Mega Code Archive
Gif Encoder - writes out an image as a GIF
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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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