using System;
/*
* Copyright (c) 2001 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* -Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduct the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY
* IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
* NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE
* LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
* OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS
* LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT,
* INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
* CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF
* OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that Software is not designed,licensed or intended for use in
* the design, construction, operation or maintenance of any nuclear facility.
*/
namespace iTextSharp.text.pdf.codec {
/**
* A class for performing LZW decoding.
*
*
*/
public class TIFFLZWDecoder {
byte[][] stringTable;
byte[] data = null;
byte[] uncompData;
int tableIndex, bitsToGet = 9;
int bytePointer;
int dstIndex;
int w, h;
int predictor, samplesPerPixel;
int nextData = 0;
int nextBits = 0;
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 InvalidOperationException("TIFF 5.0-style LZW codes are not supported.");
}
InitializeStringTable();
this.data = data;
this.h = h;
this.uncompData = uncompData;
// Initialize pointers
bytePointer = 0;
dstIndex = 0;
nextData = 0;
nextBits = 0;
int code, oldCode = 0;
byte[] strn;
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) {
strn = stringTable[code];
WriteString(strn);
AddStringToTable(stringTable[oldCode], strn[0]);
oldCode = code;
} else {
strn = stringTable[oldCode];
strn = ComposeString(strn, strn[0]);
WriteString(strn);
AddStringToTable(strn);
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[] strn) {
// Fix for broken tiff files
int max = uncompData.Length - dstIndex;
if (strn.Length < max)
max = strn.Length;
System.Array.Copy(strn, 0, uncompData, dstIndex, max);
dstIndex += max;
}
/**
* Add a new string to the string table.
*/
public void AddStringToTable(byte[] oldString, byte newString) {
int length = oldString.Length;
byte[] strn = new byte[length + 1];
Array.Copy(oldString, 0, strn, 0, length);
strn[length] = newString;
// Add this new String to the table
stringTable[tableIndex++] = strn;
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[] strn) {
// Add this new String to the table
stringTable[tableIndex++] = strn;
if (tableIndex == 511) {
bitsToGet = 10;
} else if (tableIndex == 1023) {
bitsToGet = 11;
} else if (tableIndex == 2047) {
bitsToGet = 12;
}
}
/**
* Append <code>newString</code> to the end of <code>oldString</code>.
*/
public byte[] ComposeString(byte[] oldString, byte newString) {
int length = oldString.Length;
byte[] strn = new byte[length + 1];
Array.Copy(oldString, 0, strn, 0, length);
strn[length] = newString;
return strn;
}
// 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 (IndexOutOfRangeException) {
// Strip not terminated as expected: return EndOfInformation code.
return 257;
}
}
}
}
Submit an article or tip