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pdf.py
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# -*- coding: utf-8 -*-
#
# This file is part of Invenio.
# Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 CERN.
#
# Invenio 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 2 of the
# License, or (at your option) any later version.
#
# Invenio 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 Invenio; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
"""
When a document is converted to plain-text from PDF,
certain characters may result in the plain-text, that are
either unwanted, or broken. These characters need to be corrected
or removed. Examples are, certain control characters that would
be illegal in XML and must be removed; TeX ligatures (etc); broken
accents such as umlauts on letters that must be corrected.
This function returns a dictionary of (unwanted) characters to look
for and the characters that should be used to replace them.
@return: (dictionary) - { seek -> replace, } or charsacters to
replace in plain-text.
"""
import re
import subprocess
from six import iteritems
from invenio.config import CFG_PATH_PDFTOTEXT
from invenio.legacy.docextract.utils import write_message
# a dictionary of undesirable characters and their replacements:
UNDESIRABLE_CHAR_REPLACEMENTS = {
# Control characters not allowed in XML:
u'\u2028' : u"",
u'\u2029' : u"",
u'\u202A' : u"",
u'\u202B' : u"",
u'\u202C' : u"",
u'\u202D' : u"",
u'\u202E' : u"",
u'\u206A' : u"",
u'\u206B' : u"",
u'\u206C' : u"",
u'\u206D' : u"",
u'\u206E' : u"",
u'\u206F' : u"",
u'\uFFF9' : u"",
u'\uFFFA' : u"",
u'\uFFFB' : u"",
u'\uFFFC' : u"",
u'\uFEFF' : u"",
# Remove the result of a bad UTF-8 character
u'\uFFFF' : u"",
# Language Tag Code Points:
u"\U000E0000" : u"",
u"\U000E0001" : u"",
u"\U000E0002" : u"",
u"\U000E0003" : u"",
u"\U000E0004" : u"",
u"\U000E0005" : u"",
u"\U000E0006" : u"",
u"\U000E0007" : u"",
u"\U000E0008" : u"",
u"\U000E0009" : u"",
u"\U000E000A" : u"",
u"\U000E000B" : u"",
u"\U000E000C" : u"",
u"\U000E000D" : u"",
u"\U000E000E" : u"",
u"\U000E000F" : u"",
u"\U000E0010" : u"",
u"\U000E0011" : u"",
u"\U000E0012" : u"",
u"\U000E0013" : u"",
u"\U000E0014" : u"",
u"\U000E0015" : u"",
u"\U000E0016" : u"",
u"\U000E0017" : u"",
u"\U000E0018" : u"",
u"\U000E0019" : u"",
u"\U000E001A" : u"",
u"\U000E001B" : u"",
u"\U000E001C" : u"",
u"\U000E001D" : u"",
u"\U000E001E" : u"",
u"\U000E001F" : u"",
u"\U000E0020" : u"",
u"\U000E0021" : u"",
u"\U000E0022" : u"",
u"\U000E0023" : u"",
u"\U000E0024" : u"",
u"\U000E0025" : u"",
u"\U000E0026" : u"",
u"\U000E0027" : u"",
u"\U000E0028" : u"",
u"\U000E0029" : u"",
u"\U000E002A" : u"",
u"\U000E002B" : u"",
u"\U000E002C" : u"",
u"\U000E002D" : u"",
u"\U000E002E" : u"",
u"\U000E002F" : u"",
u"\U000E0030" : u"",
u"\U000E0031" : u"",
u"\U000E0032" : u"",
u"\U000E0033" : u"",
u"\U000E0034" : u"",
u"\U000E0035" : u"",
u"\U000E0036" : u"",
u"\U000E0037" : u"",
u"\U000E0038" : u"",
u"\U000E0039" : u"",
u"\U000E003A" : u"",
u"\U000E003B" : u"",
u"\U000E003C" : u"",
u"\U000E003D" : u"",
u"\U000E003E" : u"",
u"\U000E003F" : u"",
u"\U000E0040" : u"",
u"\U000E0041" : u"",
u"\U000E0042" : u"",
u"\U000E0043" : u"",
u"\U000E0044" : u"",
u"\U000E0045" : u"",
u"\U000E0046" : u"",
u"\U000E0047" : u"",
u"\U000E0048" : u"",
u"\U000E0049" : u"",
u"\U000E004A" : u"",
u"\U000E004B" : u"",
u"\U000E004C" : u"",
u"\U000E004D" : u"",
u"\U000E004E" : u"",
u"\U000E004F" : u"",
u"\U000E0050" : u"",
u"\U000E0051" : u"",
u"\U000E0052" : u"",
u"\U000E0053" : u"",
u"\U000E0054" : u"",
u"\U000E0055" : u"",
u"\U000E0056" : u"",
u"\U000E0057" : u"",
u"\U000E0058" : u"",
u"\U000E0059" : u"",
u"\U000E005A" : u"",
u"\U000E005B" : u"",
u"\U000E005C" : u"",
u"\U000E005D" : u"",
u"\U000E005E" : u"",
u"\U000E005F" : u"",
u"\U000E0060" : u"",
u"\U000E0061" : u"",
u"\U000E0062" : u"",
u"\U000E0063" : u"",
u"\U000E0064" : u"",
u"\U000E0065" : u"",
u"\U000E0066" : u"",
u"\U000E0067" : u"",
u"\U000E0068" : u"",
u"\U000E0069" : u"",
u"\U000E006A" : u"",
u"\U000E006B" : u"",
u"\U000E006C" : u"",
u"\U000E006D" : u"",
u"\U000E006E" : u"",
u"\U000E006F" : u"",
u"\U000E0070" : u"",
u"\U000E0071" : u"",
u"\U000E0072" : u"",
u"\U000E0073" : u"",
u"\U000E0074" : u"",
u"\U000E0075" : u"",
u"\U000E0076" : u"",
u"\U000E0077" : u"",
u"\U000E0078" : u"",
u"\U000E0079" : u"",
u"\U000E007A" : u"",
u"\U000E007B" : u"",
u"\U000E007C" : u"",
u"\U000E007D" : u"",
u"\U000E007E" : u"",
u"\U000E007F" : u"",
# Musical Notation Scoping
u"\U0001D173" : u"",
u"\U0001D174" : u"",
u"\U0001D175" : u"",
u"\U0001D176" : u"",
u"\U0001D177" : u"",
u"\U0001D178" : u"",
u"\U0001D179" : u"",
u"\U0001D17A" : u"",
u'\u0000' : u"", # NULL
u'\u0001' : u"", # START OF HEADING
# START OF TEXT & END OF TEXT:
u'\u0002' : u"",
u'\u0003' : u"",
u'\u0004' : u"", # END OF TRANSMISSION
# ENQ and ACK
u'\u0005' : u"",
u'\u0006' : u"",
u'\u0007' : u"", # BELL
u'\u0008' : u"", # BACKSPACE
# SHIFT-IN & SHIFT-OUT
u'\u000E' : u"",
u'\u000F' : u"",
# Other controls:
u'\u0010' : u"", # DATA LINK ESCAPE
u'\u0011' : u"", # DEVICE CONTROL ONE
u'\u0012' : u"", # DEVICE CONTROL TWO
u'\u0013' : u"", # DEVICE CONTROL THREE
u'\u0014' : u"", # DEVICE CONTROL FOUR
u'\u0015' : u"", # NEGATIVE ACK
u'\u0016' : u"", # SYNCRONOUS IDLE
u'\u0017' : u"", # END OF TRANSMISSION BLOCK
u'\u0018' : u"", # CANCEL
u'\u0019' : u"", # END OF MEDIUM
u'\u001A' : u"", # SUBSTITUTE
u'\u001B' : u"", # ESCAPE
u'\u001C' : u"", # INFORMATION SEPARATOR FOUR (file separator)
u'\u001D' : u"", # INFORMATION SEPARATOR THREE (group separator)
u'\u001E' : u"", # INFORMATION SEPARATOR TWO (record separator)
u'\u001F' : u"", # INFORMATION SEPARATOR ONE (unit separator)
# \r -> remove it
u'\r' : u"",
# Strange parantheses - change for normal:
u'\x1c' : u'(',
u'\x1d' : u')',
# Some ff from tex:
u'\u0013\u0010' : u'\u00ED',
u'\x0b' : u'ff',
# fi from tex:
u'\x0c' : u'fi',
# ligatures from TeX:
u'\ufb00' : u'ff',
u'\ufb01' : u'fi',
u'\ufb02' : u'fl',
u'\ufb03' : u'ffi',
u'\ufb04' : u'ffl',
# Superscripts from TeX
u'\u2212' : u'-',
u'\u2013' : u'-',
# Word style speech marks:
u'\u201c ': u'"',
u'\u201d' : u'"',
u'\u201c' : u'"',
# pdftotext has problems with umlaut and prints it as diaeresis
# followed by a letter:correct it
# (Optional space between char and letter - fixes broken
# line examples)
u'\u00A8 a' : u'\u00E4',
u'\u00A8 e' : u'\u00EB',
u'\u00A8 i' : u'\u00EF',
u'\u00A8 o' : u'\u00F6',
u'\u00A8 u' : u'\u00FC',
u'\u00A8 y' : u'\u00FF',
u'\u00A8 A' : u'\u00C4',
u'\u00A8 E' : u'\u00CB',
u'\u00A8 I' : u'\u00CF',
u'\u00A8 O' : u'\u00D6',
u'\u00A8 U' : u'\u00DC',
u'\u00A8 Y' : u'\u0178',
u'\xA8a' : u'\u00E4',
u'\xA8e' : u'\u00EB',
u'\xA8i' : u'\u00EF',
u'\xA8o' : u'\u00F6',
u'\xA8u' : u'\u00FC',
u'\xA8y' : u'\u00FF',
u'\xA8A' : u'\u00C4',
u'\xA8E' : u'\u00CB',
u'\xA8I' : u'\u00CF',
u'\xA8O' : u'\u00D6',
u'\xA8U' : u'\u00DC',
u'\xA8Y' : u'\u0178',
# More umlaut mess to correct:
u'\x7fa' : u'\u00E4',
u'\x7fe' : u'\u00EB',
u'\x7fi' : u'\u00EF',
u'\x7fo' : u'\u00F6',
u'\x7fu' : u'\u00FC',
u'\x7fy' : u'\u00FF',
u'\x7fA' : u'\u00C4',
u'\x7fE' : u'\u00CB',
u'\x7fI' : u'\u00CF',
u'\x7fO' : u'\u00D6',
u'\x7fU' : u'\u00DC',
u'\x7fY' : u'\u0178',
u'\x7f a' : u'\u00E4',
u'\x7f e' : u'\u00EB',
u'\x7f i' : u'\u00EF',
u'\x7f o' : u'\u00F6',
u'\x7f u' : u'\u00FC',
u'\x7f y' : u'\u00FF',
u'\x7f A' : u'\u00C4',
u'\x7f E' : u'\u00CB',
u'\x7f I' : u'\u00CF',
u'\x7f O' : u'\u00D6',
u'\x7f U' : u'\u00DC',
u'\x7f Y' : u'\u0178',
# pdftotext: fix accute accent:
u'\x13a' : u'\u00E1',
u'\x13e' : u'\u00E9',
u'\x13i' : u'\u00ED',
u'\x13o' : u'\u00F3',
u'\x13u' : u'\u00FA',
u'\x13y' : u'\u00FD',
u'\x13A' : u'\u00C1',
u'\x13E' : u'\u00C9',
u'\x13I' : u'\u00CD',
u'\x13ı' : u'\u00ED', # Lower case turkish 'i' (dotless i)
u'\x13O' : u'\u00D3',
u'\x13U' : u'\u00DA',
u'\x13Y' : u'\u00DD',
u'\x13 a' : u'\u00E1',
u'\x13 e' : u'\u00E9',
u'\x13 i' : u'\u00ED',
u'\x13 o' : u'\u00F3',
u'\x13 u' : u'\u00FA',
u'\x13 y' : u'\u00FD',
u'\x13 A' : u'\u00C1',
u'\x13 E' : u'\u00C9',
u'\x13 I' : u'\u00CD',
u'\x13 ı' : u'\u00ED',
u'\x13 O' : u'\u00D3',
u'\x13 U' : u'\u00DA',
u'\x13 Y' : u'\u00DD',
u'\u00B4 a' : u'\u00E1',
u'\u00B4 e' : u'\u00E9',
u'\u00B4 i' : u'\u00ED',
u'\u00B4 o' : u'\u00F3',
u'\u00B4 u' : u'\u00FA',
u'\u00B4 y' : u'\u00FD',
u'\u00B4 A' : u'\u00C1',
u'\u00B4 E' : u'\u00C9',
u'\u00B4 I' : u'\u00CD',
u'\u00B4 ı' : u'\u00ED',
u'\u00B4 O' : u'\u00D3',
u'\u00B4 U' : u'\u00DA',
u'\u00B4 Y' : u'\u00DD',
u'\u00B4a' : u'\u00E1',
u'\u00B4e' : u'\u00E9',
u'\u00B4i' : u'\u00ED',
u'\u00B4o' : u'\u00F3',
u'\u00B4u' : u'\u00FA',
u'\u00B4y' : u'\u00FD',
u'\u00B4A' : u'\u00C1',
u'\u00B4E' : u'\u00C9',
u'\u00B4I' : u'\u00CD',
u'\u00B4ı' : u'\u00ED',
u'\u00B4O' : u'\u00D3',
u'\u00B4U' : u'\u00DA',
u'\u00B4Y' : u'\u00DD',
# pdftotext: fix grave accent:
u'\u0060 a' : u'\u00E0',
u'\u0060 e' : u'\u00E8',
u'\u0060 i' : u'\u00EC',
u'\u0060 o' : u'\u00F2',
u'\u0060 u' : u'\u00F9',
u'\u0060 A' : u'\u00C0',
u'\u0060 E' : u'\u00C8',
u'\u0060 I' : u'\u00CC',
u'\u0060 O' : u'\u00D2',
u'\u0060 U' : u'\u00D9',
u'\u0060a' : u'\u00E0',
u'\u0060e' : u'\u00E8',
u'\u0060i' : u'\u00EC',
u'\u0060o' : u'\u00F2',
u'\u0060u' : u'\u00F9',
u'\u0060A' : u'\u00C0',
u'\u0060E' : u'\u00C8',
u'\u0060I' : u'\u00CC',
u'\u0060O' : u'\u00D2',
u'\u0060U' : u'\u00D9',
u'a´': u'á',
u'i´': u'í',
u'e´': u'é',
u'u´': u'ú',
u'o´': u'ó',
# \02C7 : caron
u'\u02C7C' : u'\u010C',
u'\u02C7c' : u'\u010D',
u'\u02C7S' : u'\u0160',
u'\u02C7s' : u'\u0161',
u'\u02C7Z' : u'\u017D',
u'\u02C7z' : u'\u017E',
# \027 : aa (a with ring above)
u'\u02DAa' : u'\u00E5',
u'\u02DAA' : u'\u00C5',
# \030 : cedilla
u'\u0327c' : u'\u00E7',
u'\u0327C' : u'\u00C7',
u'¸c': u'ç',
# \02DC : tilde
u'\u02DCn' : u'\u00F1',
u'\u02DCN' : u'\u00D1',
u'\u02DCo' : u'\u00F5',
u'\u02DCO' : u'\u00D5',
u'\u02DCa' : u'\u00E3',
u'\u02DCA' : u'\u00C3',
u'\u02DCs' : u'\u0303s', # Combining tilde with 's'
# Circumflex accent (caret accent)
u'aˆ': u'â',
u'iˆ': u'î',
u'eˆ': u'ê',
u'uˆ': u'û',
u'oˆ': u'ô',
u'ˆa': u'â',
u'ˆi': u'î',
u'ˆe': u'ê',
u'ˆu': u'û',
u'ˆo': u'ô',
}
UNDESIRABLE_STRING_REPLACEMENTS = [
(u'\u201c ', '"'),
]
def replace_undesirable_characters(line):
"""
Replace certain bad characters in a text line.
@param line: (string) the text line in which bad characters are to
be replaced.
@return: (string) the text line after the bad characters have been
replaced.
"""
# These are separate because we want a particular order
for bad_string, replacement in UNDESIRABLE_STRING_REPLACEMENTS:
line = line.replace(bad_string, replacement)
for bad_char, replacement in iteritems(UNDESIRABLE_CHAR_REPLACEMENTS):
line = line.replace(bad_char, replacement)
return line
def pdftotext_conversion_is_bad(txtlines):
"""Sometimes pdftotext performs a bad conversion which consists of many
spaces and garbage characters.
This method takes a list of strings obtained from a pdftotext conversion
and examines them to see if they are likely to be the result of a bad
conversion.
@param txtlines: (list) of unicode strings obtained from pdftotext
conversion.
@return: (integer) - 1 if bad conversion; 0 if good conversion.
"""
# Numbers of 'words' and 'whitespaces' found in document:
numWords = numSpaces = 0
# whitespace character pattern:
p_space = re.compile(unicode(r'(\s)'), re.UNICODE)
# non-whitespace 'word' pattern:
p_noSpace = re.compile(unicode(r'(\S+)'), re.UNICODE)
for txtline in txtlines:
numWords = numWords + len(p_noSpace.findall(txtline.strip()))
numSpaces = numSpaces + len(p_space.findall(txtline.strip()))
if numSpaces >= (numWords * 3):
# Too many spaces - probably bad conversion
return True
else:
return False
def convert_PDF_to_plaintext(fpath, keep_layout=False):
""" Convert PDF to txt using pdftotext
Take the path to a PDF file and run pdftotext for this file, capturing
the output.
@param fpath: (string) path to the PDF file
@return: (list) of unicode strings (contents of the PDF file translated
into plaintext; each string is a line in the document.)
"""
if keep_layout:
layout_option = "-layout"
else:
layout_option = "-raw"
status = 0
doclines = []
# Pattern to check for lines with a leading page-break character.
# If this pattern is matched, we want to split the page-break into
# its own line because we rely upon this for trying to strip headers
# and footers, and for some other pattern matching.
p_break_in_line = re.compile(ur'^\s*\f(.+)$', re.UNICODE)
# build pdftotext command:
cmd_pdftotext = [CFG_PATH_PDFTOTEXT, layout_option, "-q",
"-enc", "UTF-8", fpath, "-"]
write_message("* %s" % ' '.join(cmd_pdftotext), verbose=2)
# open pipe to pdftotext:
pipe_pdftotext = subprocess.Popen(cmd_pdftotext, stdout=subprocess.PIPE)
# read back results:
for docline in pipe_pdftotext.stdout:
unicodeline = docline.decode("utf-8")
# Check for a page-break in this line:
m_break_in_line = p_break_in_line.match(unicodeline)
if m_break_in_line is None:
# There was no page-break in this line. Just add the line:
doclines.append(unicodeline)
else:
# If there was a page-break character in the same line as some
# text, split it out into its own line so that we can later
# try to find headers and footers:
doclines.append(u"\f")
doclines.append(m_break_in_line.group(1))
write_message("* convert_PDF_to_plaintext found: " \
"%s lines of text" % len(doclines), verbose=2)
# finally, check conversion result not bad:
if pdftotext_conversion_is_bad(doclines):
status = 2
doclines = []
return (doclines, status)

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