mirror of
https://github.com/paperless-ngx/paperless-ngx.git
synced 2025-04-29 11:09:27 -05:00
completely reworked the OCRmyPDF parser.
This commit is contained in:
jonaswinkler
parent
ebdfd4241a
commit
ce121a261d
@ -41,6 +41,10 @@
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#PAPERLESS_OCR_OUTPUT_TYPE=pdfa
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#PAPERLESS_OCR_PAGES=1
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#PAPERLESS_OCR_IMAGE_DPI=300
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#PAPERLESS_OCR_CLEAN=clean
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#PAPERLESS_OCR_DESKEW=false
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#PAPERLESS_OCR_ROTATE_PAGES=false
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#PAPERLESS_OCR_ROTATE_PAGES_THRESHOLD=10
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#PAPERLESS_OCR_USER_ARGS={}
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#PAPERLESS_CONVERT_MEMORY_LIMIT=0
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#PAPERLESS_CONVERT_TMPDIR=/var/tmp/paperless
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@ -449,6 +449,14 @@ OCR_MODE = os.getenv("PAPERLESS_OCR_MODE", "skip")
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OCR_IMAGE_DPI = os.getenv("PAPERLESS_OCR_IMAGE_DPI")
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OCR_CLEAN = os.getenv("PAPERLESS_OCR_CLEAN", "clean")
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OCR_DESKEW = __get_boolean("PAPERLESS_OCR_DESKEW")
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OCR_ROTATE_PAGES = __get_boolean("PAPERLESS_OCR_ROTATE_PAGES")
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OCR_ROTATE_PAGES_THRESHOLD = float(os.getenv("PAPERLESS_OCR_ROTATE_PAGES_THRESHOLD", 10.0))
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OCR_USER_ARGS = os.getenv("PAPERLESS_OCR_USER_ARGS", "{}")
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# GNUPG needs a home directory for some reason
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@ -9,6 +9,10 @@ from documents.parsers import DocumentParser, ParseError, \
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make_thumbnail_from_pdf
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class NoTextFoundException(Exception):
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pass
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class RasterisedDocumentParser(DocumentParser):
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"""
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This parser uses Tesseract to try and get some text out of a rasterised
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@ -18,12 +22,13 @@ class RasterisedDocumentParser(DocumentParser):
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logging_name = "paperless.parsing.tesseract"
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def extract_metadata(self, document_path, mime_type):
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import pikepdf
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namespace_pattern = re.compile(r"\{(.*)\}(.*)")
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result = []
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if mime_type == 'application/pdf':
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import pikepdf
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namespace_pattern = re.compile(r"\{(.*)\}(.*)")
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pdf = pikepdf.open(document_path)
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meta = pdf.open_metadata()
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for key, value in meta.items():
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@ -88,125 +93,199 @@ class RasterisedDocumentParser(DocumentParser):
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f"Error while calculating DPI for image {image}: {e}")
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return None
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def extract_text(self, sidecar_file, pdf_file):
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if sidecar_file and os.path.isfile(sidecar_file):
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with open(sidecar_file, "r") as f:
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text = f.read()
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if "[OCR skipped on page" not in text:
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# This happens when there's already text in the input file.
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# The sidecar file will only contain text for OCR'ed pages.
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self.log("debug", "Using text from sidecar file")
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return text
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else:
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self.log("debug", "Incomplete sidecar file: discarding.")
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# no success with the sidecar file, try PDF
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if not os.path.isfile(pdf_file):
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return None
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from pdfminer.high_level import extract_text
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from pdfminer.pdftypes import PDFException
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try:
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text = extract_text(pdf_file)
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stripped = strip_excess_whitespace(text)
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self.log("debug", f"Extracted text from PDF file {pdf_file}")
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return stripped
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except PDFException:
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# probably not a PDF file.
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return None
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def construct_ocrmypdf_parameters(self,
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input_file,
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mime_type,
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output_file,
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sidecar_file,
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safe_fallback=False):
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ocrmypdf_args = {
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'input_file': input_file,
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'output_file': output_file,
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# need to use threads, since this will be run in daemonized
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# processes by django-q.
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'use_threads': True,
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'jobs': settings.THREADS_PER_WORKER,
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'language': settings.OCR_LANGUAGE,
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'output_type': settings.OCR_OUTPUT_TYPE,
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'progress_bar': False
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}
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if settings.OCR_MODE == 'force' or safe_fallback:
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ocrmypdf_args['force_ocr'] = True
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elif settings.OCR_MODE in ['skip', 'skip_noarchive']:
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ocrmypdf_args['skip_text'] = True
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elif settings.OCR_MODE == 'redo':
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ocrmypdf_args['redo_ocr'] = True
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else:
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raise ParseError(
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f"Invalid ocr mode: {settings.OCR_MODE}")
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if settings.OCR_CLEAN == 'clean':
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ocrmypdf_args['clean'] = True
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elif settings.OCR_CLEAN == 'clean-final':
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ocrmypdf_args['clean_final'] = True
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if settings.OCR_DESKEW:
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ocrmypdf_args['deskew'] = True
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if settings.OCR_ROTATE_PAGES:
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ocrmypdf_args['rotate_pages'] = True
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ocrmypdf_args['rotate_pages_threshold'] = settings.OCR_ROTATE_PAGES_THRESHOLD # NOQA: E501
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if settings.OCR_PAGES > 0:
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ocrmypdf_args['pages'] = f"1-{settings.OCR_PAGES}"
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else:
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# sidecar is incompatible with pages
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ocrmypdf_args['sidecar'] = sidecar_file
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if self.is_image(mime_type):
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dpi = self.get_dpi(input_file)
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a4_dpi = self.calculate_a4_dpi(input_file)
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if dpi:
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self.log(
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"debug",
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f"Detected DPI for image {input_file}: {dpi}"
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)
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ocrmypdf_args['image_dpi'] = dpi
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elif settings.OCR_IMAGE_DPI:
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ocrmypdf_args['image_dpi'] = settings.OCR_IMAGE_DPI
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elif a4_dpi:
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ocrmypdf_args['image_dpi'] = a4_dpi
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else:
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raise ParseError(
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f"Cannot produce archive PDF for image {input_file}, "
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f"no DPI information is present in this image and "
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f"OCR_IMAGE_DPI is not set.")
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if settings.OCR_USER_ARGS and not safe_fallback:
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try:
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user_args = json.loads(settings.OCR_USER_ARGS)
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ocrmypdf_args = {**ocrmypdf_args, **user_args}
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except Exception as e:
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self.log(
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"warning",
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f"There is an issue with PAPERLESS_OCR_USER_ARGS, so "
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f"they will not be used. Error: {e}")
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return ocrmypdf_args
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def parse(self, document_path, mime_type, file_name=None):
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import ocrmypdf
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from ocrmypdf import InputFileError, EncryptedPdfError
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# This forces tesseract to use one core per page.
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os.environ['OMP_THREAD_LIMIT'] = "1"
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mode = settings.OCR_MODE
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text_original = self.extract_text(None, document_path)
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original_has_text = text_original and len(text_original) > 50
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text_original = get_text_from_pdf(document_path)
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has_text = text_original and len(text_original) > 50
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if mode == "skip_noarchive" and has_text:
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if settings.OCR_MODE == "skip_noarchive" and original_has_text:
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self.log("debug",
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"Document has text, skipping OCRmyPDF entirely.")
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self.text = text_original
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return
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if mode in ['skip', 'skip_noarchive'] and not has_text:
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# upgrade to redo, since there appears to be no text in the
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# document. This happens to some weird encrypted documents or
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# documents with failed OCR attempts for which OCRmyPDF will
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# still report that there actually is text in them.
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self.log("debug",
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"No text was found in the document and skip is "
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"specified. Upgrading OCR mode to redo.")
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mode = "redo"
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import ocrmypdf
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from ocrmypdf import InputFileError, EncryptedPdfError
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archive_path = os.path.join(self.tempdir, "archive.pdf")
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sidecar_file = os.path.join(self.tempdir, "sidecar.txt")
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ocr_args = {
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'input_file': document_path,
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'output_file': archive_path,
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'use_threads': True,
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'jobs': settings.THREADS_PER_WORKER,
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'language': settings.OCR_LANGUAGE,
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'output_type': settings.OCR_OUTPUT_TYPE,
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'progress_bar': False,
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'clean': True
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}
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if settings.OCR_PAGES > 0:
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ocr_args['pages'] = f"1-{settings.OCR_PAGES}"
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# Mode selection.
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if mode in ['skip', 'skip_noarchive']:
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ocr_args['skip_text'] = True
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elif mode == 'redo':
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ocr_args['redo_ocr'] = True
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elif mode == 'force':
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ocr_args['force_ocr'] = True
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else:
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raise ParseError(
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f"Invalid ocr mode: {mode}")
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if self.is_image(mime_type):
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dpi = self.get_dpi(document_path)
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a4_dpi = self.calculate_a4_dpi(document_path)
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if dpi:
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self.log(
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"debug",
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f"Detected DPI for image {document_path}: {dpi}"
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)
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ocr_args['image_dpi'] = dpi
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elif settings.OCR_IMAGE_DPI:
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ocr_args['image_dpi'] = settings.OCR_IMAGE_DPI
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elif a4_dpi:
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ocr_args['image_dpi'] = a4_dpi
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else:
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raise ParseError(
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f"Cannot produce archive PDF for image {document_path}, "
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f"no DPI information is present in this image and "
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f"OCR_IMAGE_DPI is not set.")
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if settings.OCR_USER_ARGS:
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try:
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user_args = json.loads(settings.OCR_USER_ARGS)
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ocr_args = {**ocr_args, **user_args}
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except Exception as e:
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self.log(
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"warning",
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f"There is an issue with PAPERLESS_OCR_USER_ARGS, so "
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f"they will not be used: {e}")
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# This forces tesseract to use one core per page.
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os.environ['OMP_THREAD_LIMIT'] = "1"
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args = self.construct_ocrmypdf_parameters(
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document_path, mime_type, archive_path, sidecar_file)
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try:
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self.log("debug",
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f"Calling OCRmyPDF with {str(ocr_args)}")
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ocrmypdf.ocr(**ocr_args)
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# success! announce results
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self.log("debug", f"Calling OCRmyPDF with args: {args}")
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ocrmypdf.ocr(**args)
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self.archive_path = archive_path
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self.text = get_text_from_pdf(archive_path)
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self.text = self.extract_text(sidecar_file, archive_path)
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except (InputFileError, EncryptedPdfError) as e:
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self.log("debug",
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f"Encountered an error: {e}. Trying to use text from "
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f"original.")
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# This happens with some PDFs when used with the redo_ocr option.
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# This is not the end of the world, we'll just use what we already
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# have in the document.
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self.text = text_original
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# Also, no archived file.
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if not self.text:
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# However, if we don't have anything, fail:
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raise NoTextFoundException(
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"No text was found in the original document")
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except EncryptedPdfError:
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self.log("warning",
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"This file is encrypted, OCR is impossible. Using "
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"any text present in the original file.")
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if original_has_text:
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self.text = text_original
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except (NoTextFoundException, InputFileError) as e:
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self.log("exception",
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f"Encountered the following error while running OCR, "
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f"attempting force OCR to get the text.")
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archive_path_fallback = os.path.join(
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self.tempdir, "archive-fallback.pdf")
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sidecar_file_fallback = os.path.join(
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self.tempdir, "sidecar-fallback.txt")
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# Attempt to run OCR with safe settings.
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args = self.construct_ocrmypdf_parameters(
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document_path, mime_type,
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archive_path_fallback, sidecar_file_fallback,
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safe_fallback=True
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)
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try:
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self.log("debug",
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f"Fallback: Calling OCRmyPDF with args: {args}")
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ocrmypdf.ocr(**args)
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# Don't return the archived file here, since this file
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# is bigger and blurry due to --force-ocr.
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self.text = self.extract_text(
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sidecar_file_fallback, archive_path_fallback)
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except Exception as e:
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# If this fails, we have a serious issue at hand.
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raise ParseError(f"{e.__class__.__name__}: {str(e)}")
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except Exception as e:
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# Anything else is probably serious.
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raise ParseError(f"{e.__class__.__name__}: {str(e)}")
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# As a last resort, if we still don't have any text for any reason,
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# try to extract the text from the original document.
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if not self.text:
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# This may happen for files that don't have any text.
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self.log(
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'warning',
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f"Document {document_path} does not have any text. "
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f"This is probably an error or you tried to add an image "
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f"without text, or something is wrong with this document.")
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self.text = ""
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if original_has_text:
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self.text = text_original
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else:
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self.log(
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"warning",
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f"No text was found in {document_path}, the content will "
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f"be empty."
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)
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def strip_excess_whitespace(text):
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@ -222,20 +301,3 @@ def strip_excess_whitespace(text):
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# TODO: this needs a rework
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return no_trailing_whitespace.strip()
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def get_text_from_pdf(pdf_file):
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import pdftotext
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if not os.path.isfile(pdf_file):
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return None
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with open(pdf_file, "rb") as f:
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try:
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pdf = pdftotext.PDF(f)
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except pdftotext.Error:
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# might not be a PDF file
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return None
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text = "\n".join(pdf)
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return strip_excess_whitespace(text)
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