J2ME GIF 解码器（支持动画）

Displaying GIF Images on J2ME Mobile Phones 
J2SE GIF Source

第一篇文章讲解比较详细，曾被多次转载。而第二篇则是GIF编解码器的J2SE源代码。

我正是在参考了以上文章之后，才开始对该代码展开移植。包括测试也就用了半天时间。感兴趣的朋友最好自己动手试一试。有麻烦的话，可以联系我。

下面先把J2ME版本的GIF解码器源代码公布如下。稍后提供编码器的代码（工作比较忙，抱歉）。

 
import java.io.InputStream;
import java.util.Vector;

import javax.microedition.lcdui.Image;

/**
 * Class GifDecoder - Decodes a GIF file into one or more frames. <br>
 *
 * <pre>
 * Example:
 *    GifDecoder d = new GifDecoder();
 *    d.read(&quot;sample.gif&quot;);
 *    int n = d.getFrameCount();
 *    for (int i = 0; i &lt; n; i++) {
 *       BufferedImage frame = d.getFrame(i);  // frame i
 *       int t = d.getDelay(i);  // display duration of frame in milliseconds
 *       // do something with frame
 *    }
 * </pre>
 *
 * No copyright asserted on the source code of this class. May be used for any
 * purpose, however, refer to the Unisys LZW patent for any additional
 * restrictions. Please forward any corrections to kweiner@fmsware.com.
 *
 * @author Kevin Weiner, FM Software; LZW decoder adapted from John Cristy's
 *         ImageMagick.
 * @version 1.03 November 2003
 *
 */

public class GifDecoder {

    /**
     * File read status: No errors.
     */
    public static final int STATUS_OK = 0;

    /**
     * File read status: Error decoding file (may be partially decoded)
     */
    public static final int STATUS_FORMAT_ERROR = 1;

    /**
     * File read status: Unable to open source.
     */
    public static final int STATUS_OPEN_ERROR = 2;

    protected InputStream in;
    protected int status;

    protected int width; // full image width
    protected int height; // full image height
    protected boolean gctFlag; // global color table used
    protected int gctSize; // size of global color table
    protected int loopCount = 1; // iterations; 0 = repeat forever

    protected int[] gct; // global color table
    protected int[] lct; // local color table
    protected int[] act; // active color table

    protected int bgIndex; // background color index
    protected int bgColor; // background color
    protected int lastBgColor; // previous bg color
    protected int pixelAspect; // pixel aspect ratio

    protected boolean lctFlag; // local color table flag
    protected boolean interlace; // interlace flag
    protected int lctSize; // local color table size

    protected int ix, iy, iw, ih; // current image rectangle
    protected int lrx, lry, lrw, lrh;
    protected Image image; // current frame
    protected Image lastImage; // previous frame

    protected byte[] block = new byte[256]; // current data block