teaching machines

package lab08;

//  GifSequenceWriter.java
//  
//  Created by Elliot Kroo on 2009-04-25.
//
// This work is licensed under the Creative Commons Attribution 3.0 Unported
// License. To view a copy of this license, visit
// http://creativecommons.org/licenses/by/3.0/ or send a letter to Creative
// Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.

import javax.imageio.*;
import javax.imageio.metadata.*;
import javax.imageio.stream.*;
import java.awt.image.*;
import java.io.*;
import java.util.Iterator;

public class GifSequenceWriter {
  protected ImageWriter gifWriter;
  protected ImageWriteParam imageWriteParam;
  protected IIOMetadata imageMetaData;
  protected ImageOutputStream outputStream;

  /**
   * Creates a new GifSequenceWriter
   * 
   * @param outputStream
   * the ImageOutputStream to be written to
   * @param imageType
   * one of the imageTypes specified in BufferedImage
   * @param timeBetweenFramesMS
   * the time between frames in miliseconds
   * @param loopContinuously
   * wether the gif should loop repeatedly
   * @throws IIOException
   * if no gif ImageWriters are found
   *
   * @author Elliot Kroo (elliot[at]kroo[dot]net)
   */
  public GifSequenceWriter(File outFile,
                           int timeBetweenFramesMS,
                           boolean loopContinuously) {
    try {
      // my method to create a writer
      gifWriter = getWriter();
      imageWriteParam = gifWriter.getDefaultWriteParam();
      ImageTypeSpecifier imageTypeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);

      imageMetaData = gifWriter.getDefaultImageMetadata(imageTypeSpecifier, imageWriteParam);

      String metaFormatName = imageMetaData.getNativeMetadataFormatName();

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

      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");

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

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

      IIOMetadataNode child = new IIOMetadataNode("ApplicationExtension");

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

      int loop = loopContinuously ? 0 : 1;

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

      imageMetaData.setFromTree(metaFormatName, root);

      outputStream = new FileImageOutputStream(outFile);
      gifWriter.setOutput(outputStream);
      gifWriter.prepareWriteSequence(null);
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  public void appendFrame(BufferedImage img) {
    try {
      gifWriter.writeToSequence(new IIOImage(img, null, imageMetaData), imageWriteParam);
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Close this GifSequenceWriter object. This does not close the underlying
   * stream, just finishes off the GIF.
   */
  public void close() {
    try {
      gifWriter.endWriteSequence();
      outputStream.close();
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Returns the first available GIF ImageWriter using
   * ImageIO.getImageWritersBySuffix("gif").
   * 
   * @return a GIF ImageWriter object
   * @throws IIOException
   * if no GIF image writers are returned
   */
  private static ImageWriter getWriter() throws IIOException {
    try {
      Iterator<ImageWriter> iter = ImageIO.getImageWritersBySuffix("gif");
      if (!iter.hasNext()) {
        throw new IIOException("No GIF Image Writers Exist");
      } else {
        return iter.next();
      }
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Returns an existing child node, or creates and returns a new child node (if
   * the requested node does not exist).
   * 
   * @param rootNode
   * the <tt>IIOMetadataNode</tt> to search for the child node.
   * @param nodeName
   * the name of the child node.
   * 
   * @return the child node, if found or a new node created with the given name.
   */
  private static IIOMetadataNode getNode(IIOMetadataNode rootNode,
                                         String nodeName) {
    int nNodes = rootNode.getLength();
    for (int i = 0; i < nNodes; i++) {
      if (rootNode.item(i).getNodeName().compareToIgnoreCase(nodeName) == 0) {
        return ((IIOMetadataNode) rootNode.item(i));
      }
    }
    IIOMetadataNode node = new IIOMetadataNode(nodeName);
    rootNode.appendChild(node);
    return node;
  }
}

File dst = new File(new File(System.getProperty("user.home")), "Desktop/spinner.gif");