# vim: sw=4:expandtab:foldmethod=marker
#
# 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
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# POSSIBILITY OF SUCH DAMAGE.
"""
Implementation of stream filters for PDF.
"""
__author__ = "Mathieu Fenniak"
__author_email__ = "biziqe@mathieu.fenniak.net"
import math
from .utils import PdfReadError, ord_, chr_, paethPredictor
from sys import version_info
if version_info < ( 3, 0 ):
from cStringIO import StringIO
else:
from io import StringIO
import struct
try:
import zlib
def decompress(data):
return zlib.decompress(data)
def compress(data):
return zlib.compress(data)
except ImportError:
# Unable to import zlib. Attempt to use the System.IO.Compression
# library from the .NET framework. (IronPython only)
import System
from System import IO, Collections, Array
def _string_to_bytearr(buf):
retval = Array.CreateInstance(System.Byte, len(buf))
for i in range(len(buf)):
retval[i] = ord(buf[i])
return retval
def _bytearr_to_string(bytes):
retval = ""
for i in range(bytes.Length):
retval += chr(bytes[i])
return retval
def _read_bytes(stream):
ms = IO.MemoryStream()
buf = Array.CreateInstance(System.Byte, 2048)
while True:
bytes = stream.Read(buf, 0, buf.Length)
if bytes == 0:
break
else:
ms.Write(buf, 0, bytes)
retval = ms.ToArray()
ms.Close()
return retval
def decompress(data):
bytes = _string_to_bytearr(data)
ms = IO.MemoryStream()
ms.Write(bytes, 0, bytes.Length)
ms.Position = 0 # fseek 0
gz = IO.Compression.DeflateStream(ms, IO.Compression.CompressionMode.Decompress)
bytes = _read_bytes(gz)
retval = _bytearr_to_string(bytes)
gz.Close()
return retval
def compress(data):
bytes = _string_to_bytearr(data)
ms = IO.MemoryStream()
gz = IO.Compression.DeflateStream(ms, IO.Compression.CompressionMode.Compress, True)
gz.Write(bytes, 0, bytes.Length)
gz.Close()
ms.Position = 0 # fseek 0
bytes = ms.ToArray()
retval = _bytearr_to_string(bytes)
ms.Close()
return retval
class FlateDecode(object):
def decode(data, decodeParms):
data = decompress(data)
predictor = 1
if decodeParms:
try:
predictor = decodeParms.get("/Predictor", 1)
except AttributeError:
pass # usually an array with a null object was read
# predictor 1 == no predictor
if predictor != 1:
columns = decodeParms["/Columns"]
# PNG prediction:
if predictor >= 10 and predictor <= 15:
output = StringIO()
# PNG prediction can vary from row to row
rowlength = columns + 1
assert len(data) % rowlength == 0
prev_rowdata = (0,) * rowlength
for row in range(len(data) // rowlength):
rowdata = [ord_(x) for x in data[(row*rowlength):((row+1)*rowlength)]]
filterByte = rowdata[0]
if filterByte == 0:
pass
elif filterByte == 1:
for i in range(2, rowlength):
rowdata[i] = (rowdata[i] + rowdata[i-1]) % 256
elif filterByte == 2:
for i in range(1, rowlength):
rowdata[i] = (rowdata[i] + prev_rowdata[i]) % 256
elif filterByte == 3:
for i in range(1, rowlength):
left = rowdata[i-1] if i > 1 else 0
floor = math.floor(left + prev_rowdata[i])/2
rowdata[i] = (rowdata[i] + int(floor)) % 256
elif filterByte == 4:
for i in range(1, rowlength):
left = rowdata[i - 1] if i > 1 else 0
up = prev_rowdata[i]
up_left = prev_rowdata[i - 1] if i > 1 else 0
paeth = paethPredictor(left, up, up_left)
rowdata[i] = (rowdata[i] + paeth) % 256
else:
# unsupported PNG filter
raise PdfReadError("Unsupported PNG filter %r" % filterByte)
prev_rowdata = rowdata
output.write(''.join([chr(x) for x in rowdata[1:]]))
data = output.getvalue()
else:
# unsupported predictor
raise PdfReadError("Unsupported flatedecode predictor %r" % predictor)
return data
decode = staticmethod(decode)
def encode(data):
return compress(data)
encode = staticmethod(encode)
class ASCIIHexDecode(object):
def decode(data, decodeParms=None):
retval = ""
char = ""
x = 0
while True:
c = data[x]
if c == ">":
break
elif c.isspace():
x += 1
continue
char += c
if len(char) == 2:
retval += chr(int(char, base=16))
char = ""
x += 1
assert char == ""
return retval
decode = staticmethod(decode)
class LZWDecode(object):
"""Taken from:
http://www.java2s.com/Open-Source/Java-Document/PDF/PDF-Renderer/com/sun/pdfview/decode/LZWDecode.java.htm
"""
class decoder(object):
def __init__(self, data):
self.STOP=257
self.CLEARDICT=256
self.data=data
self.bytepos=0
self.bitpos=0
self.dict=[""]*4096
for i in range(256):
self.dict[i]=chr(i)
self.resetDict()
def resetDict(self):
self.dictlen=258
self.bitspercode=9
def nextCode(self):
fillbits=self.bitspercode
value=0
while fillbits>0 :
if self.bytepos >= len(self.data):
return -1
nextbits=ord_(self.data[self.bytepos])
bitsfromhere=8-self.bitpos
if bitsfromhere>fillbits:
bitsfromhere=fillbits
value |= (((nextbits >> (8-self.bitpos-bitsfromhere)) &
(0xff >> (8-bitsfromhere))) <<
(fillbits-bitsfromhere))
fillbits -= bitsfromhere
self.bitpos += bitsfromhere
if self.bitpos >=8:
self.bitpos=0
self.bytepos = self.bytepos+1
return value
def decode(self):
""" algorithm derived from:
http://www.rasip.fer.hr/research/compress/algorithms/fund/lz/lzw.html
and the PDFReference
"""
cW = self.CLEARDICT;
baos=""
while True:
pW = cW;
cW = self.nextCode();
if cW == -1:
raise PdfReadError("Missed the stop code in LZWDecode!")
if cW == self.STOP:
break;
elif cW == self.CLEARDICT:
self.resetDict();
elif pW == self.CLEARDICT:
baos+=self.dict[cW]
else:
if cW < self.dictlen:
baos += self.dict[cW]
p=self.dict[pW]+self.dict[cW][0]
self.dict[self.dictlen]=p
self.dictlen+=1
else:
p=self.dict[pW]+self.dict[pW][0]
baos+=p
self.dict[self.dictlen] = p;
self.dictlen+=1
if (self.dictlen >= (1 << self.bitspercode) - 1 and
self.bitspercode < 12):
self.bitspercode+=1
return baos
@staticmethod
def decode(data,decodeParams=None):
return LZWDecode.decoder(data).decode()
class ASCII85Decode(object):
def decode(data, decodeParms=None):
if version_info < ( 3, 0 ):
retval = ""
group = []
x = 0
hitEod = False
# remove all whitespace from data
data = [y for y in data if not (y in ' \n\r\t')]
while not hitEod:
c = data[x]
if len(retval) == 0 and c == "<" and data[x+1] == "~":
x += 2
continue
#elif c.isspace():
# x += 1
# continue
elif c == 'z':
assert len(group) == 0
retval += '\x00\x00\x00\x00'
x += 1
continue
elif c == "~" and data[x+1] == ">":
if len(group) != 0:
# cannot have a final group of just 1 char
assert len(group) > 1
cnt = len(group) - 1
group += [ 85, 85, 85 ]
hitEod = cnt
else:
break
else:
c = ord(c) - 33
assert c >= 0 and c < 85
group += [ c ]
if len(group) >= 5:
b = group[0] * (85**4) + \
group[1] * (85**3) + \
group[2] * (85**2) + \
group[3] * 85 + \
group[4]
assert b < (2**32 - 1)
c4 = chr((b >> 0) % 256)
c3 = chr((b >> 8) % 256)
c2 = chr((b >> 16) % 256)
c1 = chr(b >> 24)
retval += (c1 + c2 + c3 + c4)
if hitEod:
retval = retval[:-4+hitEod]
group = []
x += 1
return retval
else:
if isinstance(data, str):
data = data.encode('ascii')
n = b = 0
out = bytearray()
for c in data:
if ord('!') <= c and c <= ord('u'):
n += 1
b = b*85+(c-33)
if n == 5:
out += struct.pack(b'>L',b)
n = b = 0
elif c == ord('z'):
assert n == 0
out += b'\0\0\0\0'
elif c == ord('~'):
if n:
for _ in range(5-n):
b = b*85+84
out += struct.pack(b'>L',b)[:n-1]
break
return bytes(out)
decode = staticmethod(decode)
class DCTDecode(object):
def decode(data, decodeParms=None):
return data
decode = staticmethod(decode)
class JPXDecode(object):
def decode(data, decodeParms=None):
return data
decode = staticmethod(decode)
class CCITTFaxDecode(object):
def decode(data, decodeParms=None, height=0):
if decodeParms:
if decodeParms.get("/K", 1) == -1:
CCITTgroup = 4
else:
CCITTgroup = 3
width = decodeParms["/Columns"]
imgSize = len(data)
tiff_header_struct = '<' + '2s' + 'h' + 'l' + 'h' + 'hhll' * 8 + 'h'
tiffHeader = struct.pack(tiff_header_struct,
b'II', # Byte order indication: Little endian
42, # Version number (always 42)
8, # Offset to first IFD
8, # Number of tags in IFD
256, 4, 1, width, # ImageWidth, LONG, 1, width
257, 4, 1, height, # ImageLength, LONG, 1, length
258, 3, 1, 1, # BitsPerSample, SHORT, 1, 1
259, 3, 1, CCITTgroup, # Compression, SHORT, 1, 4 = CCITT Group 4 fax encoding
262, 3, 1, 0, # Thresholding, SHORT, 1, 0 = WhiteIsZero
273, 4, 1, struct.calcsize(tiff_header_struct), # StripOffsets, LONG, 1, length of header
278, 4, 1, height, # RowsPerStrip, LONG, 1, length
279, 4, 1, imgSize, # StripByteCounts, LONG, 1, size of image
0 # last IFD
)
return tiffHeader + data
decode = staticmethod(decode)
def decodeStreamData(stream):
from .generic import NameObject
filters = stream.get("/Filter", ())
if len(filters) and not isinstance(filters[0], NameObject):
# we have a single filter instance
filters = (filters,)
data = stream._data
# If there is not data to decode we should not try to decode the data.
if data:
for filterType in filters:
if filterType == "/FlateDecode" or filterType == "/Fl":
data = FlateDecode.decode(data, stream.get("/DecodeParms"))
elif filterType == "/ASCIIHexDecode" or filterType == "/AHx":
data = ASCIIHexDecode.decode(data)
elif filterType == "/LZWDecode" or filterType == "/LZW":
data = LZWDecode.decode(data, stream.get("/DecodeParms"))
elif filterType == "/ASCII85Decode" or filterType == "/A85":
data = ASCII85Decode.decode(data)
elif filterType == "/DCTDecode":
data = DCTDecode.decode(data)
elif filterType == "/JPXDecode":
data = JPXDecode.decode(data)
elif filterType == "/CCITTFaxDecode":
height = stream.get("/Height", ())
data = CCITTFaxDecode.decode(data, stream.get("/DecodeParms"), height)
elif filterType == "/Crypt":
decodeParams = stream.get("/DecodeParams", {})
if "/Name" not in decodeParams and "/Type" not in decodeParams:
pass
else:
raise NotImplementedError("/Crypt filter with /Name or /Type not supported yet")
else:
# unsupported filter
raise NotImplementedError("unsupported filter %s" % filterType)
return data