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pypdfocr_gs.py
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pypdfocr_gs.py
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#!/usr/bin/env python2.7
# Copyright 2013 Virantha Ekanayake All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Wrap ghostscript calls. Yes, this is ugly.
"""
import subprocess
import sys, os
import logging
import glob
def error(text):
print("ERROR: %s" % text)
exit(-1)
class PyGs(object):
"""Class to wrap all the ghostscript calls"""
def __init__(self, config):
self.msgs = {
'GS_FAILED': 'Ghostscript execution failed',
'GS_MISSING_PDF': 'Cannot find specified pdf file',
'GS_OUTDATED': 'Your Ghostscript version is probably out of date. Please upgrade to the latest version',
'GS_MISSING_BINARY': 'Could not find Ghostscript in the usual place; please specify it using your config file',
}
self.threads = config.get('threads',4)
if "binary" in config: # Override location of binary
binary = config['binary']
if os.name == 'nt':
binary = '"%s"' % binary
binary = binary.replace("\\", "\\\\")
logging.info("Setting location for executable to %s" % (binary))
else:
if str(os.name) == 'nt':
win_binary = self._find_windows_gs()
binary = '"%s"' % win_binary
logging.info("Using Ghostscript: %s" % binary)
else:
binary = "gs"
self.binary = binary
#self.tiff_dpi = 300
self.output_dpi = 300
self.greyscale = True
# Tiff is used for the ocr, so just fix it at 300dpi
# The other formats will be used to create the final OCR'ed image, so determine
# the DPI by using pdfimages if available, o/w default to 200
self.gs_options = {'tiff': ['tiff', ['-sDEVICE=tiff24nc','-r%(dpi)s' ]],
'jpg': ['jpg', ['-sDEVICE=jpeg','-dJPEGQ=75', '-r%(dpi)s']],
'jpggrey': ['jpg', ['-sDEVICE=jpeggray', '-dJPEGQ=75', '-r%(dpi)s']],
'png': ['png', ['-sDEVICE=png16m', '-r%(dpi)s']],
'pnggrey': ['png', ['-sDEVICE=pngmono', '-r%(dpi)s']],
'tifflzw': ['tiff', ['-sDEVICE=tifflzw', '-r%(dpi)s']],
'tiffg4': ['tiff', ['-sDEVICE=tiffg4', '-r%(dpi)s']],
'pnm': ['pnm', ['-sDEVICE=pnmraw', '-r%(dpi)s']],
'pgm': ['pgm', ['-sDEVICE=pgm', '-r%(dpi)s']],
}
def _find_windows_gs(self):
"""
Searches through the Windows program files directories to find Ghostscript.
If it finds multiple versions, it does a naive sort for now to find the most
recent.
:rval: The ghostscript binary location
"""
windirs = ["c:\\Program Files\\gs", "c:\\Program Files (x86)\\gs"]
gs = None
for d in windirs:
if not os.path.exists(d):
continue
cwd = os.getcwd()
os.chdir(d)
listing = os.listdir('.')
# Find all possible gs* sub-directories
listing = [x for x in listing if x.startswith('gs')]
# TODO: Make this a natural sort
listing.sort(reverse=True)
for bindir in listing:
binpath = os.path.join(bindir,'bin')
if not os.path.exists(binpath): continue
os.chdir(binpath)
# Look for gswin64c.exe or gswin32c.exe (the c is for the command-line version)
gswin = glob.glob('gswin*c.exe')
if len(gswin) == 0:
continue
gs = os.path.abspath(gswin[0]) # Just use the first found .exe (Do i need to do anything more complicated here?)
os.chdir(cwd)
return gs
if not gs:
error(self.msgs['GS_MISSING_BINARY'])
def _warn(self, msg):
print("WARNING: %s" % msg)
def _get_dpi(self, pdf_filename):
if not os.path.exists(pdf_filename):
error(self.msgs['GS_MISSING_PDF'] + " %s" % pdf_filename)
cmd = 'pdfimages -list "%s"' % pdf_filename
logging.info("Running pdfimages to figure out DPI...")
logging.debug(cmd)
try:
out = subprocess.check_output(cmd, shell=True)
except subprocess.CalledProcessError as e:
self._warn ("Could not execute pdfimages to calculate DPI (try installing xpdf or poppler?), so defaulting to %sdpi" % self.output_dpi)
return
# Need the second line of output
# Make sure it exists (in case this is an empty pdf)
results = out.splitlines()
if len(results)<3:
self._warn("Empty pdf, cannot determine dpi using pdfimages")
return
results = results[2]
logging.debug(results)
results = results.split()
if(results[2] != 'image'):
self._warn("Could not understand output of pdfimages, please rerun with -d option and file an issue at http://github.com/virantha/pypdfocr/issues")
return
x_pt, y_pt, greyscale = int(results[3]), int(results[4]), results[5]=='gray'
self.greyscale = greyscale
# Now, run imagemagick identify to get pdf width/height/density
cmd = 'identify -format "%%w %%x %%h %%y\n" "%s"' % pdf_filename
try:
out = subprocess.check_output(cmd, shell=True)
results = out.splitlines()[0]
results = results.replace("Undefined", "")
width, xdensity, height, ydensity = [float(x) for x in results.split()]
xdpi = round(x_pt/width*xdensity)
ydpi = round(y_pt/height*ydensity)
self.output_dpi = xdpi
if ydpi>xdpi: self.output_dpi = ydpi
if self.output_dpi < 300: self.output_dpi = 300
if abs(xdpi-ydpi) > xdpi*.05: # Make sure the two dpi's are within 5%
self._warn("X-dpi is %d, Y-dpi is %d, defaulting to %d" % (xdpi, ydpi, self.output_dpi))
else:
print("Using %d DPI" % self.output_dpi)
except Exception as e:
logging.debug(str(e))
self._warn ("Could not execute identify to calculate DPI (try installing imagemagick?), so defaulting to %sdpi" % self.output_dpi)
return
def _run_gs(self, options, output_filename, pdf_filename):
try:
cmd = '%s -q -dNOPAUSE %s -sOutputFile="%s" "%s" -c quit' % (self.binary, options, output_filename, pdf_filename)
logging.info(cmd)
out = subprocess.check_output(cmd, shell=True)
except subprocess.CalledProcessError as e:
print e.output
if "undefined in .getdeviceparams" in e.output:
error(self.msgs['GS_OUTDATED'])
else:
error (self.msgs['GS_FAILED'])
def make_img_from_pdf(self, pdf_filename):
self._get_dpi(pdf_filename) # No need to bother anymore
if not os.path.exists(pdf_filename):
error(self.msgs['GS_MISSING_PDF'] + " %s" % pdf_filename)
filename, filext = os.path.splitext(pdf_filename)
# Create ancillary jpeg files to use later to calculate image dpi etc
# We no longer use these for the final image. Instead the text is merged
# directly with the original PDF. Yay!
if self.greyscale:
self.img_format = 'jpggrey'
#self.img_format = 'pnggrey'
logging.info("Detected greyscale")
else:
self.img_format = 'jpg'
#self.img_format = 'png'
logging.info("Detected color")
self.img_file_ext = self.gs_options[self.img_format][0]
# The possible output files glob
globable_filename = '%s_*.%s' % (filename, self.img_file_ext)
# Delete any img files already existing
for fn in glob.glob(globable_filename):
os.remove(fn)
options = ' '.join(self.gs_options[self.img_format][1]) % {'dpi':self.output_dpi}
output_filename = '%s_%%d.%s' % (filename, self.img_file_ext)
self._run_gs(options, output_filename, pdf_filename)
for fn in glob.glob(globable_filename):
logging.info("Created image %s" % fn)
return (self.output_dpi, globable_filename)