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A page may carry an optional /Thumb image XObject (ISO 32000-2 12.3.4), a miniature rendering used only as a navigation aid. OCRmyPDF alters page appearance (deskew, clean, rasterize, re-render) and plugins may edit pages arbitrarily, so a retained thumbnail would be stale and no longer match its page. Modern viewers generate thumbnails on demand, so there is no loss of functionality. OcrGrafter.finalize() now strips /Thumb from every page before saving, alongside the existing search-index discard, covering both the OCR and hOCR pipelines. Orphaned thumbnail XObjects are garbage-collected on save.
94 lines
2.8 KiB
Python
94 lines
2.8 KiB
Python
# SPDX-FileCopyrightText: 2024 James R. Barlow
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# SPDX-License-Identifier: MPL-2.0
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from __future__ import annotations
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import logging
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import pikepdf
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import pytest
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from pikepdf import Name
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from ocrmypdf._graft import discard_page_thumbnails
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from .conftest import check_ocrmypdf
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# pylint: disable=redefined-outer-name
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def _add_thumbnail(pdf: pikepdf.Pdf, pageindex: int = 0) -> None:
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"""Attach a minimal /Thumb image XObject to a page."""
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width, height = 4, 4
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thumb = pikepdf.Stream(pdf, b'\x00' * (width * height))
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thumb.Type = Name.XObject
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thumb.Subtype = Name.Image
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thumb.Width = width
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thumb.Height = height
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thumb.ColorSpace = Name.DeviceGray
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thumb.BitsPerComponent = 8
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pdf.pages[pageindex].obj.Thumb = pdf.make_indirect(thumb)
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def test_discard_page_thumbnails_removes_thumbnails(resources):
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with pikepdf.open(resources / 'francais.pdf') as pdf:
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# No thumbnails -> nothing to do
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assert discard_page_thumbnails(pdf) == 0
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_add_thumbnail(pdf, 0)
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assert Name.Thumb in pdf.pages[0].obj
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assert discard_page_thumbnails(pdf) == 1
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assert Name.Thumb not in pdf.pages[0].obj
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# Idempotent: a second call finds nothing to remove
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assert discard_page_thumbnails(pdf) == 0
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def test_discard_page_thumbnails_counts_each_page(resources):
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with pikepdf.open(resources / 'multipage.pdf') as pdf:
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assert len(pdf.pages) >= 2
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_add_thumbnail(pdf, 0)
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_add_thumbnail(pdf, 1)
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assert discard_page_thumbnails(pdf) == 2
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assert all(Name.Thumb not in page.obj for page in pdf.pages)
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@pytest.fixture
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def pdf_with_thumbnail(resources, outdir):
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out = outdir / 'with_thumbnail.pdf'
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with pikepdf.open(resources / 'graph.pdf') as pdf:
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_add_thumbnail(pdf, 0)
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assert Name.Thumb in pdf.pages[0].obj
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pdf.save(out)
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return out
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def test_thumbnail_discarded_end_to_end(pdf_with_thumbnail, outpdf, caplog):
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caplog.set_level(logging.DEBUG)
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check_ocrmypdf(
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pdf_with_thumbnail,
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outpdf,
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'--output-type',
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'pdf',
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'--plugin',
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'tests/plugins/tesseract_noop.py',
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)
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with pikepdf.open(outpdf) as pdf:
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assert all(Name.Thumb not in page.obj for page in pdf.pages)
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assert 'thumbnail' in caplog.text.lower()
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def test_thumbnail_discarded_with_ocr_engine_none(pdf_with_thumbnail, outpdf):
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# Even in pure image-processing mode, OCRmyPDF rewrites the PDF, which can
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# alter page appearance, so the stale thumbnail must still be discarded.
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check_ocrmypdf(
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pdf_with_thumbnail,
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outpdf,
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'--ocr-engine',
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'none',
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'--output-type',
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'pdf',
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)
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with pikepdf.open(outpdf) as pdf:
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assert all(Name.Thumb not in page.obj for page in pdf.pages)
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