Class WriteGifEncoder

java.lang.Object
  |
  +--WriteGifEncoder

public class WriteGifEncoder

extends java.lang.Object

The WriteGifEncoder class writes out an Image object as a named GIF file. After creating the class, use writeFile() to actually write the file.

This module was taken from NIH ImageJ and was in turn derived from GifEncoder.java and MedianCut.java. It writes out an Image as a GIF file after convering 24-bit RGB to an 8-bit IndexColorModel. It was taken from a public domain version of Wayne Rasband's ImageJ source code available at http://rsb.info.nih.gov/nih-image/

 Transparency handling and variable bit size courtesy of Jack Palevich.

 Copyright (C) 1996 by Jef Poskanzer .  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 at http://www.acme.com/java/

This code was then modified by P. Lemkin, G. Thornwall, NCI/FCRDC.

This work was produced by Peter Lemkin of the National Cancer Institute, an agency of the United States Government. As a work of the United States Government there is no associated copyright. It is offered as open source software under the Mozilla Public License (version 1.1) subject to the limitations noted in the accompanying LEGAL file. This notice must be included with the code. The MAExplorer Mozilla and Legal files are available on http://maexplorer.sourceforge.net/.

Version:

$Date: 2002/10/14 20:44:22 $ $Revision: $

Author:

P. Lemkin (NCI), G. Thornwall (SAIC), NCI-Frederick, Frederick, MD

See Also:

MAExplorer Home

Field Summary

private int	a_count
private byte[]	accum
private byte[]	b
private static int	BITS
private boolean	clear_flg 80% occupancy
private int	ClearCode
private int[]	codetab
private int	cur_accum
private int	cur_bits
private static int	EOF
private int	EOFCode
private int	free_ent
private byte[]	g
private int	g_init_bits
private int	height
private int	Height
private int	hsize
private static int	HSIZE
private int[]	htab
private java.awt.Image	img Image if specified
private boolean	interlace 80% occupancy
private boolean	Interlace 80% occupancy
private int[]	masks
private int	maxbits
private int	maxcode
private int	maxmaxcode
private int	n_bits
private int	numPixels
private boolean	ok 80% occupancy
private int	pixelIndex
private byte[]	pixels
private byte[]	r
private int	width
private int	Width

Constructor Summary

WriteGifEncoder(java.awt.Image img)
WriteGifEncoder() - Constructs using 24-bit Image.

WriteGifEncoder(int width, int height, byte[] pixels, byte[] r, byte[] g, byte[] b)
WriteGifEncoder() - Constructs a new WriteGifEncoder.

Method Summary

private void	char_init() char_init() - Set up the 'byte output' routine
(package private) void	char_out(byte c, java.io.FileOutputStream outs) char_out() - add char to end of current packet, and if it is 254 characters, flush the packet to disk.
private void	cl_block(java.io.FileOutputStream outs) cl_block() - table clear for block compress Clear out the hash table.
private void	cl_hash(int hsize) cl_hash() - reset code table
private void	compress(int init_bits, java.io.FileOutputStream outs) compress() - GIF Image compression - modified 'compress'.
(package private) void	flush_char(java.io.FileOutputStream outs) flush_char() - flush packet to disk, and reset the accumulator
private void	GIFEncode(java.io.FileOutputStream outs, int Width, int Height, boolean Interlace, byte Background, int Transparent, int BitsPerPixel, byte[] Red, byte[] Green, byte[] Blue) GIFEncode() - encode the image Adapted from ppmtogif, which is based on GIFENCOD by David Rowley .
private int	GIFNextPixel() GIFNextPixel() - Return the next pixel from the image
private int	MAXCODE(int n_bits) MAXCODE() - return n bits
private void	output(int code, java.io.FileOutputStream outs) output() - Output the given code.
private void	Putbyte(byte b, java.io.FileOutputStream outs) Putbyte() - Write out a byte to the GIF file
private void	Putword(int w, java.io.FileOutputStream outs) Putword() - Write out a word to the GIF file
boolean	writeFile(java.lang.String oGifFileName) writeFile() - write the Gif encoded image to output file
private void	writeGif(java.io.FileOutputStream out) writeGif() - Saves the image as a GIF file.
private static void	writeString(java.io.FileOutputStream out, java.lang.String str) writeString() - write string to the file.

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait

Field Detail

EOF

private static final int EOF

BITS

private static final int BITS

HSIZE

private static final int HSIZE

ok

private boolean ok

80% occupancy

interlace

private boolean interlace

80% occupancy

Interlace

private boolean Interlace

80% occupancy

clear_flg

private boolean clear_flg

80% occupancy

htab

private int[] htab

codetab

private int[] codetab

a_count

private int a_count

hsize

private int hsize

free_ent

private int free_ent

g_init_bits

private int g_init_bits

ClearCode

private int ClearCode

EOFCode

private int EOFCode

width

private int width

height

private int height

Width

private int Width

Height

private int Height

pixelIndex

private int pixelIndex

numPixels

private int numPixels

n_bits

private int n_bits

maxbits

private int maxbits

maxcode

private int maxcode

maxmaxcode

private int maxmaxcode

cur_accum

private int cur_accum

cur_bits

private int cur_bits

img

private java.awt.Image img

Image if specified

masks

private int[] masks

accum

private byte[] accum

pixels

private byte[] pixels

r

private byte[] r

g

private byte[] g

b

private byte[] b

Constructor Detail

WriteGifEncoder

public WriteGifEncoder(int width,
                       int height,
                       byte[] pixels,
                       byte[] r,
                       byte[] g,
                       byte[] b)

WriteGifEncoder() - Constructs a new WriteGifEncoder. After creating the class, use writeFile() to actually write the file.

Parameters:

width - The image width.

height - The image height.

pixels - The pixel data.

r - The red look-up table.

g - The green look-up table.

b - The blue look-up table. [Not used in MAExplorer]

WriteGifEncoder

public WriteGifEncoder(java.awt.Image img)

WriteGifEncoder() - Constructs using 24-bit Image. After creating the class, use writeFile() to actually write the file. The image is assumed to be fully loaded. It converts the 24-bit image into an 8-bit image with (r,g,b)LUT[] data using the MedianCut algorithm.

Parameters:

img - is the RGB image

Method Detail

writeFile

public boolean writeFile(java.lang.String oGifFileName)

writeFile() - write the Gif encoded image to output file

Parameters:

oGifFileName - is full path of file name to be written

Returns:

true if succeed

writeGif

private void writeGif(java.io.FileOutputStream out)
               throws java.io.IOException

writeGif() - Saves the image as a GIF file.

Parameters:

out - is file output stream

writeString

private static void writeString(java.io.FileOutputStream out,
                                java.lang.String str)
                         throws java.io.IOException

writeString() - write string to the file.

Parameters:

out - is file output stream

str - is string to write

GIFEncode

private void GIFEncode(java.io.FileOutputStream outs,
                       int Width,
                       int Height,
                       boolean Interlace,
                       byte Background,
                       int Transparent,
                       int BitsPerPixel,
                       byte[] Red,
                       byte[] Green,
                       byte[] Blue)
                throws java.io.IOException

GIFEncode() - encode the image Adapted from ppmtogif, which is based on GIFENCOD by David Rowley . Lempel-Zim compression based on "compress".

Parameters:

outs - is file output stream

Width - of image

Height - of image

Interlace - flag

Background - value

Transparent - flag

BitsPerPixel - bits per pixel

Red - is byte array of data

Green - byte array of data

Blue - is byte array of data

GIFNextPixel

private int GIFNextPixel()
                  throws java.io.IOException

GIFNextPixel() - Return the next pixel from the image

Putword

private void Putword(int w,
                     java.io.FileOutputStream outs)
              throws java.io.IOException

Putword() - Write out a word to the GIF file

Putbyte

private void Putbyte(byte b,
                     java.io.FileOutputStream outs)
              throws java.io.IOException

Putbyte() - Write out a byte to the GIF file

MAXCODE

private final int MAXCODE(int n_bits)

MAXCODE() - return n bits

compress

private void compress(int init_bits,
                      java.io.FileOutputStream outs)
               throws java.io.IOException

compress() - GIF Image compression - modified 'compress'. Original code from GIFCOMPR.C GIF Image compression routines. * Lempel-Ziv compression based on 'compress'. GIF modifications by David Rowley (mgardi@watdcsu.waterloo.edu) This GIF Image compression - modified 'compress' was 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) 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 THE OLD implementation to ames!jaw. Block compression parameters -- after all codes are used up, and compression rate changes, start over.

output

private void output(int code,
                    java.io.FileOutputStream outs)
             throws java.io.IOException

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.

cl_block

private void cl_block(java.io.FileOutputStream outs)
               throws java.io.IOException

cl_block() - table clear for block compress Clear out the hash table.

cl_hash

private void cl_hash(int hsize)

cl_hash() - reset code table

char_init

private void char_init()

char_init() - Set up the 'byte output' routine

char_out

void char_out(byte c,
              java.io.FileOutputStream outs)
        throws java.io.IOException

char_out() - add char to end of current packet, and if it is 254 characters, flush the packet to disk.

flush_char

void flush_char(java.io.FileOutputStream outs)
          throws java.io.IOException

flush_char() - flush packet to disk, and reset the accumulator