#!/usr/bin/env python3
# © 2015 James R. Barlow: github.com/jbarlow83
import sys
import os
import re
import shutil
from functools import lru_cache
from . import ExitCode, get_program
from subprocess import Popen, PIPE, CalledProcessError, \
TimeoutExpired, check_output, STDOUT
try:
from subprocess import DEVNULL
except ImportError:
DEVNULL = open(os.devnull, 'wb')
HOCR_TEMPLATE = '''
'''
@lru_cache(maxsize=1)
def version():
args_tess = [
get_program('tesseract'),
'--version'
]
try:
versions = check_output(
args_tess, close_fds=True, universal_newlines=True,
stderr=STDOUT)
except CalledProcessError:
print("Could not find Tesseract executable on system PATH.")
sys.exit(ExitCode.missing_dependency)
tesseract_version = re.match(r'tesseract\s(.+)', versions).group(1)
return tesseract_version
@lru_cache(maxsize=1)
def languages():
args_tess = [
get_program('tesseract'),
'--list-langs'
]
try:
langs = check_output(
args_tess, close_fds=True, universal_newlines=True,
stderr=STDOUT)
except CalledProcessError as e:
print("Tesseract failed to report available languages.")
print("Output from Tesseract:")
print("-" * 40)
print(e.output)
sys.exit(ExitCode.missing_dependency)
return set(lang.strip() for lang in langs.splitlines()[1:])
def generate_hocr(input_file, output_hocr, language: list, tessconfig: list,
timeout: float, pageinfo_getter, pagesegmode: int, log):
badxml = os.path.splitext(output_hocr)[0] + '.badxml'
args_tesseract = [
get_program('tesseract'),
'-l', '+'.join(language)
]
if pagesegmode is not None:
args_tesseract.extend(['-psm', str(pagesegmode)])
args_tesseract.extend([
input_file,
badxml,
'hocr'
] + tessconfig)
p = Popen(args_tesseract, close_fds=True, stdout=PIPE, stderr=PIPE,
universal_newlines=True)
try:
stdout, stderr = p.communicate(timeout=timeout)
except TimeoutExpired:
p.kill()
stdout, stderr = p.communicate()
# Generate a HOCR file with no recognized text if tesseract times out
# Temporary workaround to hocrTransform not being able to function if
# it does not have a valid hOCR file.
with open(output_hocr, 'w', encoding="utf-8") as f:
pageinfo = pageinfo_getter()
f.write(HOCR_TEMPLATE.format(
pageinfo['width_pixels'],
pageinfo['height_pixels']))
else:
if stdout:
log.info(stdout)
if stderr:
log.error(stderr)
if p.returncode != 0:
raise CalledProcessError(p.returncode, args_tesseract)
if os.path.exists(badxml + '.html'):
# Tesseract 3.02 appends suffix ".html" on its own (.badxml.html)
shutil.move(badxml + '.html', badxml)
elif os.path.exists(badxml + '.hocr'):
# Tesseract 3.03 appends suffix ".hocr" on its own (.badxml.hocr)
shutil.move(badxml + '.hocr', badxml)
# Tesseract 3.03 inserts source filename into hocr file without
# escaping it, creating invalid XML and breaking the parser.
# As a workaround, rewrite the hocr file, replacing the filename
# with a space. Don't know if Tesseract 3.02 does the same.
regex_nested_single_quotes = re.compile(
r"""title='image "([^"]*)";""")
with open(badxml, mode='r', encoding='utf-8') as f_in, \
open(output_hocr, mode='w', encoding='utf-8') as f_out:
for line in f_in:
line = regex_nested_single_quotes.sub(
r"""title='image " ";""", line)
f_out.write(line)
def generate_pdf(input_image, skip_pdf, output_pdf, language: list,
tessconfig: list, timeout: float, pagesegmode: int, log):
'''Use Tesseract to render a PDF.
input_image -- image to analyze
skip_pdf -- if we time out, use this file as output
language -- list of languages to consider
tessconfig -- tesseract configuration
timeout -- timeout (seconds)
log -- logger object
'''
args_tesseract = [
get_program('tesseract'),
'-l', '+'.join(language)
]
if pagesegmode is not None:
args_tesseract.extend(['-psm', str(pagesegmode)])
args_tesseract.extend([
input_image,
os.path.splitext(output_pdf)[0], # Tesseract appends suffix
'pdf'
] + tessconfig)
p = Popen(args_tesseract, close_fds=True, stdout=PIPE, stderr=PIPE,
universal_newlines=True)
try:
stdout, stderr = p.communicate(timeout=timeout)
if stdout:
log.info(stdout)
if stderr:
log.error(stderr)
except TimeoutExpired:
p.kill()
log.info("Tesseract - page timed out")
shutil.copy(skip_pdf, output_pdf)