Gif动图压缩java版

简单说明下，如果不是压缩动图的话只用java本身的包足够实现压缩和截取图片了，为了能够压缩gif动图，这里引用了两个文件

AnimatedGifEncoder 和  GifDecoder， 

先用Decoder来获取到gif的文件信息（每帧的图片，帧与帧的间隔……），然后用一个循环来处理每帧图片，同时新建一个Encoder，其它信息照搬Decoder获取到的，只有每帧的图片都单独压缩处理下，最终完成版的就是压缩后的。

在ImageUtils中有main方法，展示了如何压缩图片的，并计算了压缩一个gif的平均耗时，实验采用的是一个三帧的简单gif动图，平均用时0.6s左右，还是不错的。

　　　　　　　// 开始于1520496592958, 结束于1520496629281, 平均用时605毫秒. 60次
            // 开始于1520496686684, 结束于1520496757617, 平均用时591毫秒. 120次
            // 开始于1520496805643, 结束于1520496876973, 平均用时594毫秒. 120次
            // 开始于1520496915209, 结束于1520496983136, 平均用时566毫秒. 120次
            // 开始于1520497090507, 结束于1520497125541, 平均用时583毫秒. 60次
            // 开始于1520497218145, 结束于1520497330390, 平均用时561毫秒. 200次
            // 开始于1520497363505, 结束于1520497645334, 平均用时563毫秒. 500次

import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Class AnimatedGifEncoder - Encodes a GIF file consisting of one or more
 * frames.
 * <p>
 * <pre>
 *  Example:
 *     AnimatedGifEncoder e = new AnimatedGifEncoder();
 *     e.start(outputFileName);
 *     e.setDelay(1000);   // 1 frame per sec
 *     e.addFrame(image1);
 *     e.addFrame(image2);
 *     e.finish();
 * </pre>
 * <p>
 * No copyright asserted on the source code of this class. May be used for any
 * purpose, however, refer to the Unisys LZW patent for restrictions on use of
 * the associated LZWEncoder class. Please forward any corrections to
 * kweiner@fmsware.com.
 *
 * @author Kevin Weiner, FM Software
 * @version 1.03 November 2003
 */

public class AnimatedGifEncoder {

    protected int width; // image size

    protected int height;

    protected Color transparent = null; // transparent color if given

    protected int transIndex; // transparent index in color table

    protected int repeat = -1; // no repeat

    protected int delay = 0; // frame delay (hundredths)

    protected boolean started = false; // ready to output frames

    protected OutputStream out;

    protected BufferedImage image; // current frame

    protected byte[] pixels; // BGR byte array from frame

    protected byte[] indexedPixels; // converted frame indexed to palette

    protected int colorDepth; // number of bit planes

    protected byte[] colorTab; // RGB palette

    protected boolean[] usedEntry = new boolean[256]; // active palette entries

    protected int palSize = 7; // color table size (bits-1)

    protected int dispose = -1; // disposal code (-1 = use default)

    protected boolean closeStream = false; // close stream when finished

    protected boolean firstFrame = true;

    protected boolean sizeSet = false; // if false, get size from first frame

    protected int sample = 10; // default sample interval for quantizer

    /**
     * Sets the delay time between each frame, or changes it for subsequent frames
     * (applies to last frame added).
     *
     * @param ms int delay time in milliseconds
     */
    public void setDelay(int ms) {
        delay = Math.round(ms / 10.0f);
    }

    /**
     * Sets the GIF frame disposal code for the last added frame and any
     * subsequent frames. Default is 0 if no transparent color has been set,
     * otherwise 2.
     *
     * @param code int disposal code.
     */
    public void setDispose(int code) {
        if (code >= 0) {
            dispose = code;
        }
    }

    /**
     * Sets the number of times the set of GIF frames should be played. Default is
     * 1; 0 means play indefinitely. Must be invoked before the first image is
     * added.
     *
     * @param iter int number of iterations.
     * @return
     */
    public void setRepeat(int iter) {
        if (iter >= 0) {
            repeat = iter;
        }
    }

    /**
     * Sets the transparent color for the last added frame and any subsequent
     * frames. Since all colors are subject to modification in the quantization
     * process, the color in the final palette for each frame closest to the given
     * color becomes the transparent color for that frame. May be set to null to
     * indicate no transparent color.
     *
     * @param c Color to be treated as transparent on display.
     */
    public void setTransparent(Color c) {
        transparent = c;
    }

    /**
     * Adds next GIF frame. The frame is not written immediately, but is actually
     * deferred until the next frame is received so that timing data can be
     * inserted. Invoking <code>finish()</code> flushes all frames. If
     * <code>setSize</code> was not invoked, the size of the first image is used
     * for all subsequent frames.
     *
     * @param im BufferedImage containing frame to write.
     * @return true if successful.
     */
    public boolean addFrame(BufferedImage im) {
        if ((im == null) || !started) {
            return false;
        }
        boolean ok = true;
        try {
            if (!sizeSet) {
                // use first frame's size
                setSize(im.getWidth(), im.getHeight());
            }
            image = im;
            getImagePixels(); // convert to correct format if necessary
            analyzePixels(); // build color table & map pixels
            if (firstFrame) {
                writeLSD(); // logical screen descriptior
                writePalette(); // global color table
                if (repeat >= 0) {
                    // use NS app extension to indicate reps
                    writeNetscapeExt();
                }
            }
            writeGraphicCtrlExt(); // write graphic control extension
            writeImageDesc(); // image descriptor
            if (!firstFrame) {
                writePalette(); // local color table
            }
            writePixels(); // encode and write pixel data
            firstFrame = false;
        } catch (IOException e) {
            ok = false;
        }

        return ok;
    }

    /**
     * Flushes any pending data and closes output file. If writing to an
     * OutputStream, the stream is not closed.
     */
    public boolean finish() {
        if (!started)
            return false;
        boolean ok = true;
        started = false;
        try {
            out.write(0x3b); // gif trailer
            out.flush();
            if (closeStream) {
                out.close();
            }
        } catch (IOException e) {
            ok = false;
        }

        // reset for subsequent use
        transIndex = 0;
        out = null;
        image = null;
        pixels = null;
        indexedPixels = null;
        colorTab = null;
        closeStream = false;
        firstFrame = true;

        return ok;
    }

    /**
     * Sets frame rate in frames per second. Equivalent to
     * <code>setDelay(1000/fps)</code>.
     *
     * @param fps float frame rate (frames per second)
     */
    public void setFrameRate(float fps) {
        if (fps != 0f) {
            delay = Math.round(100f / fps);
        }
    }

    /**
     * Sets quality of color quantization (conversion of images to the maximum 256
     * colors allowed by the GIF specification). Lower values (minimum = 1)
     * produce better colors, but slow processing significantly. 10 is the
     * default, and produces good color mapping at reasonable speeds. Values
     * greater than 20 do not yield significant improvements in speed.
     *
     * @param quality int greater than 0.
     * @return
     */
    public void setQuality(int quality) {
        if (quality < 1)
            quality = 1;
        sample = quality;
    }

    /**
     * Sets the GIF frame size. The default size is the size of the first frame
     * added if this method is not invoked.
     *
     * @param w int frame width.
     * @param h int frame width.
     */
    public void setSize(int w, int h) {
        if (started && !firstFrame)
            return;
        width = w;
        height = h;
        if (width < 1)
            width = 320;
        if (height < 1)
            height = 240;
        sizeSet = true;
    }

    /**
     * Initiates GIF file creation on the given stream. The stream is not closed
     * automatically.
     *
     * @param os OutputStream on which GIF images are written.
     * @return false if initial write failed.
     */
    public boolean start(OutputStream os) {
        if (os == null)
            return false;
        boolean ok = true;
        closeStream = false;
        out = os;
        try {
            writeString("GIF89a"); // header
        } catch (IOException e) {
            ok = false;
        }
        return started = ok;
    }

    /**
     * Initiates writing of a GIF file with the specified name.
     *
     * @param file String containing output file name.
     * @return false if open or initial write failed.
     */
    public boolean start(String file) {
        boolean ok = true;
        try {
            out = new BufferedOutputStream(new FileOutputStream(file));
            ok = start(out);
            closeStream = true;
        } catch (IOException e) {
            ok = false;
        }
        return started = ok;
    }

    /**
     * Analyzes image colors and creates color map.
     */
    protected void analyzePixels() {
        int len = pixels.length;
        int nPix = len / 3;
        indexedPixels = new byte[nPix];
        NeuQuant nq = new NeuQuant(pixels, len, sample);
        // initialize quantizer
        colorTab = nq.process(); // create reduced palette
        // convert map from BGR to RGB
        for (int i = 0; i < colorTab.length; i += 3) {
            byte temp = colorTab[i];
            colorTab[i] = colorTab[i + 2];
            colorTab[i + 2] = temp;
            usedEntry[i / 3] = false;
        }
        // map image pixels to new palette
        int k = 0;
        for (int i = 0; i < nPix; i++) {
            int index = nq.map(pixels[k++] & 0xff, pixels[k++] & 0xff, pixels[k++] & 0xff);
            usedEntry[index] = true;
            indexedPixels[i] = (byte) index;
        }
        pixels = null;
        colorDepth = 8;
        palSize = 7;
        // get closest match to transparent color if specified
        if (transparent != null) {
            transIndex = findClosest(transparent);
        }
    }

    /**
     * Returns index of palette color closest to c
     */
    protected int findClosest(Color c) {
        if (colorTab == null)
            return -1;
        int r = c.getRed();
        int g = c.getGreen();
        int b = c.getBlue();
        int minpos = 0;
        int dmin = 256 * 256 * 256;
        int len = colorTab.length;
        for (int i = 0; i < len; ) {
            int dr = r - (colorTab[i++] & 0xff);
            int dg = g - (colorTab[i++] & 0xff);
            int db = b - (colorTab[i] & 0xff);
            int d = dr * dr + dg * dg + db * db;
            int index = i / 3;
            if (usedEntry[index] && (d < dmin)) {
                dmin = d;
                minpos = index;
            }
            i++;
        }
        return minpos;
    }

    /**
     * Extracts image pixels into byte array "pixels"
     */
    protected void getImagePixels() {
        int w = image.getWidth();
        int h = image.getHeight();
        int type = image.getType();
        if ((w != width) || (h != height) || (type != BufferedImage.TYPE_3BYTE_BGR)) {
            // create new image with right size/format
            BufferedImage temp = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
            Graphics2D g = temp.createGraphics();
            g.drawImage(image, 0, 0, null);
            image = temp;
        }
        pixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
    }

    /**
     * Writes Graphic Control Extension
     */
    protected void writeGraphicCtrlExt() throws IOException {
        out.write(0x21); // extension introducer
        out.write(0xf9); // GCE label
        out.write(4); // data block size
        int transp, disp;
        if (transparent == null) {
            transp = 0;
            disp = 0; // dispose = no action
        } else {
            transp = 1;
            disp = 2; // force clear if using transparent color
        }
        if (dispose >= 0) {
            disp = dispose & 7; // user override
        }
        disp <<= 2;

        // packed fields
        out.write(0 | // 1:3 reserved
                disp | // 4:6 disposal
                0 | // 7 user input - 0 = none
                transp); // 8 transparency flag

        writeShort(delay); // delay x 1/100 sec
        out.write(transIndex); // transparent color index
        out.write(0); // block terminator
    }

    /**
     * Writes Image Descriptor
     */
    protected void writeImageDesc() throws IOException {
        out.write(0x2c); // image separator
        writeShort(0); // image position x,y = 0,0
        writeShort(0);
        writeShort(width); // image size
        writeShort(height);
        // packed fields
        if (firstFrame) {
            // no LCT - GCT is used for first (or only) frame
            out.write(0);
        } else {
            // specify normal LCT
            out.write(0x80 | // 1 local color table 1=yes
                    0 | // 2 interlace - 0=no
                    0 | // 3 sorted - 0=no
                    0 | // 4-5 reserved
                    palSize); // 6-8 size of color table
        }
    }

    /**
     * Writes Logical Screen Descriptor
     */
    protected void writeLSD() throws IOException {
        // logical screen size
        writeShort(width);
        writeShort(height);
        // packed fields
        out.write((0x80 | // 1 : global color table flag = 1 (gct used)
                0x70 | // 2-4 : color resolution = 7
                0x00 | // 5 : gct sort flag = 0
                palSize)); // 6-8 : gct size

        out.write(0); // background color index
        out.write(0); // pixel aspect ratio - assume 1:1
    }

    /**
     * Writes Netscape application extension to define repeat count.
     */
    protected void writeNetscapeExt() throws IOException {
        out.write(0x21); // extension introducer
        out.write(0xff); // app extension label
        out.write(11); // block size
        writeString("NETSCAPE" + "2.0"); // app id + auth code
        out.write(3); // sub-block size
        out.write(1); // loop sub-block id
        writeShort(repeat); // loop count (extra iterations, 0=repeat forever)
        out.write(0); // block terminator
    }

    /**
     * Writes color table
     */
    protected void writePalette() throws IOException {
        out.write(colorTab, 0, colorTab.length);
        int n = (3 * 256) - colorTab.length;
        for (int i = 0; i < n; i++) {
            out.write(0);
        }
    }

    /**
     * Encodes and writes pixel data
     */
    protected void writePixels() throws IOException {
        LZWEncoder encoder = new LZWEncoder(width, height, indexedPixels, colorDepth);
        encoder.encode(out);
    }

    /**
     * Write 16-bit value to output stream, LSB first
     */
    protected void writeShort(int value) throws IOException {
        out.write(value & 0xff);
        out.write((value >> 8) & 0xff);
    }

    /**
     * Writes string to output stream
     */
    protected void writeString(String s) throws IOException {
        for (int i = 0; i < s.length(); i++) {
            out.write((byte) s.charAt(i));
        }
    }
}

/*
 * NeuQuant Neural-Net Quantization Algorithm
 * ------------------------------------------
 *
 * Copyright (c) 1994 Anthony Dekker
 *
 * NEUQUANT Neural-Net quantization algorithm by Anthony Dekker, 1994. See
 * "Kohonen neural networks for optimal colour quantization" in "Network:
 * Computation in Neural Systems" Vol. 5 (1994) pp 351-367. for a discussion of
 * the algorithm.
 *
 * Any party obtaining a copy of these files from the author, directly or
 * indirectly, is granted, free of charge, a full and unrestricted irrevocable,
 * world-wide, paid up, royalty-free, nonexclusive right and license to deal in
 * this software and documentation files (the "Software"), including without
 * limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons who
 * receive copies from any such party to do so, with the only requirement being
 * that this copyright notice remain intact.
 */

// Ported to Java 12/00 K Weiner
class NeuQuant {

    protected static final int netsize = 256; /* number of colours used */

    /* four primes near 500 - assume no image has a length so large */
  /* that it is divisible by all four primes */
    protected static final int prime1 = 499;

    protected static final int prime2 = 491;

    protected static final int prime3 = 487;

    protected static final int prime4 = 503;

    protected static final int minpicturebytes = (3 * prime4);

  /* minimum size for input image */

  /*
   * Program Skeleton ---------------- [select samplefac in range 1..30] [read
   * image from input file] pic = (unsigned char*) malloc(3*width*height);
   * initnet(pic,3*width*height,samplefac); learn(); unbiasnet(); [write output
   * image header, using writecolourmap(f)] inxbuild(); write output image using
   * inxsearch(b,g,r)
   */

  /*
   * Network Definitions -------------------
   */

    protected static final int maxnetpos = (netsize - 1);

    protected static final int netbiasshift = 4; /* bias for colour values */

    protected static final int ncycles = 100; /* no. of learning cycles */

    /* defs for freq and bias */
    protected static final int intbiasshift = 16; /* bias for fractions */

    protected static final int intbias = (((int) 1) << intbiasshift);

    protected static final int gammashift = 10; /* gamma = 1024 */

    protected static final int gamma = (((int) 1) << gammashift);

    protected static final int betashift = 10;

    protected static final int beta = (intbias >> betashift); /* beta = 1/1024 */

    protected static final int betagamma = (intbias << (gammashift - betashift));

    /* defs for decreasing radius factor */
    protected static final int initrad = (netsize >> 3); /*
                                                         * for 256 cols, radius
                                                         * starts
                                                         */

    protected static final int radiusbiasshift = 6; /* at 32.0 biased by 6 bits */

    protected static final int radiusbias = (((int) 1) << radiusbiasshift);

    protected static final int initradius = (initrad * radiusbias); /*
                                                                   * and
                                                                   * decreases
                                                                   * by a
                                                                   */

    protected static final int radiusdec = 30; /* factor of 1/30 each cycle */

    /* defs for decreasing alpha factor */
    protected static final int alphabiasshift = 10; /* alpha starts at 1.0 */

    protected static final int initalpha = (((int) 1) << alphabiasshift);

    protected int alphadec; /* biased by 10 bits */

    /* radbias and alpharadbias used for radpower calculation */
    protected static final int radbiasshift = 8;

    protected static final int radbias = (((int) 1) << radbiasshift);

    protected static final int alpharadbshift = (alphabiasshift + radbiasshift);

    protected static final int alpharadbias = (((int) 1) << alpharadbshift);

  /*
   * Types and Global Variables --------------------------
   */

    protected byte[] thepicture; /* the input image itself */

    protected int lengthcount; /* lengthcount = H*W*3 */

    protected int samplefac; /* sampling factor 1..30 */

    // typedef int pixel[4]; /* BGRc */
    protected int[][] network; /* the network itself - [netsize][4] */

    protected int[] netindex = new int[256];

  /* for network lookup - really 256 */

    protected int[] bias = new int[netsize];

    /* bias and freq arrays for learning */
    protected int[] freq = new int[netsize];

    protected int[] radpower = new int[initrad];

  /* radpower for precomputation */

    /*
     * Initialise network in range (0,0,0) to (255,255,255) and set parameters
     * -----------------------------------------------------------------------
     */
    public NeuQuant(byte[] thepic, int len, int sample) {

        int i;
        int[] p;

        thepicture = thepic;
        lengthcount = len;
        samplefac = sample;

        network = new int[netsize][];
        for (i = 0; i < netsize; i++) {
            network[i] = new int[4];
            p = network[i];
            p[0] = p[1] = p[2] = (i << (netbiasshift + 8)) / netsize;
            freq[i] = intbias / netsize; /* 1/netsize */
            bias[i] = 0;
        }
    }

    public byte[] colorMap() {
        byte[] map = new byte[3 * netsize];
        int[] index = new int[netsize];
        for (int i = 0; i < netsize; i++)
            index[network[i][3]] = i;
        int k = 0;
        for (int i = 0; i < netsize; i++) {
            int j = index[i];
            map[k++] = (byte) (network[j][0]);
            map[k++] = (byte) (network[j][1]);
            map[k++] = (byte) (network[j][2]);
        }
        return map;
    }

    /*
     * Insertion sort of network and building of netindex[0..255] (to do after
     * unbias)
     * -------------------------------------------------------------------------------
     */
    public void inxbuild() {

        int i, j, smallpos, smallval;
        int[] p;
        int[] q;
        int previouscol, startpos;

        previouscol = 0;
        startpos = 0;
        for (i = 0; i < netsize; i++) {
            p = network[i];
            smallpos = i;
            smallval = p[1]; /* index on g */
      /* find smallest in i..netsize-1 */
            for (j = i + 1; j < netsize; j++) {
                q = network[j];
                if (q[1] < smallval) { /* index on g */
                    smallpos = j;
                    smallval = q[1]; /* index on g */
                }
            }
            q = network[smallpos];
      /* swap p (i) and q (smallpos) entries */
            if (i != smallpos) {
                j = q[0];
                q[0] = p[0];
                p[0] = j;
                j = q[1];
                q[1] = p[1];
                p[1] = j;
                j = q[2];
                q[2] = p[2];
                p[2] = j;
                j = q[3];
                q[3] = p[3];
                p[3] = j;
            }
      /* smallval entry is now in position i */
            if (smallval != previouscol) {
                netindex[previouscol] = (startpos + i) >> 1;
                for (j = previouscol + 1; j < smallval; j++)
                    netindex[j] = i;
                previouscol = smallval;
                startpos = i;
            }
        }
        netindex[previouscol] = (startpos + maxnetpos) >> 1;
        for (j = previouscol + 1; j < 256; j++)
            netindex[j] = maxnetpos; /* really 256 */
    }

    /*
     * Main Learning Loop ------------------
     */
    public void learn() {

        int i, j, b, g, r;
        int radius, rad, alpha, step, delta, samplepixels;
        byte[] p;
        int pix, lim;

        if (lengthcount < minpicturebytes)
            samplefac = 1;
        alphadec = 30 + ((samplefac - 1) / 3);
        p = thepicture;
        pix = 0;
        lim = lengthcount;
        samplepixels = lengthcount / (3 * samplefac);
        delta = samplepixels / ncycles;
        alpha = initalpha;
        radius = initradius;

        rad = radius >> radiusbiasshift;
        if (rad <= 1)
            rad = 0;
        for (i = 0; i < rad; i++)
            radpower[i] = alpha * (((rad * rad - i * i) * radbias) / (rad * rad));

        // fprintf(stderr,"beginning 1D learning: initial radius=%d\n", rad);

        if (lengthcount < minpicturebytes)
            step = 3;
        else if ((lengthcount % prime1) != 0)
            step = 3 * prime1;
        else {
            if ((lengthcount % prime2) != 0)
                step = 3 * prime2;
            else {
                if ((lengthcount % prime3) != 0)
                    step = 3 * prime3;
                else
                    step = 3 * prime4;
            }
        }

        i = 0;
        while (i < samplepixels) {
            b = (p[pix + 0] & 0xff) << netbiasshift;
            g = (p[pix + 1] & 0xff) << netbiasshift;
            r = (p[pix + 2] & 0xff) << netbiasshift;
            j = contest(b, g, r);

            altersingle(alpha, j, b, g, r);
            if (rad != 0)
                alterneigh(rad, j, b, g, r); /* alter neighbours */

            pix += step;
            if (pix >= lim)
                pix -= lengthcount;

            i++;
            if (delta == 0)
                delta = 1;
            if (i % delta == 0) {
                alpha -= alpha / alphadec;
                radius -= radius / radiusdec;
                rad = radius >> radiusbiasshift;
                if (rad <= 1)
                    rad = 0;
                for (j = 0; j < rad; j++)
                    radpower[j] = alpha * (((rad * rad - j * j) * radbias) / (rad * rad));
            }
        }
        // fprintf(stderr,"finished 1D learning: final alpha=%f
        // !\n",((float)alpha)/initalpha);
    }

    /*
     * Search for BGR values 0..255 (after net is unbiased) and return colour
     * index
     * ----------------------------------------------------------------------------
     */
    public int map(int b, int g, int r) {

        int i, j, dist, a, bestd;
        int[] p;
        int best;

        bestd = 1000; /* biggest possible dist is 256*3 */
        best = -1;
        i = netindex[g]; /* index on g */
        j = i - 1; /* start at netindex[g] and work outwards */

        while ((i < netsize) || (j >= 0)) {
            if (i < netsize) {
                p = network[i];
                dist = p[1] - g; /* inx key */
                if (dist >= bestd)
                    i = netsize; /* stop iter */
                else {
                    i++;
                    if (dist < 0)
                        dist = -dist;
                    a = p[0] - b;
                    if (a < 0)
                        a = -a;
                    dist += a;
                    if (dist < bestd) {
                        a = p[2] - r;
                        if (a < 0)
                            a = -a;
                        dist += a;
                        if (dist < bestd) {
                            bestd = dist;
                            best = p[3];
                        }
                    }
                }
            }
            if (j >= 0) {
                p = network[j];
                dist = g - p[1]; /* inx key - reverse dif */
                if (dist >= bestd)
                    j = -1; /* stop iter */
                else {
                    j--;
                    if (dist < 0)
                        dist = -dist;
                    a = p[0] - b;
                    if (a < 0)
                        a = -a;
                    dist += a;
                    if (dist < bestd) {
                        a = p[2] - r;
                        if (a < 0)
                            a = -a;
                        dist += a;
                        if (dist < bestd) {
                            bestd = dist;
                            best = p[3];
                        }
                    }
                }
            }
        }
        return (best);
    }

    public byte[] process() {
        learn();
        unbiasnet();
        inxbuild();
        return colorMap();
    }

    /*
     * Unbias network to give byte values 0..255 and record position i to prepare
     * for sort
     * -----------------------------------------------------------------------------------
     */
    public void unbiasnet() {

        int i, j;

        for (i = 0; i < netsize; i++) {
            network[i][0] >>= netbiasshift;
            network[i][1] >>= netbiasshift;
            network[i][2] >>= netbiasshift;
            network[i][3] = i; /* record colour no */
        }
    }

    /*
     * Move adjacent neurons by precomputed alpha*(1-((i-j)^2/[r]^2)) in
     * radpower[|i-j|]
     * ---------------------------------------------------------------------------------
     */
    protected void alterneigh(int rad, int i, int b, int g, int r) {

        int j, k, lo, hi, a, m;
        int[] p;

        lo = i - rad;
        if (lo < -1)
            lo = -1;
        hi = i + rad;
        if (hi > netsize)
            hi = netsize;

        j = i + 1;
        k = i - 1;
        m = 1;
        while ((j < hi) || (k > lo)) {
            a = radpower[m++];
            if (j < hi) {
                p = network[j++];
                try {
                    p[0] -= (a * (p[0] - b)) / alpharadbias;
                    p[1] -= (a * (p[1] - g)) / alpharadbias;
                    p[2] -= (a * (p[2] - r)) / alpharadbias;
                } catch (Exception e) {
                } // prevents 1.3 miscompilation
            }
            if (k > lo) {
                p = network[k--];
                try {
                    p[0] -= (a * (p[0] - b)) / alpharadbias;
                    p[1] -= (a * (p[1] - g)) / alpharadbias;
                    p[2] -= (a * (p[2] - r)) / alpharadbias;
                } catch (Exception e) {
                }
            }
        }
    }

    /*
     * Move neuron i towards biased (b,g,r) by factor alpha
     * ----------------------------------------------------
     */
    protected void altersingle(int alpha, int i, int b, int g, int r) {

    /* alter hit neuron */
        int[] n = network[i];
        n[0] -= (alpha * (n[0] - b)) / initalpha;
        n[1] -= (alpha * (n[1] - g)) / initalpha;
        n[2] -= (alpha * (n[2] - r)) / initalpha;
    }

    /*
     * Search for biased BGR values ----------------------------
     */
    protected int contest(int b, int g, int r) {

    /* finds closest neuron (min dist) and updates freq */
    /* finds best neuron (min dist-bias) and returns position */
    /* for frequently chosen neurons, freq[i] is high and bias[i] is negative */
    /* bias[i] = gamma*((1/netsize)-freq[i]) */

        int i, dist, a, biasdist, betafreq;
        int bestpos, bestbiaspos, bestd, bestbiasd;
        int[] n;

        bestd = ~(((int) 1) << 31);
        bestbiasd = bestd;
        bestpos = -1;
        bestbiaspos = bestpos;

        for (i = 0; i < netsize; i++) {
            n = network[i];
            dist = n[0] - b;
            if (dist < 0)
                dist = -dist;
            a = n[1] - g;
            if (a < 0)
                a = -a;
            dist += a;
            a = n[2] - r;
            if (a < 0)
                a = -a;
            dist += a;
            if (dist < bestd) {
                bestd = dist;
                bestpos = i;
            }
            biasdist = dist - ((bias[i]) >> (intbiasshift - netbiasshift));
            if (biasdist < bestbiasd) {
                bestbiasd = biasdist;
                bestbiaspos = i;
            }
            betafreq = (freq[i] >> betashift);
            freq[i] -= betafreq;
            bias[i] += (betafreq << gammashift);
        }
        freq[bestpos] += beta;
        bias[bestpos] -= betagamma;
        return (bestbiaspos);
    }
}

// ==============================================================================
// Adapted from Jef Poskanzer's Java port by way of J. M. G. Elliott.
// K Weiner 12/00

class LZWEncoder {

    private static final int EOF = -1;

    private int imgW, imgH;

    private byte[] pixAry;

    private int initCodeSize;

    private int remaining;

    private int curPixel;

    // GIFCOMPR.C - GIF Image compression routines
    //
    // Lempel-Ziv compression based on 'compress'. GIF modifications by
    // David Rowley (mgardi@watdcsu.waterloo.edu)

    // General DEFINEs

    static final int BITS = 12;

    static final int HSIZE = 5003; // 80% occupancy

    // GIF Image compression - modified 'compress'
    //
    // Based on: compress.c - File compression ala IEEE Computer, June 1984.
    //
    // By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
    // Jim McKie (decvax!mcvax!jim)
    // Steve Davies (decvax!vax135!petsd!peora!srd)
    // Ken Turkowski (decvax!decwrl!turtlevax!ken)
    // James A. Woods (decvax!ihnp4!ames!jaw)
    // Joe Orost (decvax!vax135!petsd!joe)

    int n_bits; // number of bits/code

    int maxbits = BITS; // user settable max # bits/code

    int maxcode; // maximum code, given n_bits

    int maxmaxcode = 1 << BITS; // should NEVER generate this code

    int[] htab = new int[HSIZE];

    int[] codetab = new int[HSIZE];

    int hsize = HSIZE; // for dynamic table sizing

    int free_ent = 0; // first unused entry

    // block compression parameters -- after all codes are used up,
    // and compression rate changes, start over.
    boolean clear_flg = false;

    // Algorithm: use open addressing double hashing (no chaining) on the
    // prefix code / next character combination. We do a variant of Knuth's
    // algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
    // secondary probe. Here, the modular division first probe is gives way
    // to a faster exclusive-or manipulation. Also do block compression with
    // an adaptive reset, whereby the code table is cleared when the compression
    // ratio decreases, but after the table fills. The variable-length output
    // codes are re-sized at this point, and a special CLEAR code is generated
    // for the decompressor. Late addition: construct the table according to
    // file size for noticeable speed improvement on small files. Please direct
    // questions about this implementation to ames!jaw.

    int g_init_bits;

    int ClearCode;

    int EOFCode;

    // output
    //
    // Output the given code.
    // Inputs:
    // code: A n_bits-bit integer. If == -1, then EOF. This assumes
    // that n_bits =< wordsize - 1.
    // Outputs:
    // Outputs code to the file.
    // Assumptions:
    // Chars are 8 bits long.
    // Algorithm:
    // Maintain a BITS character long buffer (so that 8 codes will
    // fit in it exactly). Use the VAX insv instruction to insert each
    // code in turn. When the buffer fills up empty it and start over.

    int cur_accum = 0;

    int cur_bits = 0;

    int masks[] = {0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, 0x01FF,
            0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF};

    // Number of characters so far in this 'packet'
    int a_count;

    // Define the storage for the packet accumulator
    byte[] accum = new byte[256];

    // ----------------------------------------------------------------------------
    LZWEncoder(int width, int height, byte[] pixels, int color_depth) {
        imgW = width;
        imgH = height;
        pixAry = pixels;
        initCodeSize = Math.max(2, color_depth);
    }

    // Add a character to the end of the current packet, and if it is 254
    // characters, flush the packet to disk.
    void char_out(byte c, OutputStream outs) throws IOException {
        accum[a_count++] = c;
        if (a_count >= 254)
            flush_char(outs);
    }

    // Clear out the hash table

    // table clear for block compress
    void cl_block(OutputStream outs) throws IOException {
        cl_hash(hsize);
        free_ent = ClearCode + 2;
        clear_flg = true;

        output(ClearCode, outs);
    }

    // reset code table
    void cl_hash(int hsize) {
        for (int i = 0; i < hsize; ++i)
            htab[i] = -1;
    }

    void compress(int init_bits, OutputStream outs) throws IOException {
        int fcode;
        int i /* = 0 */;
        int c;
        int ent;
        int disp;
        int hsize_reg;
        int hshift;

        // Set up the globals: g_init_bits - initial number of bits
        g_init_bits = init_bits;

        // Set up the necessary values
        clear_flg = false;
        n_bits = g_init_bits;
        maxcode = MAXCODE(n_bits);

        ClearCode = 1 << (init_bits - 1);
        EOFCode = ClearCode + 1;
        free_ent = ClearCode + 2;

        a_count = 0; // clear packet

        ent = nextPixel();

        hshift = 0;
        for (fcode = hsize; fcode < 65536; fcode *= 2)
            ++hshift;
        hshift = 8 - hshift; // set hash code range bound

        hsize_reg = hsize;
        cl_hash(hsize_reg); // clear hash table

        output(ClearCode, outs);

        outer_loop:
        while ((c = nextPixel()) != EOF) {
            fcode = (c << maxbits) + ent;
            i = (c << hshift) ^ ent; // xor hashing

            if (htab[i] == fcode) {
                ent = codetab[i];
                continue;
            } else if (htab[i] >= 0) // non-empty slot
            {
                disp = hsize_reg - i; // secondary hash (after G. Knott)
                if (i == 0)
                    disp = 1;
                do {
                    if ((i -= disp) < 0)
                        i += hsize_reg;

                    if (htab[i] == fcode) {
                        ent = codetab[i];
                        continue outer_loop;
                    }
                } while (htab[i] >= 0);
            }
            output(ent, outs);
            ent = c;
            if (free_ent < maxmaxcode) {
                codetab[i] = free_ent++; // code -> hashtable
                htab[i] = fcode;
            } else
                cl_block(outs);
        }
        // Put out the final code.
        output(ent, outs);
        output(EOFCode, outs);
    }

    // ----------------------------------------------------------------------------
    void encode(OutputStream os) throws IOException {
        os.write(initCodeSize); // write "initial code size" byte

        remaining = imgW * imgH; // reset navigation variables
        curPixel = 0;

        compress(initCodeSize + 1, os); // compress and write the pixel data

        os.write(0); // write block terminator
    }

    // Flush the packet to disk, and reset the accumulator
    void flush_char(OutputStream outs) throws IOException {
        if (a_count > 0) {
            outs.write(a_count);
            outs.write(accum, 0, a_count);
            a_count = 0;
        }
    }

    final int MAXCODE(int n_bits) {
        return (1 << n_bits) - 1;
    }

    // ----------------------------------------------------------------------------
    // Return the next pixel from the image
    // ----------------------------------------------------------------------------
    private int nextPixel() {
        if (remaining == 0)
            return EOF;

        --remaining;

        byte pix = pixAry[curPixel++];

        return pix & 0xff;
    }

    void output(int code, OutputStream outs) throws IOException {
        cur_accum &= masks[cur_bits];

        if (cur_bits > 0)
            cur_accum |= (code << cur_bits);
        else
            cur_accum = code;

        cur_bits += n_bits;

        while (cur_bits >= 8) {
            char_out((byte) (cur_accum & 0xff), outs);
            cur_accum >>= 8;
            cur_bits -= 8;
        }

        // If the next entry is going to be too big for the code size,
        // then increase it, if possible.
        if (free_ent > maxcode || clear_flg) {
            if (clear_flg) {
                maxcode = MAXCODE(n_bits = g_init_bits);
                clear_flg = false;
            } else {
                ++n_bits;
                if (n_bits == maxbits)
                    maxcode = maxmaxcode;
                else
                    maxcode = MAXCODE(n_bits);
            }
        }

        if (code == EOFCode) {
            // At EOF, write the rest of the buffer.
            while (cur_bits > 0) {
                char_out((byte) (cur_accum & 0xff), outs);
                cur_accum >>= 8;
                cur_bits -= 8;
            }

            flush_char(outs);
        }
    }
}

import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;

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 BufferedInputStream 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 Rectangle lastRect; // last image rect
    protected BufferedImage image; // current frame
    protected BufferedImage lastImage; // previous frame

    protected byte[] block = new byte[256]; // current data block
    protected int blockSize = 0; // block size

    // last graphic control extension info
    protected int dispose = 0;
    // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
    protected int lastDispose = 0;
    protected boolean transparency = false; // use transparent color
    protected int delay = 0; // delay in milliseconds
    protected int transIndex; // transparent color index

    protected static final int MaxStackSize = 4096;
    // max decoder pixel stack size

    // LZW decoder working arrays
    protected short[] prefix;
    protected byte[] suffix;
    protected byte[] pixelStack;
    protected byte[] pixels;

    protected ArrayList frames; // frames read from current file
    protected int frameCount;

    static class GifFrame {
        public GifFrame(BufferedImage im, int del) {
            image = im;
            delay = del;
        }

        public BufferedImage image;
        public int delay;
    }

    /**
     * Gets display duration for specified frame.
     *
     * @param n int index of frame
     * @return delay in milliseconds
     */
    public int getDelay(int n) {
        //
        delay = -1;
        if ((n >= 0) && (n < frameCount)) {
            delay = ((GifFrame) frames.get(n)).delay;
        }
        return delay;
    }

    /**
     * Gets the number of frames read from file.
     *
     * @return frame count
     */
    public int getFrameCount() {
        return frameCount;
    }

    /**
     * Gets the first (or only) image read.
     *
     * @return BufferedImage containing first frame, or null if none.
     */
    public BufferedImage getImage() {
        return getFrame(0);
    }

    /**
     * Gets the "Netscape" iteration count, if any.
     * A count of 0 means repeat indefinitiely.
     *
     * @return iteration count if one was specified, else 1.
     */
    public int getLoopCount() {
        return loopCount;
    }

    /**
     * Creates new frame image from current data (and previous
     * frames as specified by their disposition codes).
     */
    protected void setPixels() {
        // expose destination image's pixels as int array
        int[] dest =
                ((DataBufferInt) image.getRaster().getDataBuffer()).getData();

        // fill in starting image contents based on last image's dispose code
        if (lastDispose > 0) {
            if (lastDispose == 3) {
                // use image before last
                int n = frameCount - 2;
                if (n > 0) {
                    lastImage = getFrame(n - 1);
                } else {
                    lastImage = null;
                }
            }

            if (lastImage != null) {
                int[] prev =
                        ((DataBufferInt) lastImage.getRaster().getDataBuffer()).getData();
                System.arraycopy(prev, 0, dest, 0, width * height);
                // copy pixels

                if (lastDispose == 2) {
                    // fill last image rect area with background color
                    Graphics2D g = image.createGraphics();
                    Color c = null;
                    if (transparency) {
                        c = new Color(0, 0, 0, 0);  // assume background is transparent
                    } else {
                        c = new Color(lastBgColor); // use given background color
                    }
                    g.setColor(c);
                    g.setComposite(AlphaComposite.Src); // replace area
                    g.fill(lastRect);
                    g.dispose();
                }
            }
        }

        // copy each source line to the appropriate place in the destination
        int pass = 1;
        int inc = 8;
        int iline = 0;
        for (int i = 0; i < ih; i++) {
            int line = i;
            if (interlace) {
                if (iline >= ih) {
                    pass++;
                    switch (pass) {
                        case 2:
                            iline = 4;
                            break;
                        case 3:
                            iline = 2;
                            inc = 4;
                            break;
                        case 4:
                            iline = 1;
                            inc = 2;
                    }
                }
                line = iline;
                iline += inc;
            }
            line += iy;
            if (line < height) {
                int k = line * width;
                int dx = k + ix; // start of line in dest
                int dlim = dx + iw; // end of dest line
                if ((k + width) < dlim) {
                    dlim = k + width; // past dest edge
                }
                int sx = i * iw; // start of line in source
                while (dx < dlim) {
                    // map color and insert in destination
                    int index = ((int) pixels[sx++]) & 0xff;
                    int c = act[index];
                    if (c != 0) {
                        dest[dx] = c;
                    }
                    dx++;
                }
            }
        }
    }

    /**
     * Gets the image contents of frame n.
     *
     * @return BufferedImage representation of frame, or null if n is invalid.
     */
    public BufferedImage getFrame(int n) {
        BufferedImage im = null;
        if ((n >= 0) && (n < frameCount)) {
            im = ((GifFrame) frames.get(n)).image;
        }
        return im;
    }

    /**
     * Gets image size.
     *
     * @return GIF image dimensions
     */
    public Dimension getFrameSize() {
        return new Dimension(width, height);
    }

    /**
     * Reads GIF image from stream
     *
     * @param BufferedInputStream containing GIF file.
     * @return read status code (0 = no errors)
     */
    public int read(BufferedInputStream is) {
        init();
        if (is != null) {
            in = is;
            readHeader();
            if (!err()) {
                readContents();
                if (frameCount < 0) {
                    status = STATUS_FORMAT_ERROR;
                }
            }
        } else {
            status = STATUS_OPEN_ERROR;
        }
        try {
            is.close();
        } catch (IOException e) {
        }
        return status;
    }

    /**
     * Reads GIF image from stream
     *
     * @param InputStream containing GIF file.
     * @return read status code (0 = no errors)
     */
    public int read(InputStream is) {
        init();
        if (is != null) {
            if (!(is instanceof BufferedInputStream))
                is = new BufferedInputStream(is);
            in = (BufferedInputStream) is;
            readHeader();
            if (!err()) {
                readContents();
                if (frameCount < 0) {
                    status = STATUS_FORMAT_ERROR;
                }
            }
        } else {
            status = STATUS_OPEN_ERROR;
        }
        try {
            is.close();
        } catch (IOException e) {
        }
        return status;
    }

    /**
     * Reads GIF file from specified file/URL source
     * (URL assumed if name contains ":/" or "file:")
     *
     * @param name String containing source
     * @return read status code (0 = no errors)
     */
    public int read(String name) {
        status = STATUS_OK;
        try {
            name = name.trim().toLowerCase();
            if ((name.indexOf("file:") >= 0) ||
                    (name.indexOf(":/") > 0)) {
                URL url = new URL(name);
                in = new BufferedInputStream(url.openStream());
            } else {
                in = new BufferedInputStream(new FileInputStream(name));
            }
            status = read(in);
        } catch (IOException e) {
            status = STATUS_OPEN_ERROR;
        }

        return status;
    }

    /**
     * Decodes LZW image data into pixel array.
     * Adapted from John Cristy's ImageMagick.
     */
    protected void decodeImageData() {
        int NullCode = -1;
        int npix = iw * ih;
        int available,
                clear,
                code_mask,
                code_size,
                end_of_information,
                in_code,
                old_code,
                bits,
                code,
                count,
                i,
                datum,
                data_size,
                first,
                top,
                bi,
                pi;

        if ((pixels == null) || (pixels.length < npix)) {
            pixels = new byte[npix]; // allocate new pixel array
        }
        if (prefix == null) prefix = new short[MaxStackSize];
        if (suffix == null) suffix = new byte[MaxStackSize];
        if (pixelStack == null) pixelStack = new byte[MaxStackSize + 1];

        //  Initialize GIF data stream decoder.

        data_size = read();
        clear = 1 << data_size;
        end_of_information = clear + 1;
        available = clear + 2;
        old_code = NullCode;
        code_size = data_size + 1;
        code_mask = (1 << code_size) - 1;
        for (code = 0; code < clear; code++) {
            prefix[code] = 0;
            suffix[code] = (byte) code;
        }

        //  Decode GIF pixel stream.

        datum = bits = count = first = top = pi = bi = 0;

        for (i = 0; i < npix; ) {
            if (top == 0) {
                if (bits < code_size) {
                    //  Load bytes until there are enough bits for a code.
                    if (count == 0) {
                        // Read a new data block.
                        count = readBlock();
                        if (count <= 0)
                            break;
                        bi = 0;
                    }
                    datum += (((int) block[bi]) & 0xff) << bits;
                    bits += 8;
                    bi++;
                    count--;
                    continue;
                }

                //  Get the next code.

                code = datum & code_mask;
                datum >>= code_size;
                bits -= code_size;

                //  Interpret the code

                if ((code > available) || (code == end_of_information))
                    break;
                if (code == clear) {
                    //  Reset decoder.
                    code_size = data_size + 1;
                    code_mask = (1 << code_size) - 1;
                    available = clear + 2;
                    old_code = NullCode;
                    continue;
                }
                if (old_code == NullCode) {
                    pixelStack[top++] = suffix[code];
                    old_code = code;
                    first = code;
                    continue;
                }
                in_code = code;
                if (code == available) {
                    pixelStack[top++] = (byte) first;
                    code = old_code;
                }
                while (code > clear) {
                    pixelStack[top++] = suffix[code];
                    code = prefix[code];
                }
                first = ((int) suffix[code]) & 0xff;

                //  Add a new string to the string table,

                if (available >= MaxStackSize)
                    break;
                pixelStack[top++] = (byte) first;
                prefix[available] = (short) old_code;
                suffix[available] = (byte) first;
                available++;
                if (((available & code_mask) == 0)
                        && (available < MaxStackSize)) {
                    code_size++;
                    code_mask += available;
                }
                old_code = in_code;
            }

            //  Pop a pixel off the pixel stack.

            top--;
            pixels[pi++] = pixelStack[top];
            i++;
        }

        for (i = pi; i < npix; i++) {
            pixels[i] = 0; // clear missing pixels
        }

    }

    /**
     * Returns true if an error was encountered during reading/decoding
     */
    protected boolean err() {
        return status != STATUS_OK;
    }

    /**
     * Initializes or re-initializes reader
     */
    protected void init() {
        status = STATUS_OK;
        frameCount = 0;
        frames = new ArrayList();
        gct = null;
        lct = null;
    }

    /**
     * Reads a single byte from the input stream.
     */
    protected int read() {
        int curByte = 0;
        try {
            curByte = in.read();
        } catch (IOException e) {
            status = STATUS_FORMAT_ERROR;
        }
        return curByte;
    }

    /**
     * Reads next variable length block from input.
     *
     * @return number of bytes stored in "buffer"
     */
    protected int readBlock() {
        blockSize = read();
        int n = 0;
        if (blockSize > 0) {
            try {
                int count = 0;
                while (n < blockSize) {
                    count = in.read(block, n, blockSize - n);
                    if (count == -1)
                        break;
                    n += count;
                }
            } catch (IOException e) {
            }

            if (n < blockSize) {
                status = STATUS_FORMAT_ERROR;
            }
        }
        return n;
    }

    /**
     * Reads color table as 256 RGB integer values
     *
     * @param ncolors int number of colors to read
     * @return int array containing 256 colors (packed ARGB with full alpha)
     */
    protected int[] readColorTable(int ncolors) {
        int nbytes = 3 * ncolors;
        int[] tab = null;
        byte[] c = new byte[nbytes];
        int n = 0;
        try {
            n = in.read(c);
        } catch (IOException e) {
        }
        if (n < nbytes) {
            status = STATUS_FORMAT_ERROR;
        } else {
            tab = new int[256]; // max size to avoid bounds checks
            int i = 0;
            int j = 0;
            while (i < ncolors) {
                int r = ((int) c[j++]) & 0xff;
                int g = ((int) c[j++]) & 0xff;
                int b = ((int) c[j++]) & 0xff;
                tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b;
            }
        }
        return tab;
    }

    /**
     * Main file parser.  Reads GIF content blocks.
     */
    protected void readContents() {
        // read GIF file content blocks
        boolean done = false;
        while (!(done || err())) {
            int code = read();
            switch (code) {

                case 0x2C: // image separator
                    readImage();
                    break;

                case 0x21: // extension
                    code = read();
                    switch (code) {
                        case 0xf9: // graphics control extension
                            readGraphicControlExt();
                            break;

                        case 0xff: // application extension
                            readBlock();
                            String app = "";
                            for (int i = 0; i < 11; i++) {
                                app += (char) block[i];
                            }
                            if (app.equals("NETSCAPE2.0")) {
                                readNetscapeExt();
                            } else
                                skip(); // don't care
                            break;

                        default: // uninteresting extension
                            skip();
                    }
                    break;

                case 0x3b: // terminator
                    done = true;
                    break;

                case 0x00: // bad byte, but keep going and see what happens
                    break;

                default:
                    status = STATUS_FORMAT_ERROR;
            }
        }
    }

    /**
     * Reads Graphics Control Extension values
     */
    protected void readGraphicControlExt() {
        read(); // block size
        int packed = read(); // packed fields
        dispose = (packed & 0x1c) >> 2; // disposal method
        if (dispose == 0) {
            dispose = 1; // elect to keep old image if discretionary
        }
        transparency = (packed & 1) != 0;
        delay = readShort() * 10; // delay in milliseconds
        transIndex = read(); // transparent color index
        read(); // block terminator
    }

    /**
     * Reads GIF file header information.
     */
    protected void readHeader() {
        String id = "";
        for (int i = 0; i < 6; i++) {
            id += (char) read();
        }
        if (!id.startsWith("GIF")) {
            status = STATUS_FORMAT_ERROR;
            return;
        }

        readLSD();
        if (gctFlag && !err()) {
            gct = readColorTable(gctSize);
            bgColor = gct[bgIndex];
        }
    }

    /**
     * Reads next frame image
     */
    protected void readImage() {
        ix = readShort(); // (sub)image position & size
        iy = readShort();
        iw = readShort();
        ih = readShort();

        int packed = read();
        lctFlag = (packed & 0x80) != 0; // 1 - local color table flag
        interlace = (packed & 0x40) != 0; // 2 - interlace flag
        // 3 - sort flag
        // 4-5 - reserved
        lctSize = 2 << (packed & 7); // 6-8 - local color table size

        if (lctFlag) {
            lct = readColorTable(lctSize); // read table
            act = lct; // make local table active
        } else {
            act = gct; // make global table active
            if (bgIndex == transIndex)
                bgColor = 0;
        }
        int save = 0;
        if (transparency) {
            save = act[transIndex];
            act[transIndex] = 0; // set transparent color if specified
        }

        if (act == null) {
            status = STATUS_FORMAT_ERROR; // no color table defined
        }

        if (err()) return;

        decodeImageData(); // decode pixel data
        skip();

        if (err()) return;

        frameCount++;

        // create new image to receive frame data
        image =
                new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB_PRE);

        setPixels(); // transfer pixel data to image

        frames.add(new GifFrame(image, delay)); // add image to frame list

        if (transparency) {
            act[transIndex] = save;
        }
        resetFrame();

    }

    /**
     * Reads Logical Screen Descriptor
     */
    protected void readLSD() {

        // logical screen size
        width = readShort();
        height = readShort();

        // packed fields
        int packed = read();
        gctFlag = (packed & 0x80) != 0; // 1   : global color table flag
        // 2-4 : color resolution
        // 5   : gct sort flag
        gctSize = 2 << (packed & 7); // 6-8 : gct size

        bgIndex = read(); // background color index
        pixelAspect = read(); // pixel aspect ratio
    }

    /**
     * Reads Netscape extenstion to obtain iteration count
     */
    protected void readNetscapeExt() {
        do {
            readBlock();
            if (block[0] == 1) {
                // loop count sub-block
                int b1 = ((int) block[1]) & 0xff;
                int b2 = ((int) block[2]) & 0xff;
                loopCount = (b2 << 8) | b1;
            }
        } while ((blockSize > 0) && !err());
    }

    /**
     * Reads next 16-bit value, LSB first
     */
    protected int readShort() {
        // read 16-bit value, LSB first
        return read() | (read() << 8);
    }

    /**
     * Resets frame state for reading next image.
     */
    protected void resetFrame() {
        lastDispose = dispose;
        lastRect = new Rectangle(ix, iy, iw, ih);
        lastImage = image;
        lastBgColor = bgColor;
        int dispose = 0;
        boolean transparency = false;
        int delay = 0;
        lct = null;
    }

    protected void skip() {
        do {
            readBlock();
        } while ((blockSize > 0) && !err());
    }
}

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.ImageWriter;
import javax.imageio.stream.ImageInputStream;
import javax.imageio.stream.ImageOutputStream;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.Iterator;

/**
 * Created by yinjd on 2018/3/7.
 */
public class ImageUtils {

    public enum IMAGE_FORMAT {
        BMP("bmp"),
        JPG("jpg"),
        WBMP("wbmp"),
        JPEG("jpeg"),
        PNG("png"),
        GIF("gif");

        private String value;

        IMAGE_FORMAT(String value) {
            this.value = value;
        }

        public String getValue() {
            return value;
        }

        public void setValue(String value) {
            this.value = value;
        }
    }

    /**
     * 获取文件名
     *
     * @param filePath 文件路径
     * @return 文件名
     * @throws IOException
     */
    public static String getFileName(String filePath) throws IOException {
        File file = new File(filePath);
        if (!file.exists()) {
            throw new IOException("file not exist!");
        }
        return file.getName();
    }

    /**
     * 获取图片格式
     *
     * @param file 图片文件
     * @return 图片格式
     */
    public static String getImageFormatName(File file) throws IOException {
        String formatName = null;
        ImageInputStream iis = ImageIO.createImageInputStream(file);
        Iterator<ImageReader> imageReader = ImageIO.getImageReaders(iis);
        if (imageReader.hasNext()) {
            ImageReader reader = imageReader.next();
            formatName = reader.getFormatName();
        }
        return formatName;
    }

    /**
     * 获取某个文件的前缀路径
     * <p>
     * 不包含文件名的路径
     *
     * @param file 当前文件对象
     * @return
     * @throws IOException
     */
    public static String getFilePrefixPath(File file) throws IOException {
        String path;
        if (!file.exists()) {
            throw new IOException("file not exist!");
        }
        String fileName = file.getName();
        path = file.getPath().replace(fileName, "");
        return path;
    }

    /**
     * 获取某个文件的前缀路径
     * <p>
     * 不包含文件名的路径
     *
     * @param path 当前文件路径
     * @return 不包含文件名的路径
     * @throws Exception
     */
    public static String getFilePrefixPath(String path) throws Exception {
        if (null == path || path.isEmpty()) {
            throw new Exception("文件路径为空！");
        }
        int index = path.lastIndexOf(File.separator);
        if (index > 0) {
            path = path.substring(0, index + 1);
        }
        return path;
    }

    /**
     * 获取不包含后缀的文件路径(包含.)
     *
     * @param src
     * @return
     */
    public static String getPathWithoutSuffix(String src) {
        String path = src;
        int index = path.lastIndexOf(".");
        if (index > 0) {
            path = path.substring(0, index + 1);
        }
        return path;
    }

    /**
     * 获取系统支持的图片格式
     */
    public static void getOSSupportsStandardImageFormat() {
        String[] readerFormatName = ImageIO.getReaderFormatNames();
        String[] readerSuffixName = ImageIO.getReaderFileSuffixes();
        String[] readerMIMEType = ImageIO.getReaderMIMETypes();
        System.out.println("========================= OS supports reader ========================");
        System.out.println("OS supports reader format name :  " + Arrays.asList(readerFormatName));
        System.out.println("OS supports reader suffix name :  " + Arrays.asList(readerSuffixName));
        System.out.println("OS supports reader MIME type :  " + Arrays.asList(readerMIMEType));

        String[] writerFormatName = ImageIO.getWriterFormatNames();
        String[] writerSuffixName = ImageIO.getWriterFileSuffixes();
        String[] writerMIMEType = ImageIO.getWriterMIMETypes();

        System.out.println("========================= OS supports writer ========================");
        System.out.println("OS supports writer format name :  " + Arrays.asList(writerFormatName));
        System.out.println("OS supports writer suffix name :  " + Arrays.asList(writerSuffixName));
        System.out.println("OS supports writer MIME type :  " + Arrays.asList(writerMIMEType));
    }

    /**
     * 剪切图片
     *
     * @param sourcePath     待剪切图片路径
     * @param targetPath 裁剪后保存路径（默认为源路径）
     * @param x          起始横坐标
     * @param y          起始纵坐标
     * @param width      剪切宽度
     * @param height     剪切高度
     * @throws IOException
     * @returns 裁剪后保存路径（图片后缀根据图片本身类型生成）
     */
    public static String cutImage(String sourcePath, String targetPath, int x, int y, int width, int height) throws IOException {
        File file = new File(sourcePath);
        if (!file.exists()) {
            throw new IOException("not found the image：" + sourcePath);
        }
        if (null == targetPath || targetPath.isEmpty()) {
            targetPath = sourcePath;
        }

        String formatName = getImageFormatName(file);
        if (null == formatName) {
            return targetPath;
        }
        formatName = formatName.toLowerCase();

        // 防止图片后缀与图片本身类型不一致的情况
        String pathPrefix = getPathWithoutSuffix(targetPath);
        targetPath = pathPrefix + formatName;

        // GIF需要特殊处理
        if (IMAGE_FORMAT.GIF.getValue() == formatName) {
            GifDecoder decoder = new GifDecoder();
            int status = decoder.read(sourcePath);
            if (status != GifDecoder.STATUS_OK) {
                throw new IOException("read image " + sourcePath + " error!");
            }

            AnimatedGifEncoder encoder = new AnimatedGifEncoder();
            encoder.start(targetPath);
            encoder.setRepeat(decoder.getLoopCount());
            for (int i = 0; i < decoder.getFrameCount(); i++) {
                encoder.setDelay(decoder.getDelay(i));
                BufferedImage childImage = decoder.getFrame(i);
                BufferedImage image = childImage.getSubimage(x, y, width, height);
                encoder.addFrame(image);
            }
            encoder.finish();
        } else {
            BufferedImage image = ImageIO.read(file);
            image = image.getSubimage(x, y, width, height);
            ImageIO.write(image, formatName, new File(targetPath));
        }
        return targetPath;
    }

    /**
     * 压缩图片
     *
     * @param sourcePath 待压缩的图片路径
     * @param targetPath 压缩后图片路径（默认为初始路径）
     * @param width      压缩宽度
     * @param height     压缩高度
     * @throws IOException
     * @returns 裁剪后保存路径（图片后缀根据图片本身类型生成）
     */
    public static String zoom(String sourcePath, String targetPath, int width, int height) throws IOException {
        File file = new File(sourcePath);
        if (!file.exists()) {
            throw new IOException("not found the image ：" + sourcePath);
        }
        if (null == targetPath || targetPath.isEmpty()) {
            targetPath = sourcePath;
        }
        String formatName = getImageFormatName(file);
        if (null == formatName) {
            return targetPath;
        }
        formatName = formatName.toLowerCase();

        // 防止图片后缀与图片本身类型不一致,所以重新组合拼接
        String pathPrefix = getPathWithoutSuffix(targetPath);
        targetPath = pathPrefix + formatName;

        // GIF需要特殊处理
        if (IMAGE_FORMAT.GIF.getValue() == formatName) {
            GifDecoder decoder = new GifDecoder();
            int status = decoder.read(sourcePath);
            if (status != GifDecoder.STATUS_OK) {
                throw new IOException("read image " + sourcePath + " error!");
            }

            AnimatedGifEncoder encoder = new AnimatedGifEncoder();
            encoder.start(targetPath);
            encoder.setRepeat(decoder.getLoopCount());
            for (int i = 0; i < decoder.getFrameCount(); i++) {
                encoder.setDelay(decoder.getDelay(i));
                BufferedImage image = zoom(decoder.getFrame(i), width, height);
                encoder.addFrame(image);
            }
            encoder.finish();
        } else {
            BufferedImage image = ImageIO.read(file);
            BufferedImage zoomImage = zoom(image, width, height);
            ImageIO.write(zoomImage, formatName, new File(targetPath));
        }
        return targetPath;
    }

    /**
     * 读取图片
     *
     * @param file 图片文件
     * @return 图片数据
     * @throws IOException
     */
    private static BufferedImage[] readerImage(File file) throws IOException {
        BufferedImage sourceImage = ImageIO.read(file);
        BufferedImage[] images = null;
        ImageInputStream iis = ImageIO.createImageInputStream(file);
        Iterator<ImageReader> imageReaders = ImageIO.getImageReaders(iis);
        if (imageReaders.hasNext()) {
            ImageReader reader = imageReaders.next();
            reader.setInput(iis);
            int imageNumber = reader.getNumImages(true);
            images = new BufferedImage[imageNumber];
            for (int i = 0; i < imageNumber; i++) {
                BufferedImage image = reader.read(i);
                if (sourceImage.getWidth() > image.getWidth() || sourceImage.getHeight() > image.getHeight()) {
                    image = zoom(image, sourceImage.getWidth(), sourceImage.getHeight());
                }
                images[i] = image;
            }
            reader.dispose();
            iis.close();
        }
        return images;
    }

    /**
     * 根据要求处理图片
     *
     * @param images 图片数组
     * @param x      横向起始位置
     * @param y      纵向起始位置
     * @param width  宽度
     * @param height 宽度
     * @return 处理后的图片数组
     * @throws Exception
     */
    private static BufferedImage[] processImage(BufferedImage[] images, int x, int y, int width, int height) throws Exception {
        if (null == images) {
            return images;
        }
        BufferedImage[] oldImages = images;
        images = new BufferedImage[images.length];
        for (int i = 0; i < oldImages.length; i++) {
            BufferedImage image = oldImages[i];
            images[i] = image.getSubimage(x, y, width, height);
        }
        return images;
    }

    /**
     * 写入处理后的图片到file
     * <p>
     * 图片后缀根据图片格式生成
     *
     * @param images     处理后的图片数据
     * @param formatName 图片格式
     * @param file       写入文件对象
     * @throws Exception
     */
    private static void writerImage(BufferedImage[] images, String formatName, File file) throws Exception {
        Iterator<ImageWriter> imageWriters = ImageIO.getImageWritersByFormatName(formatName);
        if (imageWriters.hasNext()) {
            ImageWriter writer = imageWriters.next();
            String fileName = file.getName();
            int index = fileName.lastIndexOf(".");
            if (index > 0) {
                fileName = fileName.substring(0, index + 1) + formatName;
            }
            String pathPrefix = getFilePrefixPath(file.getPath());
            File outFile = new File(pathPrefix + fileName);
            ImageOutputStream ios = ImageIO.createImageOutputStream(outFile);
            writer.setOutput(ios);

            if (writer.canWriteSequence()) {
                writer.prepareWriteSequence(null);
                for (int i = 0; i < images.length; i++) {
                    BufferedImage childImage = images[i];
                    IIOImage image = new IIOImage(childImage, null, null);
                    writer.writeToSequence(image, null);
                }
                writer.endWriteSequence();
            } else {
                for (int i = 0; i < images.length; i++) {
                    writer.write(images[i]);
                }
            }

            writer.dispose();
            ios.close();
        }
    }

    /**
     * 剪切格式图片
     * <p>
     * 基于JDK Image I/O解决方案
     *
     * @param sourceFile 待剪切图片文件对象
     * @param destFile   裁剪后保存文件对象
     * @param x          剪切横向起始位置
     * @param y          剪切纵向起始位置
     * @param width      剪切宽度
     * @param height     剪切宽度
     * @throws Exception
     */
    public static void cutImage(File sourceFile, File destFile, int x, int y, int width, int height) throws Exception {
        // 读取图片信息
        BufferedImage[] images = readerImage(sourceFile);
        // 处理图片
        images = processImage(images, x, y, width, height);
        // 获取文件后缀
        String formatName = getImageFormatName(sourceFile);
        destFile = new File(getPathWithoutSuffix(destFile.getPath()) + formatName);

        // 写入处理后的图片到文件
        writerImage(images, formatName, destFile);
    }

    /**
     * 压缩图片
     *
     * @param sourceImage 待压缩图片
     * @param width       压缩图片高度
     * @param height       压缩图片宽度
     */
    public static BufferedImage zoom(BufferedImage sourceImage, int width, int height) {
        Image image = sourceImage.getScaledInstance(width, height, Image.SCALE_SMOOTH);
        BufferedImage zoomImage = new BufferedImage(width, height, sourceImage.getType());
        Graphics gc = zoomImage.getGraphics();
        gc.setColor(Color.WHITE);
        gc.drawImage(image, 0, 0, null);
        return zoomImage;
    }

    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {

        try {
            String filePath = "/Users/*/Desktop/images/CC_src_1242x2208.gif";
            String prefixPath = "/Users/*/Desktop/images/dest/";
            String destPath;
            File ccFile = new File(filePath);
            if (!ccFile.exists()) {
                throw new IOException("not found the image ：" + filePath);
            }
            int loopCount = 500;
            long start = System.currentTimeMillis();

            for (int i = 0; i < loopCount; i++) {
                destPath = prefixPath + "CC_des_" + i + ".gif";
                zoom(filePath, destPath, 300, 600);
            }
            long end = System.currentTimeMillis();
            System.out.println("开始于" + start + ", 结束于" + end + ", 平均用时" + (end - start) / loopCount + "毫秒.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}