134 lines
4.6 KiB
Python
134 lines
4.6 KiB
Python
# © 2020 James R. Barlow: github.com/jbarlow83
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#
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# This file is part of OCRmyPDF.
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#
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# OCRmyPDF is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# OCRmyPDF is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with OCRmyPDF. If not, see <http://www.gnu.org/licenses/>.
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from abc import ABC, abstractstaticmethod
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from argparse import ArgumentParser, Namespace
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from collections import namedtuple
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from pathlib import Path
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from typing import AbstractSet, Optional
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import pluggy
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from PIL import Image
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hookspec = pluggy.HookspecMarker('ocrmypdf')
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# pylint: disable=unused-argument
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@hookspec
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def add_options(parser: ArgumentParser) -> None:
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"""Allows the plugin to add its own command line arguments.
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Even if you do not intend to use plugins in a command line context, you
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should use this function to create your options.
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"""
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@hookspec
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def prepare(options: Namespace) -> None:
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"""Called to notify a plugin that a file will be processed.
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The plugin may modify the *options*. All objects that are in options must
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be picklable so they can be marshalled to child worker processes.
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"""
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@hookspec
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def validate(pdfinfo: 'PdfInfo', options: Namespace) -> None:
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"""Called to give a plugin an opportunity to review *options* and *pdfinfo*.
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*options* contains the "work order" to process a particular file. *pdfinfo*
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contains information about the input file obtained after loading and
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parsing. The plugin may modify the *options*. For example, you could decide
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that a certain type of file should be treated with ``options.force_ocr = True``
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based on information in its *pdfinfo*.
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The plugin may raise :class:`ocrmypdf.exceptions.InputFileError` or any
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:class:`ocrmypdf.exceptions.ExitCodeException` to request
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normal termination. ocrmypdf will hold the plugin responsible for raising
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exceptions of any other type.
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The return value is ignored. To abort processing, raise an ``ExitCodeException``.
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"""
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@hookspec(firstresult=True)
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def filter_ocr_image(page: 'PageContext', image: Image) -> Image:
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"""Called to filter the image before it is sent to OCR.
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This is the image that OCR sees, not what the user sees when they view the
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PDF.
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"""
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@hookspec(firstresult=True)
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def filter_page_image(page: 'PageContext', image_filename: Path) -> Path:
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"""Called to filter the whole page before it is inserted into the PDF.
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A whole page image is only produced when preprocessing command line arguments
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are issued or when ``--force-ocr`` is issued. If no whole page is image is
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produced for a given page, this function will not be called. This is not
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the image that will be shown to OCR.
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ocrmypdf will create the PDF page based on the image format used. If you
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convert the image to a JPEG, the output page will be created as a JPEG, etc.
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Note that the ocrmypdf image optimization stage may ultimately chose a
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different format.
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"""
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OrientationConfidence = namedtuple('OrientationConfidence', ('angle', 'confidence'))
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class OcrEngine(ABC):
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@abstractstaticmethod
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def version() -> str:
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"""Returns the version of the OCR engine."""
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@abstractstaticmethod
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def creator_tag(options: Namespace) -> str:
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"""Returns the creator tag to identify this software's role in creating the PDF."""
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@abstractstaticmethod
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def __str__(self):
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"""Returns name of OCR engine and version."""
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@abstractstaticmethod
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def languages(options: Namespace) -> AbstractSet[str]:
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"""Returns set of languages that are supported."""
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@abstractstaticmethod
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def get_orientation(input_file: Path, options: Namespace) -> OrientationConfidence:
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"""Returns the orientation of the image."""
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@abstractstaticmethod
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def generate_hocr(
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input_file: Path, output_hocr: Path, output_text: Path, options: Namespace
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) -> None:
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"""Called to produce a hOCR file."""
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@abstractstaticmethod
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def generate_pdf(
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input_file: Path, output_pdf: Path, output_text: Path, options: Namespace
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) -> None:
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"""Called to produce a text only PDF (no image, invisible text)."""
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@hookspec(firstresult=True)
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def get_ocr_engine() -> OcrEngine:
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pass
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