GifEncoder.java

import java.io.IOException;
import java.io.OutputStream;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Paint;

public class AnimatedGifEncoder {

	  protected int width; // image size

	  protected int height;
	  
	  protected int x = 0;
	  
	  protected int y = 0;

	  protected int transparent = -1; // 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 Bitmap 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 = ms / 10;
	  }

	  /**
	   * 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(int 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(Bitmap im) {
	    if ((im == null) || !started) {
	      return false;
	    }
	    boolean ok = true;
	    try {
	      if (!sizeSet) {
	        // use first frame's size
	        setSize(im.getWidth(), im.getHeight());
	      }
	      if(image != null) {
	      	// recycle the old Bitmap instance to free its memory
	      	image.recycle();
	      }
	      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 = (int)(100 / 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) {
	    width = w;
	    height = h;
	    if (width < 1)
	      width = 320;
	    if (height < 1)
	      height = 240;
	    sizeSet = true;
	  }
	  
	  /**
	   * Sets the GIF frame position. The position is 0,0 by default.
	   * Useful for only updating a section of the image
	   * 
	   * @param w
	   *          int frame width.
	   * @param h
	   *          int frame width.
	   */
	  public void setPosition(int x, int y) {
		 this.x = x;
		 this.y = y;
	  }

	  /**
	   * 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;
	  }

	  /**
	   * 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 != -1) {
	      transIndex = findClosest(transparent);
	    }
	  }

	  /**
	   * Returns index of palette color closest to c
	   * 
	   */
	  protected int findClosest(int c) {
	    if (colorTab == null)
	      return -1;
	    int r = (c >> 16) & 0xff;
	    int g = (c >> 8) & 0xff;
	    int b = (c >> 0) & 0xff;
	    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();
	    if ((w != width) || (h != height)) {
	      // create new image with right size/format
	      Bitmap temp = Bitmap.createBitmap(width, height, Config.RGB_565);
	      Canvas g = new Canvas(temp);
	      g.drawBitmap(image, 0, 0, new Paint());
	      image = temp;
	    }
	    int[] data = getImageData(image);
		pixels = new byte[data.length * 3];
		for (int i = 0; i < data.length; i++) {
			int td = data[i];
			int tind = i * 3;
			pixels[tind++] = (byte) ((td >> 0) & 0xFF);
			pixels[tind++] = (byte) ((td >> 8) & 0xFF);
			pixels[tind] = (byte) ((td >> 16) & 0xFF);
		}
	  }
	  protected int[] getImageData(Bitmap img) {
			int w = img.getWidth();
			int h = img.getHeight();

			int[] data = new int[w * h];
			img.getPixels(data, 0, w, 0, 0, w, h);
			return data;
		}

	  /**
	   * 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 == -1) {
	      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(x); // image position x,y = 0,0
	    writeShort(y);
	    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;

	    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);
	    }
	  }
	}