PDFFilters.py

#
# peepdf is a tool to analyse and modify PDF files
#    http://peepdf.eternal-todo.com
#    By Jose Miguel Esparza <jesparza AT eternal-todo.com>
#
#    Copyright (C) 2011-2017 Jose Miguel Esparza
#
#    This file is part of peepdf.
#
#        peepdf is free software: you can redistribute it and/or modify
#        it under the terms of the GNU General Public License as published by
#        the Free Software Foundation, either version 3 of the License, or
#        (at your option) any later version.
#
#        peepdf 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 for more details.
#
#        You should have received a copy of the GNU General Public License
#        along with peepdf.    If not, see <http://www.gnu.org/licenses/>.
#

# Some code has been reused and modified from the original by Mathieu Fenniak:
# Parameters management in Flate and LZW algorithms, asciiHexDecode and ascii85Decode
#
# Copyright (c) 2006, Mathieu Fenniak
# 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.
# * 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.
# * The name of the author may not be used to endorse or promote products
# derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.


'''
    Module to manage encoding/decoding in PDF files
'''

import sys, zlib, lzw, struct
from PDFUtils import getNumsFromBytes, getBytesFromBits, getBitsFromNum
from ccitt import CCITTFax


def decodeStream(stream, filter, parameters={}):
    '''
        Decode the given stream
        
        @param stream: Stream to be decoded (string)
        @param filter: Filter to apply to decode the stream
        @param parameters: List of PDFObjects containing the parameters for the filter
        @return: A tuple (status,statusContent), where statusContent is the decoded stream in case status = 0 or an error in case status = -1
    '''
    if filter == '/ASCIIHexDecode' or filter == '/AHx':
        ret = asciiHexDecode(stream)
    elif filter == '/ASCII85Decode' or filter == '/A85':
        ret = ascii85Decode(stream)
    elif filter == '/LZWDecode' or filter == '/LZW':
        ret = lzwDecode(stream, parameters)
    elif filter == '/FlateDecode' or filter == '/Fl':
        ret = flateDecode(stream, parameters)
    elif filter == '/RunLengthDecode' or filter == '/RL':
        ret = runLengthDecode(stream)
    elif filter == '/CCITTFaxDecode' or filter == '/CCF':
        ret = ccittFaxDecode(stream, parameters)
    elif filter == '/JBIG2Decode':
        ret = jbig2Decode(stream, parameters)
    elif filter == '/DCTDecode' or filter == '/DCT':
        ret = dctDecode(stream, parameters)
    elif filter == '/JPXDecode':
        ret = jpxDecode(stream)
    elif filter == '/Crypt':
        ret = crypt(stream, parameters)
    else:
        ret = (-1, 'Unknown filter "%s"' % filter)
    return ret


def encodeStream(stream, filter, parameters={}):
    '''
        Encode the given stream
        
        @param stream: Stream to be decoded (string)
        @param filter: Filter to apply to decode the stream
        @param parameters: List of PDFObjects containing the parameters for the filter
        @return: A tuple (status,statusContent), where statusContent is the encoded stream in case status = 0 or an error in case status = -1
    '''
    if filter == '/ASCIIHexDecode':
        ret = asciiHexEncode(stream)
    elif filter == '/ASCII85Decode':
        ret = ascii85Encode(stream)
    elif filter == '/LZWDecode':
        ret = lzwEncode(stream, parameters)
    elif filter == '/FlateDecode':
        ret = flateEncode(stream, parameters)
    elif filter == '/RunLengthDecode':
        ret = runLengthEncode(stream)
    elif filter == '/CCITTFaxDecode':
        ret = ccittFaxEncode(stream, parameters)
    elif filter == '/JBIG2Decode':
        ret = jbig2Encode(stream, parameters)
    elif filter == '/DCTDecode':
        ret = dctEncode(stream, parameters)
    elif filter == '/JPXDecode':
        ret = jpxEncode(stream)
    elif filter == '/Crypt':
        ret = crypt(stream, parameters)
    else:
        ret = (-1, 'Unknown filter "%s"' % filter)
    return ret


'''
The ascii85Decode code is part of pdfminer (http://pypi.python.org/pypi/pdfminer/)

Copyright (c) 2004-2010 Yusuke Shinyama <yusuke at cs dot nyu dot edu>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 

    """
    In ASCII85 encoding, every four bytes are encoded with five ASCII
    letters, using 85 different types of characters (as 256**4 < 85**5).
    When the length of the original bytes is not a multiple of 4, a special
    rule is used for round up.
    
    The Adobe's ASCII85 implementation is slightly different from
    its original in handling the last characters.
    
    The sample string is taken from:
      http://en.wikipedia.org/w/index.php?title=Ascii85
    
    >>> ascii85decode('9jqo^BlbD-BleB1DJ+*+F(f,q')
    'Man is distinguished'
    >>> ascii85decode('E,9)oF*2M7/c~>')
    'pleasure.'
    """

'''


def ascii85Decode(stream):
    '''
        Method to decode streams using ASCII85
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    n = b = 0
    decodedStream = ''
    try:
        for c in stream:
            if '!' <= c and c <= 'u':
                n += 1
                b = b * 85 + (ord(c) - 33)
                if n == 5:
                    decodedStream += struct.pack('>L', b)
                    n = b = 0
            elif c == 'z':
                assert n == 0
                decodedStream += '\0\0\0\0'
            elif c == '~':
                if n:
                    for _ in range(5 - n):
                        b = b * 85 + 84
                    decodedStream += struct.pack('>L', b)[:n - 1]
                break
    except:
        return (-1, 'Unspecified error')
    return (0, decodedStream)


def ascii85Encode(stream):
    '''
        Method to encode streams using ASCII85 (NOT SUPPORTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    return (-1, 'Ascii85Encode not supported yet')


def asciiHexDecode(stream):
    '''
        Method to decode streams using hexadecimal encoding
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    eod = '>'
    decodedStream = ''
    char = ''
    index = 0
    while index < len(stream):
        c = stream[index]
        if c == eod:
            if len(decodedStream) % 2 != 0:
                char += '0'
                try:
                    decodedStream += chr(int(char, base=16))
                except:
                    return (-1, 'Error in hexadecimal conversion')
            break
        elif c.isspace():
            index += 1
            continue
        char += c
        if len(char) == 2:
            try:
                decodedStream += chr(int(char, base=16))
            except:
                return (-1, 'Error in hexadecimal conversion')
            char = ''
        index += 1
    return (0, decodedStream)


def asciiHexEncode(stream):
    '''
        Method to encode streams using hexadecimal encoding
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    try:
        encodedStream = stream.encode('hex')
    except:
        return (-1, 'Error in hexadecimal conversion')
    return (0, encodedStream)


def flateDecode(stream, parameters):
    '''
        Method to decode streams using the Flate algorithm
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    try:
        decodedStream = zlib.decompress(stream)
    except:
        return (-1, 'Error decompressing string')

    if parameters == None or parameters == {}:
        return (0, decodedStream)
    else:
        if parameters.has_key('/Predictor'):
            predictor = parameters['/Predictor'].getRawValue()
        else:
            predictor = 1
        # Columns = number of samples per row
        if parameters.has_key('/Columns'):
            columns = parameters['/Columns'].getRawValue()
        else:
            columns = 1
        # Colors = number of components per sample
        if parameters.has_key('/Colors'):
            colors = parameters['/Colors'].getRawValue()
            if colors < 1:
                colors = 1
        else:
            colors = 1
        # BitsPerComponent: number of bits per color component
        if parameters.has_key('/BitsPerComponent'):
            bits = parameters['/BitsPerComponent'].getRawValue()
            if bits not in [1, 2, 4, 8, 16]:
                bits = 8
        else:
            bits = 8
        if predictor != None and predictor != 1:
            ret = post_prediction(decodedStream, predictor, columns, colors, bits)
            return ret
        else:
            return (0, decodedStream)


def flateEncode(stream, parameters):
    '''
        Method to encode streams using the Flate algorithm
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    if parameters == None or parameters == {}:
        try:
            return (0, zlib.compress(stream))
        except:
            return (-1, 'Error compressing string')
    else:
        if parameters.has_key('/Predictor'):
            predictor = parameters['/Predictor'].getRawValue()
        else:
            predictor = 1
        # Columns = number of samples per row
        if parameters.has_key('/Columns'):
            columns = parameters['/Columns'].getRawValue()
        else:
            columns = 1
        # Colors = number of components per sample
        if parameters.has_key('/Colors'):
            colors = parameters['/Colors'].getRawValue()
            if colors < 1:
                colors = 1
        else:
            colors = 1
        # BitsPerComponent: number of bits per color component
        if parameters.has_key('/BitsPerComponent'):
            bits = parameters['/BitsPerComponent'].getRawValue()
            if bits not in [1, 2, 4, 8, 16]:
                bits = 8
        else:
            bits = 8
        if predictor != None and predictor != 1:
            ret = pre_prediction(stream, predictor, columns, colors, bits)
            if ret[0] == -1:
                return ret
            output = ret[1]
        else:
            output = stream
        try:
            return (0, zlib.compress(output))
        except:
            return (-1, 'Error compressing string')


def lzwDecode(stream, parameters):
    '''
        Method to decode streams using the LZW algorithm
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    try:
        decodedStream = lzw.lzwdecode(stream)
    except:
        return (-1, 'Error decompressing string')

    if parameters == None or parameters == {}:
        return (0, decodedStream)
    else:
        if parameters.has_key('/Predictor'):
            predictor = parameters['/Predictor'].getRawValue()
        else:
            predictor = 1
        # Columns = number of samples per row
        if parameters.has_key('/Columns'):
            columns = parameters['/Columns'].getRawValue()
        else:
            columns = 1
        # Colors = number of components per sample
        if parameters.has_key('/Colors'):
            colors = parameters['/Colors'].getRawValue()
            if colors < 1:
                colors = 1
        else:
            colors = 1
        # BitsPerComponent: number of bits per color component
        if parameters.has_key('/BitsPerComponent'):
            bits = parameters['/BitsPerComponent'].getRawValue()
            if bits not in [1, 2, 4, 8, 16]:
                bits = 8
        else:
            bits = 8
        if parameters.has_key('/EarlyChange'):
            earlyChange = parameters['/EarlyChange'].getRawValue()
        else:
            earlyChange = 1
        if predictor != None and predictor != 1:
            ret = post_prediction(decodedStream, predictor, columns, colors, bits)
            return ret
        else:
            return (0, decodedStream)


def lzwEncode(stream, parameters):
    '''
        Method to encode streams using the LZW algorithm
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    if parameters == None or parameters == {}:
        try:
            generator = lzw.compress(stream)
            for c in generator:
                encodedStream += c
            return (0, encodedStream)
        except:
            return (-1, 'Error compressing string')
    else:
        if parameters.has_key('/Predictor'):
            predictor = parameters['/Predictor'].getRawValue()
        else:
            predictor = 1
        # Columns = number of samples per row
        if parameters.has_key('/Columns'):
            columns = parameters['/Columns'].getRawValue()
        else:
            columns = 1
        # Colors = number of components per sample
        if parameters.has_key('/Colors'):
            colors = parameters['/Colors'].getRawValue()
            if colors < 1:
                colors = 1
        else:
            colors = 1
        # BitsPerComponent: number of bits per color component
        if parameters.has_key('/BitsPerComponent'):
            bits = parameters['/BitsPerComponent'].getRawValue()
            if bits not in [1, 2, 4, 8, 16]:
                bits = 8
        else:
            bits = 8
        if parameters.has_key('/EarlyChange'):
            earlyChange = parameters['/EarlyChange'].getRawValue()
        else:
            earlyChange = 1
        if predictor != None and predictor != 1:
            ret = pre_prediction(stream, predictor, columns, colors, bits)
            if ret[0] == -1:
                return ret
            output = ret[1]
        else:
            output = stream
        try:
            generator = lzw.compress(output)
            for c in generator:
                encodedStream += c
            return (0, encodedStream)
        except:
            return (-1, 'Error decompressing string')


def pre_prediction(stream, predictor, columns, colors, bits):
    '''
        Predictor function to make the stream more predictable and improve compression (PDF Specification)
    
        @param stream: The stream to be modified
        @param predictor: The type of predictor to apply
        @param columns: Number of samples per row
        @param colors: Number of colors per sample
        @param bits: Number of bits per color
        @return: A tuple (status,statusContent), where statusContent is the modified stream in case status = 0 or an error in case status = -1
    '''

    output = ''
    #TODO: TIFF and more PNG predictions

    # PNG prediction
    if predictor >= 10 and predictor <= 15:
        # PNG prediction can vary from row to row
        for row in xrange(len(stream) / columns):
            rowdata = [ord(x) for x in stream[(row * columns):((row + 1) * columns)]]
            filterByte = predictor - 10
            rowdata = [filterByte] + rowdata
            if filterByte == 0:
                pass
            elif filterByte == 1:
                for i in range(len(rowdata) - 1, 1, -1):
                    if rowdata[i] < rowdata[i - 1]:
                        rowdata[i] = rowdata[i] + 256 - rowdata[i - 1]
                    else:
                        rowdata[i] = rowdata[i] - rowdata[i - 1]
            elif filterByte == 2:
                (-1, 'Unsupported predictor')
            else:
                return (-1, 'Unsupported predictor')
            output += (''.join([chr(x) for x in rowdata]))
        return (0, output)
    else:
        return (-1, 'Unsupported predictor')


def post_prediction(decodedStream, predictor, columns, colors, bits):
    '''
        Predictor function to obtain the real stream, removing the prediction (PDF Specification)
    
        @param decodedStream: The decoded stream to be modified
        @param predictor: The type of predictor to apply
        @param columns: Number of samples per row
        @param colors: Number of colors per sample
        @param bits: Number of bits per color
        @return: A tuple (status,statusContent), where statusContent is the modified decoded stream in case status = 0 or an error in case status = -1
    '''

    output = ''
    bytesPerRow = (colors * bits * columns + 7) / 8

    # TIFF - 2
    # http://www.gnupdf.org/PNG_and_TIFF_Predictors_Filter#TIFF
    if predictor == 2:
        numRows = len(decodedStream) / bytesPerRow
        bitmask = 2 ** bits - 1
        outputBitsStream = ''
        for rowIndex in range(numRows):
            row = decodedStream[rowIndex * bytesPerRow:rowIndex * bytesPerRow + bytesPerRow]
            ret, colorNums = getNumsFromBytes(row, bits)
            if ret == -1:
                return (ret, colorNums)
            pixel = [0 for x in range(colors)]
            for i in range(columns):
                for j in range(colors):
                    diffPixel = colorNums[i + j]
                    pixel[j] = (pixel[j] + diffPixel) & bitmask
                    ret, outputBits = getBitsFromNum(pixel[j], bits)
                    if ret == -1:
                        return (ret, outputBits)
                    outputBitsStream += outputBits
        output = getBytesFromBits(outputBitsStream)
        return output
    # PNG prediction
    # http://www.libpng.org/pub/png/spec/1.2/PNG-Filters.html
    # http://www.gnupdf.org/PNG_and_TIFF_Predictors_Filter#TIFF
    elif predictor >= 10 and predictor <= 15:
        bytesPerRow += 1
        numRows = (len(decodedStream) + bytesPerRow - 1) / bytesPerRow
        numSamplesPerRow = columns + 1
        bytesPerSample = (colors * bits + 7) / 8
        upRowdata = (0,) * numSamplesPerRow
        for row in xrange(numRows):
            rowdata = [ord(x) for x in decodedStream[(row * bytesPerRow):((row + 1) * bytesPerRow)]]
            # PNG prediction can vary from row to row
            filterByte = rowdata[0]
            rowdata[0] = 0

            if filterByte == 0:
                # None
                pass
            elif filterByte == 1:
                # Sub - 11
                for i in range(1, numSamplesPerRow):
                    if i < bytesPerSample:
                        prevSample = 0
                    else:
                        prevSample = rowdata[i - bytesPerSample]
                    rowdata[i] = (rowdata[i] + prevSample) % 256
            elif filterByte == 2:
                # Up - 12
                for i in range(1, numSamplesPerRow):
                    upSample = upRowdata[i]
                    rowdata[i] = (rowdata[i] + upSample) % 256
            elif filterByte == 3:
                # Average - 13
                for i in range(1, numSamplesPerRow):
                    upSample = upRowdata[i]
                    if i < bytesPerSample:
                        prevSample = 0
                    else:
                        prevSample = rowdata[i - bytesPerSample]
                    rowdata[i] = (rowdata[i] + ((prevSample + upSample) / 2)) % 256
            elif filterByte == 4:
                # Paeth - 14
                for i in range(1, numSamplesPerRow):
                    upSample = upRowdata[i]
                    if i < bytesPerSample:
                        prevSample = 0
                        upPrevSample = 0
                    else:
                        prevSample = rowdata[i - bytesPerSample]
                        upPrevSample = upRowdata[i - bytesPerSample]
                    p = prevSample + upSample - upPrevSample
                    pa = abs(p - prevSample)
                    pb = abs(p - upSample)
                    pc = abs(p - upPrevSample)
                    if pa <= pb and pa <= pc:
                        nearest = prevSample
                    elif pb <= pc:
                        nearest = upSample
                    else:
                        nearest = upPrevSample
                    rowdata[i] = (rowdata[i] + nearest) % 256
            else:
                # Optimum - 15
                #return (-1,'Unsupported predictor')
                pass
            upRowdata = rowdata
            output += (''.join([chr(x) for x in rowdata[1:]]))
        return (0, output)
    else:
        return (-1, 'Wrong value for predictor')


def runLengthDecode(stream):
    '''
        Method to decode streams using the Run-Length algorithm
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    index = 0
    try:
        while index < len(stream):
            length = ord(stream[index])
            if length >= 0 and length < 128:
                decodedStream += stream[index + 1:index + length + 2]
                index += length + 2
            elif length > 128 and length < 256:
                decodedStream += stream[index + 1] * (257 - length)
                index += 2
            else:
                break
    except:
        return (-1, 'Error decoding string')
    return (0, decodedStream)


def runLengthEncode(stream):
    '''
        Method to encode streams using the Run-Length algorithm (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    return (-1, 'RunLengthEncode not supported yet')


def ccittFaxDecode(stream, parameters):
    '''
        Method to decode streams using the CCITT facsimile standard
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''

    if parameters == None or parameters == {}:
        try:
            decodedStream = CCITTFax().decode(stream)
            return (0, decodedStream)
        except:
            return (-1, 'Error decompressing string')
    else:
        # K = A code identifying the encoding scheme used
        if parameters.has_key('/K'):
            k = parameters['/K'].getRawValue()
            if type(k) != int:
                k = 0
            else:
                if k != 0:
                    # Only supported "Group 3, 1-D" encoding (Pure one-dimensional encoding)
                    return (-1, 'CCITT encoding scheme not supported')
        else:
            k = 0
        # EndOfLine = A flag indicating whether end-of-line bit patterns are required to be present in the encoding.
        if parameters.has_key('/EndOfLine'):
            eol = parameters['/EndOfLine'].getRawValue()
            if eol == 'true':
                eol = True
            else:
                eol = False
        else:
            eol = False
        # EncodedByteAlign = A flag indicating whether the filter expects extra 0 bits before each encoded line so that the line begins on a byte boundary
        if parameters.has_key('/EncodedByteAlign'):
            byteAlign = parameters['/EncodedByteAlign'].getRawValue()
            if byteAlign == 'true':
                byteAlign = True
            else:
                byteAlign = False
        else:
            byteAlign = False
        # Columns = The width of the image in pixels.
        if parameters.has_key('/Columns'):
            columns = parameters['/Columns'].getRawValue()
            if type(columns) != int:
                columns = 1728
        else:
            columns = 1728
        # Rows = The height of the image in scan lines.
        if parameters.has_key('/Rows'):
            rows = parameters['/Rows'].getRawValue()
            if type(rows) != int:
                rows = 0
        else:
            rows = 0
        # EndOfBlock = number of samples per row
        if parameters.has_key('/EndOfBlock'):
            eob = parameters['/EndOfBlock'].getRawValue()
            if eob == 'false':
                eob = False
            else:
                eob = True
        else:
            eob = True
        # BlackIs1 = A flag indicating whether 1 bits are to be interpreted as black pixels and 0 bits as white pixels
        if parameters.has_key('/BlackIs1'):
            blackIs1 = parameters['/BlackIs1'].getRawValue()
            if blackIs1 == 'true':
                blackIs1 = True
            else:
                blackIs1 = False
        else:
            blackIs1 = False
        # DamagedRowsBeforeError = The number of damaged rows of data to be tolerated before an error occurs
        if parameters.has_key('/DamagedRowsBeforeError'):
            damagedRowsBeforeError = parameters['/DamagedRowsBeforeError'].getRawValue()
        else:
            damagedRowsBeforeError = 0
        try:
            decodedStream = CCITTFax().decode(stream, k, eol, byteAlign, columns, rows, eob, blackIs1,
                                              damagedRowsBeforeError)
            return (0, decodedStream)
        except:
            return (-1, 'Error decompressing string')


def ccittFaxEncode(stream, parameters):
    '''
        Method to encode streams using the CCITT facsimile standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    return (-1, 'CcittFaxEncode not supported yet')


def crypt(stream, parameters):
    '''
        Method to encrypt streams using a PDF security handler (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encrypted PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    if parameters == None or parameters == {}:
        return (0, stream)
    else:
        if not parameters.has_key('/Name') or parameters['/Name'] == None:
            return (0, stream)
        else:
            cryptFilterName = parameters['/Name'].getValue()
            if cryptFilterName == 'Identity':
                return (0, stream)
            else:
                #TODO: algorithm is cryptFilterName, specified in the /CF dictionary
                return (-1, 'Crypt not supported yet')


def decrypt(stream, parameters):
    '''
        Method to decrypt streams using a PDF security handler (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decrypted PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    if parameters == None or parameters == {}:
        return (0, stream)
    else:
        if not parameters.has_key('/Name') or parameters['/Name'] == None:
            return (0, stream)
        else:
            cryptFilterName = parameters['/Name'].getValue()
            if cryptFilterName == 'Identity':
                return (0, stream)
            else:
                #TODO: algorithm is cryptFilterName, specified in the /CF dictionary
                return (-1, 'Decrypt not supported yet')


def dctDecode(stream, parameters):
    '''
        Method to decode streams using a DCT technique based on the JPEG standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    try:
        from PIL import Image
        import StringIO
    except:
        return (-1, 'Python Imaging Library (PIL) not installed')
    # Quick implementation, assuming the library can detect the parameters
    try:
        im = Image.open(StringIO.StringIO(stream))
        decodedStream = im.tostring()
        return (0, decodedStream)
    except:
        return (-1, 'Error decompresing image data')


def dctEncode(stream, parameters):
    '''
        Method to encode streams using a DCT technique based on the JPEG standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    return (-1, 'DctEncode not supported yet')


def jbig2Decode(stream, parameters):
    '''
        Method to decode streams using the JBIG2 standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    return (-1, 'Jbig2Decode not supported yet')


def jbig2Encode(stream, parameters):
    '''
        Method to encode streams using the JBIG2 standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    return (-1, 'Jbig2Encode not supported yet')


def jpxDecode(stream):
    '''
        Method to decode streams using the JPEG2000 standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the decoded PDF stream in case status = 0 or an error in case status = -1
    '''
    decodedStream = ''
    return (-1, 'JpxDecode not supported yet')


def jpxEncode(stream):
    '''
        Method to encode streams using the JPEG2000 standard (NOT IMPLEMENTED YET)
    
        @param stream: A PDF stream
        @return: A tuple (status,statusContent), where statusContent is the encoded PDF stream in case status = 0 or an error in case status = -1
    '''
    encodedStream = ''
    return (-1, 'JpxEncode not supported yet')