287 lines
8.0 KiB
Python
287 lines
8.0 KiB
Python
#!/usr/bin/env python
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import zlib
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from lzw import lzwdecode
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from ascii85 import ascii85decode, asciihexdecode
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from runlength import rldecode
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from ccitt import ccittfaxdecode
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from psparser import PSException, PSObject
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from psparser import LIT, STRICT
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from utils import apply_png_predictor, isnumber
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LITERAL_CRYPT = LIT('Crypt')
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# Abbreviation of Filter names in PDF 4.8.6. "Inline Images"
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LITERALS_FLATE_DECODE = (LIT('FlateDecode'), LIT('Fl'))
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LITERALS_LZW_DECODE = (LIT('LZWDecode'), LIT('LZW'))
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LITERALS_ASCII85_DECODE = (LIT('ASCII85Decode'), LIT('A85'))
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LITERALS_ASCIIHEX_DECODE = (LIT('ASCIIHexDecode'), LIT('AHx'))
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LITERALS_RUNLENGTH_DECODE = (LIT('RunLengthDecode'), LIT('RL'))
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LITERALS_CCITTFAX_DECODE = (LIT('CCITTFaxDecode'), LIT('CCF'))
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LITERALS_DCT_DECODE = (LIT('DCTDecode'), LIT('DCT'))
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## PDF Objects
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##
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class PDFObject(PSObject):
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pass
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class PDFException(PSException):
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pass
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class PDFTypeError(PDFException):
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pass
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class PDFValueError(PDFException):
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pass
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class PDFObjectNotFound(PDFException):
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pass
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class PDFNotImplementedError(PDFException):
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pass
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## PDFObjRef
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##
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class PDFObjRef(PDFObject):
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def __init__(self, doc, objid, _):
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if objid == 0:
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if STRICT:
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raise PDFValueError('PDF object id cannot be 0.')
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self.doc = doc
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self.objid = objid
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#self.genno = genno # Never used.
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return
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def __repr__(self):
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return '<PDFObjRef:%d>' % (self.objid)
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def resolve(self, default=None):
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try:
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return self.doc.getobj(self.objid)
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except PDFObjectNotFound:
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return default
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# resolve
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def resolve1(x, default=None):
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"""Resolves an object.
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If this is an array or dictionary, it may still contains
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some indirect objects inside.
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"""
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while isinstance(x, PDFObjRef):
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x = x.resolve(default=default)
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return x
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def resolve_all(x, default=None):
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"""Recursively resolves the given object and all the internals.
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Make sure there is no indirect reference within the nested object.
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This procedure might be slow.
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"""
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while isinstance(x, PDFObjRef):
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x = x.resolve(default=default)
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if isinstance(x, list):
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x = [resolve_all(v, default=default) for v in x]
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elif isinstance(x, dict):
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for (k, v) in x.iteritems():
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x[k] = resolve_all(v, default=default)
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return x
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def decipher_all(decipher, objid, genno, x):
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"""Recursively deciphers the given object.
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"""
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if isinstance(x, str):
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return decipher(objid, genno, x)
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if isinstance(x, list):
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x = [decipher_all(decipher, objid, genno, v) for v in x]
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elif isinstance(x, dict):
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for (k, v) in x.iteritems():
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x[k] = decipher_all(decipher, objid, genno, v)
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return x
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# Type cheking
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def int_value(x):
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x = resolve1(x)
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if not isinstance(x, int):
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if STRICT:
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raise PDFTypeError('Integer required: %r' % x)
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return 0
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return x
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def float_value(x):
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x = resolve1(x)
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if not isinstance(x, float):
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if STRICT:
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raise PDFTypeError('Float required: %r' % x)
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return 0.0
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return x
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def num_value(x):
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x = resolve1(x)
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if not isnumber(x):
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if STRICT:
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raise PDFTypeError('Int or Float required: %r' % x)
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return 0
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return x
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def str_value(x):
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x = resolve1(x)
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if not isinstance(x, str):
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if STRICT:
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raise PDFTypeError('String required: %r' % x)
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return ''
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return x
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def list_value(x):
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x = resolve1(x)
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if not isinstance(x, (list, tuple)):
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if STRICT:
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raise PDFTypeError('List required: %r' % x)
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return []
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return x
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def dict_value(x):
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x = resolve1(x)
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if not isinstance(x, dict):
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if STRICT:
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raise PDFTypeError('Dict required: %r' % x)
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return {}
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return x
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def stream_value(x):
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x = resolve1(x)
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if not isinstance(x, PDFStream):
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if STRICT:
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raise PDFTypeError('PDFStream required: %r' % x)
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return PDFStream({}, '')
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return x
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## PDFStream type
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##
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class PDFStream(PDFObject):
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def __init__(self, attrs, rawdata, decipher=None):
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assert isinstance(attrs, dict)
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self.attrs = attrs
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self.rawdata = rawdata
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self.decipher = decipher
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self.data = None
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self.objid = None
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self.genno = None
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return
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def set_objid(self, objid, genno):
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self.objid = objid
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self.genno = genno
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return
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def __repr__(self):
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if self.data is None:
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assert self.rawdata is not None
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return '<PDFStream(%r): raw=%d, %r>' % (self.objid, len(self.rawdata), self.attrs)
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else:
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assert self.data is not None
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return '<PDFStream(%r): len=%d, %r>' % (self.objid, len(self.data), self.attrs)
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def __contains__(self, name):
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return name in self.attrs
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def __getitem__(self, name):
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return self.attrs[name]
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def get(self, name, default=None):
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return self.attrs.get(name, default)
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def get_any(self, names, default=None):
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for name in names:
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if name in self.attrs:
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return self.attrs[name]
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return default
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def get_filters(self):
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filters = self.get_any(('F', 'Filter'))
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if not filters:
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return []
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if isinstance(filters, list):
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return filters
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return [filters]
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def decode(self):
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assert self.data is None and self.rawdata is not None
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data = self.rawdata
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if self.decipher:
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# Handle encryption
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data = self.decipher(self.objid, self.genno, data)
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filters = self.get_filters()
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if not filters:
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self.data = data
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self.rawdata = None
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return
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for f in filters:
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params = self.get_any(('DP', 'DecodeParms', 'FDecodeParms'), {})
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if f in LITERALS_FLATE_DECODE:
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# will get errors if the document is encrypted.
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try:
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data = zlib.decompress(data)
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except zlib.error, e:
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if STRICT:
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raise PDFException('Invalid zlib bytes: %r, %r' % (e, data))
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data = ''
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elif f in LITERALS_LZW_DECODE:
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data = lzwdecode(data)
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elif f in LITERALS_ASCII85_DECODE:
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data = ascii85decode(data)
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elif f in LITERALS_ASCIIHEX_DECODE:
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data = asciihexdecode(data)
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elif f in LITERALS_RUNLENGTH_DECODE:
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data = rldecode(data)
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elif f in LITERALS_CCITTFAX_DECODE:
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data = ccittfaxdecode(data, params)
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elif f in LITERALS_DCT_DECODE:
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# This is probably a JPG stream - it does not need to be decoded twice.
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# Just return the stream to the user.
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pass
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elif f == LITERAL_CRYPT:
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# not yet..
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raise PDFNotImplementedError('/Crypt filter is unsupported')
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else:
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raise PDFNotImplementedError('Unsupported filter: %r' % f)
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# apply predictors
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if 'Predictor' in params:
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pred = int_value(params['Predictor'])
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if pred == 1:
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# no predictor
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pass
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elif 10 <= pred:
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# PNG predictor
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colors = int_value(params.get('Colors', 1))
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columns = int_value(params.get('Columns', 1))
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bitspercomponent = int_value(params.get('BitsPerComponent', 8))
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data = apply_png_predictor(pred, colors, columns, bitspercomponent, data)
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else:
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raise PDFNotImplementedError('Unsupported predictor: %r' % pred)
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self.data = data
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self.rawdata = None
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return
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def get_data(self):
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if self.data is None:
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self.decode()
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return self.data
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def get_rawdata(self):
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return self.rawdata
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