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OCRmyPDF/ocrmypdf/exec/unpaper.py
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Python

# © 2015 James R. Barlow: github.com/jbarlow83
# unpaper documentation:
# https://github.com/Flameeyes/unpaper/blob/master/doc/basic-concepts.md
from subprocess import CalledProcessError, STDOUT, check_output
from tempfile import NamedTemporaryFile
import sys
import os
from functools import lru_cache
from ..exceptions import MissingDependencyError
from . import get_program, get_version
try:
from PIL import Image
except ImportError:
print("Could not find Python3 imaging library", file=sys.stderr)
raise
@lru_cache(maxsize=1)
def version():
return get_version('unpaper')
def run(input_file, output_file, dpi, log, mode_args):
args_unpaper = [
get_program('unpaper'),
'-v',
'--dpi', str(dpi)
] + mode_args
SUFFIXES = {'1': '.pbm', 'L': '.pgm', 'RGB': '.ppm'}
im = Image.open(input_file)
if im.mode not in SUFFIXES.keys():
log.info("Converting image to other colorspace")
try:
if im.mode == 'P' and len(im.getcolors()) == 2:
im = im.convert(mode='1')
else:
im = im.convert(mode='RGB')
except IOError as e:
log.error(
"Could not convert image with type " + im.mode)
raise MissingDependencyError() from e
try:
suffix = SUFFIXES[im.mode]
except KeyError:
log.error(
"Failed to convert image to a supported format.")
raise MissingDependencyError() from e
with NamedTemporaryFile(suffix=suffix) as input_pnm, \
NamedTemporaryFile(suffix=suffix, mode="r+b") as output_pnm:
im.save(input_pnm, format='PPM')
im.close()
os.unlink(output_pnm.name)
args_unpaper.extend([input_pnm.name, output_pnm.name])
try:
stdout = check_output(
args_unpaper, close_fds=True,
universal_newlines=True, stderr=STDOUT,
)
except CalledProcessError as e:
log.debug(e.output)
raise e from e
else:
log.debug(stdout)
# unpaper sets dpi to 72
Image.open(output_pnm.name).save(output_file, dpi=(dpi, dpi))
def deskew(input_file, output_file, dpi, log):
run(input_file, output_file, dpi, log, [
'--mask-scan-size', '100', # don't blank out narrow columns
'--no-border-align', # don't align visible content to borders
'--no-mask-center', # don't center visible content within page
'--no-grayfilter', # don't remove light gray areas
'--no-blackfilter', # don't remove solid black areas
'--no-noisefilter', # don't remove salt and pepper noise
'--no-blurfilter' # don't remove blurry objects/debris
])
def clean(input_file, output_file, dpi, log):
run(input_file, output_file, dpi, log, [
'--mask-scan-size', '100', # don't blank out narrow columns
'--no-border-align', # don't align visible content to borders
'--no-mask-center', # don't center visible content within page
'--no-grayfilter', # don't remove light gray areas
'--no-blackfilter', # don't remove solid black areas
'--no-deskew', # don't deskew
])