GifMaker

import javax.imageio.*;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.metadata.IIOMetadataNode;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;

/**
 * @author sci4me
 */
public final class GifMaker
{
    private final int width, height;
    private final int imageType;
    private BufferedImage currentFrame;

    private ImageWriter gifWriter;
    private ImageWriteParam imageWriteParam;
    private IIOMetadata imageMetaData;

    public GifMaker(final OutputStream out, final int timeBetweenFramesMS, final int width, final int height) throws IOException
    {
        this(out, timeBetweenFramesMS, BufferedImage.TYPE_INT_RGB, width, height);
    }

    public GifMaker(final OutputStream out, final int timeBetweenFramesMS, final int imageType, final int width, final int height) throws IOException
    {
        this(out, timeBetweenFramesMS, imageType, true, width, height);
    }

    public GifMaker(final OutputStream out, final int timeBetweenFramesMS, final int imageType, final boolean loopContinuously, final int width, final int height) throws IOException
    {
        this.width = width;
        this.height = height;
        this.imageType = imageType;
        this.currentFrame = new BufferedImage(width, height, this.imageType);

        this.gifWriter = this.getWriter();
        this.imageWriteParam = this.gifWriter.getDefaultWriteParam();
        final ImageTypeSpecifier imageTypeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(this.imageType);

        this.imageMetaData = this.gifWriter.getDefaultImageMetadata(imageTypeSpecifier, this.imageWriteParam);

        final String metaFormatName = this.imageMetaData.getNativeMetadataFormatName();

        final IIOMetadataNode root = (IIOMetadataNode) this.imageMetaData.getAsTree(metaFormatName);

        final IIOMetadataNode graphicsControlExtensionNode = getNode(root, "GraphicControlExtension");

        graphicsControlExtensionNode.setAttribute("disposalMethod", "none");
        graphicsControlExtensionNode.setAttribute("userInputFlag", "FALSE");
        graphicsControlExtensionNode.setAttribute("transparentColorFlag", "FALSE");
        graphicsControlExtensionNode.setAttribute("delayTime", Integer.toString(timeBetweenFramesMS / 10));
        graphicsControlExtensionNode.setAttribute("transparentColorIndex", "0");

        final IIOMetadataNode commentsNode = getNode(root, "CommentExtensions");
        commentsNode.setAttribute("CommentExtension", "Created by MAH");

        final IIOMetadataNode appEntensionsNode = getNode(root, "ApplicationExtensions");

        final IIOMetadataNode child = new IIOMetadataNode("ApplicationExtension");

        child.setAttribute("applicationID", "NETSCAPE");
        child.setAttribute("authenticationCode", "2.0");

        final int loop = loopContinuously ? 0 : 1;

        child.setUserObject(new byte[]{0x1, (byte) (loop & 0xFF), (byte) ((loop >> 8) & 0xFF)});
        appEntensionsNode.appendChild(child);

        this.imageMetaData.setFromTree(metaFormatName, root);
        this.gifWriter.setOutput(ImageIO.createImageOutputStream(out));
        this.gifWriter.prepareWriteSequence(null);
    }

    public GifMaker fill(final int startX, final int startY, final int width, final int height, final int color)
    {
        for (int x = 0; x < width; x++)
            for (int y = 0; y < height; y++)
                this.setPixel(startX + x, startY + y, color);

        return this;
    }

    public GifMaker setPixel(final int x, final int y, final int color)
    {
        this.currentFrame.setRGB(x, y, color);
        return this;
    }

    public GifMaker nextFrame() throws IOException
    {
        this.gifWriter.writeToSequence(new IIOImage(this.currentFrame, null, this.imageMetaData), this.imageWriteParam);
        this.currentFrame = new BufferedImage(this.width, this.height, this.imageType);
        return this;
    }

    public GifMaker write() throws IOException
    {
        this.gifWriter.endWriteSequence();
        return this;
    }

    private static ImageWriter getWriter() throws IIOException
    {
        final Iterator<ImageWriter> iter = ImageIO.getImageWritersBySuffix("gif");
        if (!iter.hasNext())
        {
            throw new IIOException("No GIF Image Writers Exist");
        }
        else
        {
            return iter.next();
        }
    }

    private static IIOMetadataNode getNode(final IIOMetadataNode rootNode, final String nodeName)
    {
        final int nNodes = rootNode.getLength();
        for (int i = 0; i < nNodes; i++)
        {
            if (rootNode.item(i).getNodeName().compareToIgnoreCase(nodeName) == 0)
            {
                return ((IIOMetadataNode) rootNode.item(i));
            }
        }
        final IIOMetadataNode node = new IIOMetadataNode(nodeName);
        rootNode.appendChild(node);
        return (node);
    }
}