Source code for tools.djvu

"""Wrapper around djvulibre to access djvu files properties and content."""
#
# (C) Pywikibot team, 2015-2023
#
# Distributed under the terms of the MIT license.
#
from __future__ import annotations

import os
import re
import subprocess
from collections import Counter

import pywikibot


def _call_cmd(args, lib: str = 'djvulibre') -> tuple:
    """
    Tiny wrapper around subprocess.Popen().

    :param args: same as Popen()
    :type args: str or typing.Sequence[string]
    :param lib: library to be logged in logging messages
    :return: returns a tuple (res, stdoutdata), where
        res is True if dp.returncode != 0 else False
    """
    if not isinstance(args, str):
        # upcast any param in sequence args to str
        cmd = ' '.join(str(a) for a in args)
    else:
        cmd = args

    dp = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    stdoutdata, stderrdata = dp.communicate()

    if dp.returncode != 0:
        pywikibot.error(f'{lib} error; {cmd}')
        pywikibot.error(str(stderrdata))
        return (False, stdoutdata)

    pywikibot.log(f'SUCCESS: {cmd} (PID: {dp.pid})')

    return (True, stdoutdata)


[docs] class DjVuFile: """Wrapper around djvulibre to access djvu files properties and content. Perform file existence checks. Control characters in djvu text-layer are converted for convenience (see http://djvu.sourceforge.net/doc/man/djvused.html for control chars details). """ def __init__(self, file: str) -> None: """ Initializer. :param file: filename (including path) to djvu file """ self._filename = file filename = os.path.expanduser(file) filename = os.path.abspath(filename) # Check file exists and has read permissions. with open(filename): self.file = filename self.dirname = os.path.dirname(filename) # pattern for parsing of djvudump output. self._pat_form = re.compile( r' *?FORM:DJVU *?\[\d+\] *?(?P<id>{[^\}]*?})? *?\[P(?P<n>\d+)\]') self._pat_info = re.compile( r'DjVu.*?(?P<size>\d+x\d+).*?(?P<dpi>\d+) dpi') def __repr__(self) -> str: """Return a more complete string representation.""" return f"{self.__module__}.{type(self).__name__}('{self._filename}')" def __str__(self) -> str: """Return a string representation.""" return f"{self.__class__.__name__}('{self._filename}')"
[docs] def check_cache(fn): """Decorator to check if cache shall be cleared.""" cache = ['_page_count', '_has_text', '_page_info'] def wrapper(obj, *args, **kwargs): force = kwargs.get('force', False) if force: for el in cache: obj.__dict__.pop(el, None) return fn(obj, *args, **kwargs) return wrapper
[docs] def check_page_number(fn): """Decorator to check if page number is valid. :raises ValueError """ def wrapper(obj, *args, **kwargs): n = args[0] force = kwargs.get('force', False) if not 1 <= n <= obj.number_of_images(force=force): raise ValueError('Page {} not in file {} [{}-{}]' .format(int(n), obj.file, int(n), int(obj.number_of_images()))) return fn(obj, *args, **kwargs) return wrapper
[docs] @check_cache def number_of_images(self, force: bool = False): """ Return the number of images in the djvu file. :param force: if True, refresh the cached data """ if not hasattr(self, '_page_count'): res, stdoutdata = _call_cmd(['djvused', '-e', 'n', self.file]) if not res: return False self._page_count = int(stdoutdata) return self._page_count
[docs] @check_page_number def page_info(self, n: int, force: bool = False): """ Return a tuple (id, (size, dpi)) for page n of djvu file. :param n: page n of djvu file :param force: if True, refresh the cached data """ if not hasattr(self, '_page_info') or force: self._get_page_info(force=force) return self._page_info[n]
@check_cache def _get_page_info(self, force: bool = False): """ Return a dict of tuples (id, (size, dpi)) for all pages of djvu file. :param force: if True, refresh the cached data """ if not hasattr(self, '_page_info'): self._page_info = {} res, stdoutdata = _call_cmd(['djvudump', self.file]) if not res: return False has_text = False for line in stdoutdata.decode('utf-8').split('\n'): if 'TXTz' in line: has_text = True if 'FORM:DJVU' in line: m = self._pat_form.search(line) if m: key, id = int(m['n']), m['id'] else: # If djvu doc has only one page, # FORM:DJVU line in djvudump has no id key, id = 1, '' if 'INFO' in line: m = self._pat_info.search(line) if m: size, dpi = m['size'], int(m['dpi']) else: size, dpi = None, None else: continue self._page_info[key] = (id, (size, dpi)) self._has_text = has_text return self._page_info
[docs] def get_most_common_info(self): """Return most common size and dpi for pages in djvu file.""" cnt = Counter(s_d for _, s_d in self._get_page_info().values()) (size, dpi), _ = cnt.most_common()[0] return size, dpi
[docs] @check_cache def has_text(self, force: bool = False): """ Test if the djvu file has a text-layer. :param force: if True, refresh the cached data """ if not hasattr(self, '_has_text'): self._get_page_info(force=force) return self._has_text
@staticmethod def _remove_control_chars(data): """Remove djvu format control characters. See http://djvu.sourceforge.net/doc/man/djvused.html for control chars. :param data: the data checked for djvu format control characters """ txt = data.decode('utf-8') # vertical tab (\013=\x0b): remove txt = txt.replace('\x0b', '') # group (\035=\x1d) separator: replace with \n txt = txt.replace('\x1d', '\n') # unit separator (\037=\x1f): replace with \n txt = txt.replace('\x1f', '\n') # feed char (\f=\x0c), \n and trailing spaces: strip txt = txt.strip('\x0c\n ') return txt
[docs] @check_page_number @check_cache def get_page(self, n: int, force: bool = False): """ Get page n for djvu file. :param n: page n of djvu file :param force: if True, refresh the cached data """ if not self.has_text(force=force): raise ValueError(f'Djvu file {self.file} has no text layer.') res, stdoutdata = _call_cmd(['djvutxt', f'--page={n}', self.file]) if not res: return False return self._remove_control_chars(stdoutdata)
[docs] @check_page_number def whiten_page(self, n) -> bool: """Replace page 'n' of djvu file with a blank page. :param n: page n of djvu file :type n: int """ # tmp files for creation/insertion of a white page. white_ppm = os.path.join(self.dirname, 'white_page.ppm') white_djvu = os.path.join(self.dirname, 'white_page.djvu') n_tot = self.number_of_images() # Check n is in valid range and set ref_page number for final checks. ref_page = 2 if n == 1 else n - 1 size, dpi = self.get_most_common_info() # Generate white_page. res, _ = _call_cmd(['convert', '-size', size, 'xc:white', white_ppm], lib='ImageMagik') if not res: return False # Convert white_page to djvu. res, data = _call_cmd(['c44', white_ppm, '-dpi', str(dpi)]) os.unlink(white_ppm) # rm white_page.ppm before returning. if not res: return False # Delete page n. # Get ref page info for later checks. info_ref_page = self.page_info(ref_page) res, data = _call_cmd(['djvm', '-d', self.file, str(n)]) if not res: return False # Insert new page res, data = _call_cmd(['djvm', '-i', self.file, white_djvu, str(n)]) os.unlink(white_djvu) # rm white_page.djvu before returning. if not res: return False # Check if page processing is as expected. expected_id = '{%s}' % os.path.basename(white_djvu) assert self.number_of_images(force=True) == n_tot assert self.page_info(n) == (expected_id, (size, dpi)) # white page id assert self.page_info(ref_page) == info_ref_page # ref page info. return True
[docs] @check_page_number def delete_page(self, n) -> bool: """Delete page 'n' of djvu file. :param n: page n of djvu file :type n: int """ n_tot = self.number_of_images() # Check n is in valid range and set ref_page number for final checks. ref_page = n - 1 if n == n_tot else n + 1 new_ref_page = n - 1 if n == n_tot else n # Delete page n. # Get ref page info for later checks. info_ref_page = self.page_info(ref_page) res, _ = _call_cmd(['djvm', '-d', self.file, str(n)]) if not res: return False # Check if page processing is as expected. # ref page info. if n_tot > 2: assert self.number_of_images(force=True) == n_tot - 1 # cache cleared above assert self.page_info(new_ref_page) == info_ref_page else: # If djvu has only one page, FORM:DJVU line in djvudump has no id _id, (sz, dpi) = info_ref_page assert self.page_info(new_ref_page, force=True) == ('', (sz, dpi)) return True
# This is to be used only if this class is subclassed and the decorators # needs to be used by the child. check_page_number = staticmethod(check_page_number) check_cache = staticmethod(check_cache)