bimg = new java.awt.image.BufferedImage(640, 480, java.awt.image.BufferedImage.TYPE_BYTE_INDEXED);
        java.awt.Graphics2D g2 = bimg.createGraphics();
        g2.setRenderingHint(java.awt.RenderingHints.KEY_ANTIALIASING, java.awt.RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(java.awt.Color.WHITE);
        g2.setStroke(stroke);
        g2.fillRect(0, 0, 640, 480);
        g2.setPaint(paint);
        g2.drawOval(counter * stepsize, counter * stepsize, 200, 200);
        g2.dispose();
        ++counter;
        return bimg;
    }
}