/* * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */package com.sun.imageio.plugins.common;import java.io.IOException;import java.io.PrintStream;import javax.imageio.stream.ImageOutputStream;/* * Modified from original LZWCompressor to change interface to passing a * buffer of data to be compressed. */public class LZWCompressor { /** base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF **/ int codeSize; /** reserved clear code based on code size **/ int clearCode; /** reserved end of data code based on code size **/ int endOfInfo; /** current number bits output for each code **/ int numBits; /** limit at which current number of bits code size has to be increased **/ int limit; /** the prefix code which represents the predecessor string to current input point **/ short prefix; /** output destination for bit codes **/ BitFile bf; /** general purpose LZW string table **/ LZWStringTable lzss; /** modify the limits of the code values in LZW encoding due to TIFF bug / feature **/ boolean tiffFudge; /** * @param out destination for compressed data * @param codeSize the initial code size for the LZW compressor * @param TIFF flag indicating that TIFF lzw fudge needs to be applied * @exception IOException if underlying output stream error **/ public LZWCompressor(ImageOutputStream out, int codeSize, boolean TIFF) throws IOException { bf = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff this.codeSize = codeSize; tiffFudge = TIFF; clearCode = 1 << codeSize; endOfInfo = clearCode + 1; numBits = codeSize + 1; limit = (1 << numBits) - 1; if (tiffFudge) { --limit; } prefix = (short)0xFFFF; lzss = new LZWStringTable(); lzss.clearTable(codeSize); bf.writeBits(clearCode, numBits); } /** * @param buf data to be compressed to output stream * @exception IOException if underlying output stream error **/ public void compress(byte[] buf, int offset, int length) throws IOException { int idx; byte c; short index; int maxOffset = offset + length; for (idx = offset; idx < maxOffset; ++idx) { c = buf[idx]; if ((index = lzss.findCharString(prefix, c)) != -1) { prefix = index; } else { bf.writeBits(prefix, numBits); if (lzss.addCharString(prefix, c) > limit) { if (numBits == 12) { bf.writeBits(clearCode, numBits); lzss.clearTable(codeSize); numBits = codeSize + 1; } else { ++numBits; } limit = (1 << numBits) - 1; if (tiffFudge) { --limit; } } prefix = (short)((short)c & 0xFF); } } } /* * Indicate to compressor that no more data to go so write out * any remaining buffered data. * * @exception IOException if underlying output stream error */ public void flush() throws IOException { if (prefix != -1) { bf.writeBits(prefix, numBits); } bf.writeBits(endOfInfo, numBits); bf.flush(); } public void dump(PrintStream out) { lzss.dump(out); }}
/*
* Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.imageio.plugins.common;
import java.io.IOException;
import java.io.PrintStream;
import javax.imageio.stream.ImageOutputStream;
/*
* Modified from original LZWCompressor to change interface to passing a
* buffer of data to be compressed.
*/
public class LZWCompressor {
/** base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF **/
int codeSize;
/** reserved clear code based on code size **/
int clearCode;
/** reserved end of data code based on code size **/
int endOfInfo;
/** current number bits output for each code **/
int numBits;
/** limit at which current number of bits code size has to be increased **/
int limit;
/** the prefix code which represents the predecessor string to current input point **/
short prefix;
/** output destination for bit codes **/
BitFile bf;
/** general purpose LZW string table **/
LZWStringTable lzss;
/** modify the limits of the code values in LZW encoding due to TIFF bug / feature **/
boolean tiffFudge;
/**
* @param out destination for compressed data
* @param codeSize the initial code size for the LZW compressor
* @param TIFF flag indicating that TIFF lzw fudge needs to be applied
* @exception IOException if underlying output stream error
**/
public LZWCompressor(ImageOutputStream out, int codeSize, boolean TIFF)
throws IOException
{
bf = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff
this.codeSize = codeSize;
tiffFudge = TIFF;
clearCode = 1 << codeSize;
endOfInfo = clearCode + 1;
numBits = codeSize + 1;
limit = (1 << numBits) - 1;
if (tiffFudge) {
--limit;
}
prefix = (short)0xFFFF;
lzss = new LZWStringTable();
lzss.clearTable(codeSize);
bf.writeBits(clearCode, numBits);
}
/**
* @param buf data to be compressed to output stream
* @exception IOException if underlying output stream error
**/
public void compress(byte[] buf, int offset, int length)
throws IOException
{
int idx;
byte c;
short index;
int maxOffset = offset + length;
for (idx = offset; idx < maxOffset; ++idx) {
c = buf[idx];
if ((index = lzss.findCharString(prefix, c)) != -1) {
prefix = index;
} else {
bf.writeBits(prefix, numBits);
if (lzss.addCharString(prefix, c) > limit) {
if (numBits == 12) {
bf.writeBits(clearCode, numBits);
lzss.clearTable(codeSize);
numBits = codeSize + 1;
} else {
++numBits;
}
limit = (1 << numBits) - 1;
if (tiffFudge) {
--limit;
}
}
prefix = (short)((short)c & 0xFF);
}
}
}
/*
* Indicate to compressor that no more data to go so write out
* any remaining buffered data.
*
* @exception IOException if underlying output stream error
*/
public void flush() throws IOException {
if (prefix != -1) {
bf.writeBits(prefix, numBits);
}
bf.writeBits(endOfInfo, numBits);
bf.flush();
}
public void dump(PrintStream out) {
lzss.dump(out);
}
}