Gif Encoder - writes out an image as a GIF. : GIF « 2D Graphics GUI « Java






Gif Encoder - writes out an image as a GIF.

 


import java.awt.Image;
import java.awt.image.ColorModel;
import java.awt.image.IndexColorModel;
import java.awt.image.PixelGrabber;
import java.io.IOException;
import java.io.OutputStream;


/**  GifEncoder - writes out an image as a GIF.
 *
 * Transparency handling and variable bit size courtesy of Jack Palevich.
 *
 * Copyright (C) 1996 by Jef Poskanzer <jef@acme.com>.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Visit the ACME Labs Java page for up-to-date versions of this and other
 * fine Java utilities: http://www.acme.com/java/
 */

public class GifEncoder {

  private boolean interlace = false;

  private int width, height;

  private byte[] pixels;

  private byte[] r, g, b; // the color look-up table

  private int pixelIndex;

  private int numPixels;

  private int transparentPixel = -1; // hpm

  /**
   *  Constructs a new GifEncoder. 
   * @param width The image width.
   * @param height  The image height.
   * @param pixels  The pixel data.
   * @param r   The red look-up table.
   * @param g   The green look-up table.
   * @param b   The blue look-up table.
   */
  public GifEncoder(int width, int height, byte[] pixels, byte[] r, byte[] g, byte[] b) {
    this.width = width;
    this.height = height;
    this.pixels = pixels;
    this.r = r;
    this.g = g;
    this.b = b;
    interlace = false;
    pixelIndex = 0;
    numPixels = width * height;
  }

  /** Constructs a new GifEncoder using an 8-bit AWT Image.
   The image is assumed to be fully loaded. */
  public GifEncoder(Image img) {
    width = img.getWidth(null);
    height = img.getHeight(null);
    pixels = new byte[width * height];
    PixelGrabber pg = new PixelGrabber(img, 0, 0, width, height, false);
    try {
      pg.grabPixels();
    } catch (InterruptedException e) {
      System.err.println(e);
    }
    ColorModel cm = pg.getColorModel();
    if (cm instanceof IndexColorModel) {
      pixels = (byte[]) (pg.getPixels());
      // hpm
      IndexColorModel icm = (IndexColorModel) cm;
      setTransparentPixel(icm.getTransparentPixel());
    } else
      throw new IllegalArgumentException("IMAGE_ERROR");
    IndexColorModel m = (IndexColorModel) cm;
    int mapSize = m.getMapSize();
    r = new byte[mapSize];
    g = new byte[mapSize];
    b = new byte[mapSize];
    m.getReds(r);
    m.getGreens(g);
    m.getBlues(b);
    interlace = false;
    pixelIndex = 0;
    numPixels = width * height;
  }

  /** Saves the image as a GIF file. */
  public void write(OutputStream out) throws IOException {
    // Figure out how many bits to use.
    int numColors = r.length;
    int BitsPerPixel;
    if (numColors <= 2)
      BitsPerPixel = 1;
    else if (numColors <= 4)
      BitsPerPixel = 2;
    else if (numColors <= 16)
      BitsPerPixel = 4;
    else
      BitsPerPixel = 8;

    int ColorMapSize = 1 << BitsPerPixel;
    byte[] reds = new byte[ColorMapSize];
    byte[] grns = new byte[ColorMapSize];
    byte[] blus = new byte[ColorMapSize];
    for (int i = 0; i < numColors; i++) {
      reds[i] = r[i];
      grns[i] = g[i];
      blus[i] = b[i];
    }

    // hpm
    GIFEncode(out, width, height, interlace, (byte) 0, getTransparentPixel(), BitsPerPixel, reds, grns, blus);
  }

  // hpm
  public void setTransparentPixel(int pixel) {
    transparentPixel = pixel;
  }

  // hpm
  public int getTransparentPixel() {
    return transparentPixel;
  }

  static void writeString(OutputStream out, String str) throws IOException {
    byte[] buf = str.getBytes();
    out.write(buf);
  }

  // Adapted from ppmtogif, which is based on GIFENCOD by David
  // Rowley <mgardi@watdscu.waterloo.edu>.  Lempel-Zim compression
  // based on "compress".

  int Width, Height;

  boolean Interlace;

  void GIFEncode(OutputStream outs, int Width, int Height, boolean Interlace,
      byte Background, int Transparent, int BitsPerPixel, byte[] Red,
      byte[] Green, byte[] Blue) throws IOException {
    byte B;
    int LeftOfs, TopOfs;
    int ColorMapSize;
    int InitCodeSize;
    int i;

    this.Width = Width;
    this.Height = Height;
    this.Interlace = Interlace;
    ColorMapSize = 1 << BitsPerPixel;
    LeftOfs = TopOfs = 0;

    // The initial code size
    if (BitsPerPixel <= 1)
      InitCodeSize = 2;
    else
      InitCodeSize = BitsPerPixel;

    // Write the Magic header
    writeString(outs, "GIF89a");

    // Write out the screen width and height
    Putword(Width, outs);
    Putword(Height, outs);

    // Indicate that there is a global colour map
    B = (byte) 0x80; // Yes, there is a color map
    // OR in the resolution
    B |= (byte) ((8 - 1) << 4);
    // Not sorted
    // OR in the Bits per Pixel
    B |= (byte) ((BitsPerPixel - 1));

    // Write it out
    Putbyte(B, outs);

    // Write out the Background colour
    Putbyte(Background, outs);

    // Pixel aspect ratio - 1:1.
    //Putbyte( (byte) 49, outs );
    // Java's GIF reader currently has a bug, if the aspect ratio byte is
    // not zero it throws an ImageFormatException.  It doesn't know that
    // 49 means a 1:1 aspect ratio.  Well, whatever, zero works with all
    // the other decoders I've tried so it probably doesn't hurt.
    Putbyte((byte) 0, outs);

    // Write out the Global Colour Map
    for (i = 0; i < ColorMapSize; ++i) {
      Putbyte(Red[i], outs);
      Putbyte(Green[i], outs);
      Putbyte(Blue[i], outs);
    }

    // Write out extension for transparent colour index, if necessary.
    if (Transparent != -1) {
      Putbyte((byte) '!', outs);
      Putbyte((byte) 0xf9, outs);
      Putbyte((byte) 4, outs);
      Putbyte((byte) 1, outs);
      Putbyte((byte) 0, outs);
      Putbyte((byte) 0, outs);
      Putbyte((byte) Transparent, outs);
      Putbyte((byte) 0, outs);
    }

    // Write an Image separator
    Putbyte((byte) ',', outs);

    // Write the Image header
    Putword(LeftOfs, outs);
    Putword(TopOfs, outs);
    Putword(Width, outs);
    Putword(Height, outs);

    // Write out whether or not the image is interlaced
    if (Interlace)
      Putbyte((byte) 0x40, outs);
    else
      Putbyte((byte) 0x00, outs);

    // Write out the initial code size
    Putbyte((byte) InitCodeSize, outs);

    // Go and actually compress the data
    compress(InitCodeSize + 1, outs);

    // Write out a Zero-length packet (to end the series)
    Putbyte((byte) 0, outs);

    // Write the GIF file terminator
    Putbyte((byte) ';', outs);
  }

  static final int EOF = -1;

  // Return the next pixel from the image
  int GIFNextPixel() throws IOException {
    if (pixelIndex == numPixels)
      return EOF;
    else
      return ((byte[]) pixels)[pixelIndex++] & 0xff;
  }

  // Write out a word to the GIF file
  void Putword(int w, OutputStream outs) throws IOException {
    Putbyte((byte) (w & 0xff), outs);
    Putbyte((byte) ((w >> 8) & 0xff), outs);
  }

  // Write out a byte to the GIF file
  void Putbyte(byte b, OutputStream outs) throws IOException {
    outs.write(b);
  }

  // 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

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

  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;

  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;

    char_init();

    ent = GIFNextPixel();

    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 = GIFNextPixel()) != 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);
  }

  // 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 };

  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);
    }
  }

  // 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;
  }

  // GIF Specific routines

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

  // Set up the 'byte output' routine
  void char_init() {
    a_count = 0;
  }

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

  // 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);
  }

  // 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;
    }
  }

}

class GifEncoderHashitem {
  public int rgb;
  public int count;
  public int index;
  public boolean isTransparent;

  public GifEncoderHashitem(int rgb, int count, int index,
      boolean isTransparent) {
    this.rgb = rgb;
    this.count = count;
    this.index = index;
    this.isTransparent = isTransparent;
  }

}

   
  








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