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Apache XML Graphics Commons is a library that consists of several reusable
components used by Apache Batik and Apache FOP. Many of these components
can easily be used separately outside the domains of SVG and XSL-FO.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id: TIFFLZWDecoder.java 1732018 2016-02-24 04:51:06Z gadams $ */
package org.apache.xmlgraphics.image.codec.tiff;
import org.apache.xmlgraphics.image.codec.util.PropertyUtil;
// CSOFF: InnerAssignment
// CSOFF: MultipleVariableDeclarations
// CSOFF: OneStatementPerLine
// CSOFF: OperatorWrap
// CSOFF: WhitespaceAround
/**
* A class for performing LZW decoding.
*/
public class TIFFLZWDecoder {
byte[][] stringTable;
byte[] data;
byte[] uncompData;
int tableIndex;
int bitsToGet = 9;
int bytePointer;
// int bitPointer;
int dstIndex;
int w;
int predictor;
int samplesPerPixel;
int nextData;
int nextBits;
int[] andTable = {
511,
1023,
2047,
4095
};
public TIFFLZWDecoder(int w, int predictor, int samplesPerPixel) {
this.w = w;
this.predictor = predictor;
this.samplesPerPixel = samplesPerPixel;
}
/**
* Method to decode LZW compressed data.
*
* @param data The compressed data.
* @param uncompData Array to return the uncompressed data in.
* @param h The number of rows the compressed data contains.
*/
public byte[] decode(byte[] data, byte[] uncompData, int h) {
if (data[0] == (byte)0x00 && data[1] == (byte)0x01) {
throw new UnsupportedOperationException(PropertyUtil.getString("TIFFLZWDecoder0"));
}
initializeStringTable();
this.data = data;
// this.h = h;
this.uncompData = uncompData;
// Initialize pointers
bytePointer = 0;
// bitPointer = 0;
dstIndex = 0;
nextData = 0;
nextBits = 0;
int code;
int oldCode = 0;
byte[] string;
while ((code = getNextCode()) != 257
&& dstIndex != uncompData.length) {
if (code == 256) {
initializeStringTable();
code = getNextCode();
if (code == 257) {
break;
}
writeString(stringTable[code]);
oldCode = code;
} else {
if (code < tableIndex) {
string = stringTable[code];
writeString(string);
addStringToTable(stringTable[oldCode], string[0]);
oldCode = code;
} else {
string = stringTable[oldCode];
string = composeString(string, string[0]);
writeString(string);
addStringToTable(string);
oldCode = code;
}
}
}
// Horizontal Differencing Predictor
if (predictor == 2) {
int count;
for (int j = 0; j < h; j++) {
count = samplesPerPixel * (j * w + 1);
for (int i = samplesPerPixel; i < w * samplesPerPixel; i++) {
uncompData[count] += uncompData[count - samplesPerPixel];
count++;
}
}
}
return uncompData;
}
/**
* Initialize the string table.
*/
public void initializeStringTable() {
stringTable = new byte[4096][];
for (int i = 0; i < 256; i++) {
stringTable[i] = new byte[1];
stringTable[i][0] = (byte)i;
}
tableIndex = 258;
bitsToGet = 9;
}
/**
* Write out the string just uncompressed.
*/
public void writeString(byte[] string) {
for (int i = 0; i < string.length; i++) {
uncompData[dstIndex++] = string[i];
}
}
/**
* Add a new string to the string table.
*/
public void addStringToTable(byte[] oldString, byte newString) {
int length = oldString.length;
byte[] string = new byte[length + 1];
System.arraycopy(oldString, 0, string, 0, length);
string[length] = newString;
// Add this new String to the table
stringTable[tableIndex++] = string;
if (tableIndex == 511) {
bitsToGet = 10;
} else if (tableIndex == 1023) {
bitsToGet = 11;
} else if (tableIndex == 2047) {
bitsToGet = 12;
}
}
/**
* Add a new string to the string table.
*/
public void addStringToTable(byte[] string) {
// Add this new String to the table
stringTable[tableIndex++] = string;
if (tableIndex == 511) {
bitsToGet = 10;
} else if (tableIndex == 1023) {
bitsToGet = 11;
} else if (tableIndex == 2047) {
bitsToGet = 12;
}
}
/**
* Append newString to the end of oldString.
*/
public byte[] composeString(byte[] oldString, byte newString) {
int length = oldString.length;
byte[] string = new byte[length + 1];
System.arraycopy(oldString, 0, string, 0, length);
string[length] = newString;
return string;
}
// Returns the next 9, 10, 11 or 12 bits
public int getNextCode() {
// Attempt to get the next code. The exception is caught to make
// this robust to cases wherein the EndOfInformation code has been
// omitted from a strip. Examples of such cases have been observed
// in practice.
try {
nextData = (nextData << 8) | (data[bytePointer++] & 0xff);
nextBits += 8;
if (nextBits < bitsToGet) {
nextData = (nextData << 8) | (data[bytePointer++] & 0xff);
nextBits += 8;
}
int code =
(nextData >> (nextBits - bitsToGet)) & andTable[bitsToGet - 9];
nextBits -= bitsToGet;
return code;
} catch (ArrayIndexOutOfBoundsException e) {
// Strip not terminated as expected: return EndOfInformation code.
return 257;
}
}
}