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Add unpaper as another pre-processing step

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This commit is contained in:
Pit Kleyersburg 2016-02-16 10:49:55 +01:00
parent 0e2d8cc0d8
commit fb36a49c26
5 changed files with 53 additions and 36 deletions
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2
Dockerfile
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@ -5,7 +5,7 @@ MAINTAINER Pit Kleyersburg <pitkley@googlemail.com>
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
sudo \
tesseract-ocr tesseract-ocr-eng imagemagick ghostscript \
tesseract-ocr tesseract-ocr-eng imagemagick ghostscript unpaper \
&& rm -rf /var/lib/apt/lists/*
# Install python dependencies

2
docs/requirements.rst
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@ -10,11 +10,13 @@ should work) that has the following software installed on it:
* `GNU Privacy Guard`_
* `Tesseract`_
* `Imagemagick`_
* `unpaper`_
.. _Python3: https://python.org/
.. _GNU Privacy Guard: https://gnupg.org
.. _Tesseract: https://github.com/tesseract-ocr
.. _Imagemagick: http://imagemagick.org/
.. _unpaper: https://www.flameeyes.eu/projects/unpaper
Notably, you should confirm how you access your Python3 installation. Many
Linux distributions will install Python3 in parallel to Python2, using the names

2
scripts/vagrant-provision
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@ -5,7 +5,7 @@ apt-get update
apt-get build-dep -y python-imaging
apt-get install -y libjpeg8 libjpeg62-dev libfreetype6 libfreetype6-dev
apt-get install -y build-essential python3-dev python3-pip sqlite3 libsqlite3-dev git
apt-get install -y tesseract-ocr tesseract-ocr-eng imagemagick
apt-get install -y tesseract-ocr tesseract-ocr-eng imagemagick unpaper
# Python dependencies
pip3 install -r /opt/paperless/requirements.txt

80
src/documents/consumer.py
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@ -39,8 +39,8 @@ class ConsumerError(Exception):
class Consumer(object):
"""
Loop over every file found in CONSUMPTION_DIR and:
1. Convert it to a greyscale png
2. Use tesseract on the png
1. Convert it to a greyscale pnm
2. Use tesseract on the pnm
3. Encrypt and store the document in the MEDIA_ROOT
4. Store the OCR'd text in the database
5. Delete the document and image(s)
@ -48,6 +48,7 @@ class Consumer(object):
SCRATCH = settings.SCRATCH_DIR
CONVERT = settings.CONVERT_BINARY
UNPAPER = settings.UNPAPER_BINARY
CONSUME = settings.CONSUMPTION_DIR
THREADS = int(settings.OCR_THREADS) if settings.OCR_THREADS else None
@ -118,11 +119,11 @@ class Consumer(object):
self.log("info", "Consuming {}".format(doc))
tempdir = tempfile.mkdtemp(prefix="paperless", dir=self.SCRATCH)
pngs = self._get_greyscale(tempdir, doc)
imgs = self._get_greyscale(tempdir, doc)
thumbnail = self._get_thumbnail(tempdir, doc)
try:
text = self._get_ocr(pngs)
text = self._get_ocr(imgs)
self._store(text, doc, thumbnail)
except OCRError as e:
self._ignore.append(doc)
@ -140,19 +141,30 @@ class Consumer(object):
self.log("info", "Generating greyscale image from {}".format(doc))
png = os.path.join(tempdir, "convert-%04d.jpg")
# Convert PDF to multiple PNMs
pnm = os.path.join(tempdir, "convert-%04d.pnm")
subprocess.Popen((
self.CONVERT, "-density", "300", "-depth", "8",
"-type", "grayscale", doc, png
"-type", "grayscale", doc, pnm
)).wait()
pngs = []
# Get a list of converted images
pnms = []
for f in os.listdir(tempdir):
if f.startswith("convert"):
pngs.append(os.path.join(tempdir, f))
if f.endswith(".pnm"):
pnms.append(os.path.join(tempdir, f))
return sorted(filter(lambda __: os.path.isfile(__), pngs))
# Run unpaper in parallel on converted images
with Pool(processes=self.THREADS) as pool:
pool.map(run_unpaper, itertools.product([self.UNPAPER], pnms))
# Return list of converted images, processed with unpaper
pnms = []
for f in os.listdir(tempdir):
if f.endswith(".unpaper.pnm"):
pnms.append(os.path.join(tempdir, f))
return sorted(filter(lambda __: os.path.isfile(__), pnms))
def _get_thumbnail(self, tempdir, doc):
"""
@ -179,21 +191,21 @@ class Consumer(object):
except Exception as e:
self.log("warning", "Language detection error: {}".format(e))
def _get_ocr(self, pngs):
def _get_ocr(self, imgs):
"""
Attempts to do the best job possible OCR'ing the document based on
simple language detection trial & error.
"""
if not pngs:
if not imgs:
raise OCRError("No images found")
self.log("info", "OCRing the document")
# Since the division gets rounded down by int, this calculation works
# for every edge-case, i.e. 1
middle = int(len(pngs) / 2)
raw_text = self._ocr([pngs[middle]], self.DEFAULT_OCR_LANGUAGE)
middle = int(len(imgs) / 2)
raw_text = self._ocr([imgs[middle]], self.DEFAULT_OCR_LANGUAGE)
guessed_language = self._guess_language(raw_text)
@ -205,16 +217,16 @@ class Consumer(object):
"As FORGIVING_OCR is enabled, we're going to make the "
"best with what we have."
)
raw_text = self._assemble_ocr_sections(pngs, middle, raw_text)
raw_text = self._assemble_ocr_sections(imgs, middle, raw_text)
return raw_text
raise OCRError("Language detection failed")
if ISO639[guessed_language] == self.DEFAULT_OCR_LANGUAGE:
raw_text = self._assemble_ocr_sections(pngs, middle, raw_text)
raw_text = self._assemble_ocr_sections(imgs, middle, raw_text)
return raw_text
try:
return self._ocr(pngs, ISO639[guessed_language])
return self._ocr(imgs, ISO639[guessed_language])
except pyocr.pyocr.tesseract.TesseractError:
if settings.FORGIVING_OCR:
self.log(
@ -224,34 +236,34 @@ class Consumer(object):
guessed_language
)
)
raw_text = self._assemble_ocr_sections(pngs, middle, raw_text)
raw_text = self._assemble_ocr_sections(imgs, middle, raw_text)
return raw_text
raise OCRError(
"The guessed language is not available in this instance of "
"Tesseract."
)
def _assemble_ocr_sections(self, pngs, middle, text):
def _assemble_ocr_sections(self, imgs, middle, text):
"""
Given a `middle` value and the text that middle page represents, we OCR
the remainder of the document and return the whole thing.
"""
text = self._ocr(pngs[:middle], self.DEFAULT_OCR_LANGUAGE) + text
text += self._ocr(pngs[middle+1:], self.DEFAULT_OCR_LANGUAGE)
text = self._ocr(imgs[:middle], self.DEFAULT_OCR_LANGUAGE) + text
text += self._ocr(imgs[middle + 1:], self.DEFAULT_OCR_LANGUAGE)
return text
def _ocr(self, pngs, lang):
def _ocr(self, imgs, lang):
"""
Performs a single OCR attempt.
"""
if not pngs:
if not imgs:
return ""
self.log("info", "Parsing for {}".format(lang))
with Pool(processes=self.THREADS) as pool:
r = pool.map(image_to_string, itertools.product(pngs, [lang]))
r = pool.map(image_to_string, itertools.product(imgs, [lang]))
r = " ".join(r)
# Strip out excess white space to allow matching to go smoother
@ -374,16 +386,9 @@ class Consumer(object):
def image_to_string(args):
"""
I have no idea why, but if this function were a method of Consumer, it
would explode with:
`TypeError: cannot serialize '_io.TextIOWrapper' object`.
"""
png, lang = args
img, lang = args
ocr = pyocr.get_available_tools()[0]
with Image.open(os.path.join(Consumer.SCRATCH, png)) as f:
with Image.open(os.path.join(Consumer.SCRATCH, img)) as f:
if ocr.can_detect_orientation():
try:
orientation = ocr.detect_orientation(f, lang=lang)
@ -391,3 +396,10 @@ def image_to_string(args):
except TesseractError:
pass
return ocr.image_to_string(f, lang=lang)
def run_unpaper(args):
unpaper, pnm = args
subprocess.Popen((
unpaper, pnm, pnm.replace(".pnm", ".unpaper.pnm")
)).wait()

3
src/paperless/settings.py
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@ -189,6 +189,9 @@ GNUPG_HOME = os.getenv("HOME", "/tmp")
# Convert is part of the ImageMagick package
CONVERT_BINARY = os.getenv("PAPERLESS_CONVERT_BINARY")
# Unpaper
UNPAPER_BINARY = os.getenv("PAPERLESS_UNPAPER_BINARY", "unpaper")
# This will be created if it doesn't exist
SCRATCH_DIR = os.getenv("PAPERLESS_SCRATCH_DIR", "/tmp/paperless")