Make --output-type auto fall back to Ghostscript for PDF/A
This commit is contained in:
James R. Barlow
+53
-17
@@ -32,12 +32,14 @@ from ocrmypdf._options import OcrOptions, ProcessingMode, TaggedPdfMode
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from ocrmypdf._pageboxes import log_box_repairs, repair_page_boxes
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from ocrmypdf._stdoutprotect import get_protected_stdout_fd
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from ocrmypdf.exceptions import (
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ColorConversionNeededError,
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DigitalSignatureError,
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DpiError,
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EncryptedPdfError,
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InputFileError,
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NonEmbeddedFontsError,
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PriorOcrFoundError,
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SubprocessOutputError,
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TaggedPDFError,
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UnsupportedImageFormatError,
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)
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@@ -1078,14 +1080,46 @@ def try_speculative_pdfa(input_pdf: Path, context: PdfContext) -> Path | None:
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return None
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def _ghostscript_pdfa_fallback(input_pdf: Path, context: PdfContext) -> Path | None:
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"""Best-effort PDF/A conversion via Ghostscript for 'auto' output type.
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Returns the converted PDF/A path, or None if Ghostscript is unavailable,
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fails, or cannot produce valid PDF/A. Never raises: 'auto' mode degrades to
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a regular PDF instead of erroring or emitting corrupted output.
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Args:
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input_pdf: Path to the PDF to convert.
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context: The PDF context.
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"""
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from ocrmypdf._exec import ghostscript
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if not ghostscript.available():
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return None
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try:
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ps_stub = generate_postscript_stub(context)
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gs_out = convert_to_pdfa(input_pdf, ps_stub, context)
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except (
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SubprocessOutputError,
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ColorConversionNeededError,
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NonEmbeddedFontsError,
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) as e:
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log.info('Auto mode: Ghostscript could not produce PDF/A (%s)', e)
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return None
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if not file_claims_pdfa(gs_out)['pass']:
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log.info('Auto mode: Ghostscript output is not valid PDF/A')
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return None
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return gs_out
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def try_auto_pdfa(input_pdf: Path, context: PdfContext) -> tuple[Path, str]:
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"""Best-effort PDF/A for 'auto' output type.
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This function attempts to produce PDF/A without requiring Ghostscript:
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1. If verapdf is available, tries speculative conversion with validation
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2. Without verapdf, passes through as PDF/A if safe (input already PDF/A
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or force-ocr was used)
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3. Falls back to regular PDF if neither condition is met
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Order of attempts, first success wins:
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1. Non-embedded CID fonts -> regular PDF (Ghostscript would corrupt them).
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2. Speculative conversion validated by verapdf (no Ghostscript).
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3. Without verapdf, pass through if already PDF/A or rebuilt with force-ocr.
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4. Ghostscript conversion (best-effort; failures fall through).
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5. Regular PDF if none of the above produced PDF/A.
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Args:
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input_pdf: Path to the PDF to convert
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@@ -1112,25 +1146,27 @@ def try_auto_pdfa(input_pdf: Path, context: PdfContext) -> tuple[Path, str]:
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)
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return (input_pdf, 'pdf')
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# If verapdf available, try speculative conversion with validation
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# Cheap path: speculative conversion validated by verapdf (no Ghostscript).
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if verapdf.available():
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result = try_speculative_pdfa(input_pdf, context)
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if result is not None:
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return (result, 'pdfa')
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# verapdf validation failed - fall through to regular PDF
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log.info(
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'Auto mode: speculative PDF/A validation failed, outputting regular PDF'
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)
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return (input_pdf, 'pdf')
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# Without verapdf, check if we can pass through as PDF/A
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if _is_safe_pdfa(input_pdf, context.options):
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# Pass through as-is (no modifications needed)
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log.info('Auto mode: speculative PDF/A validation failed')
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elif _is_safe_pdfa(input_pdf, context.options):
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# No verapdf, but the input is already PDF/A or was rebuilt with
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# --force-ocr, so we can pass it through without Ghostscript.
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log.info('Auto mode: passing through as PDF/A (input already compliant)')
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return (input_pdf, 'pdfa')
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# Fall through to regular PDF
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log.info('Auto mode: no verapdf available and input is not PDF/A, outputting PDF')
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# Fall back to Ghostscript to produce real PDF/A (v16 behavior). Best-effort:
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# if Ghostscript is unavailable or cannot safely produce PDF/A, keep a
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# regular PDF rather than error.
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gs_out = _ghostscript_pdfa_fallback(input_pdf, context)
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if gs_out is not None:
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log.info('Auto mode: produced PDF/A via Ghostscript')
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return (gs_out, 'pdfa')
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log.info('Auto mode: could not produce PDF/A, outputting regular PDF')
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return (input_pdf, 'pdf')
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@@ -150,6 +150,78 @@ def test_auto_downgrades_nonembedded_cid_font_to_pdf(nonembedded_cid_pdf, outpdf
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assert find_nonembedded_cid_fonts(pdf)
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def test_auto_falls_back_to_ghostscript_for_pdfa(resources, outpdf, monkeypatch):
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"""Auto mode produces PDF/A via Ghostscript when the cheap path can't."""
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# Force the speculative (veraPDF) path off so the fallback is exercised.
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monkeypatch.setattr('ocrmypdf._exec.verapdf.available', lambda: False)
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check_ocrmypdf(
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resources / 'francais.pdf',
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outpdf,
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'--plugin',
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'tests/plugins/tesseract_noop.py',
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'--output-type',
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'auto',
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)
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assert file_claims_pdfa(outpdf)['pass']
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def test_auto_outputs_pdf_when_ghostscript_unavailable(resources, outpdf, monkeypatch):
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"""With neither veraPDF nor Ghostscript, auto outputs a plain PDF."""
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monkeypatch.setattr('ocrmypdf._exec.verapdf.available', lambda: False)
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monkeypatch.setattr('ocrmypdf._exec.ghostscript.available', lambda: False)
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check_ocrmypdf(
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resources / 'francais.pdf',
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outpdf,
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'--plugin',
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'tests/plugins/tesseract_noop.py',
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'--output-type',
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'auto',
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)
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assert not file_claims_pdfa(outpdf)['pass']
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def test_auto_degrades_when_ghostscript_cannot_make_pdfa(
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resources, outpdf, monkeypatch
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):
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"""If Ghostscript produces non-PDF/A output, auto keeps a plain PDF (no error)."""
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monkeypatch.setattr('ocrmypdf._exec.verapdf.available', lambda: False)
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exitcode = run_ocrmypdf_api(
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resources / 'francais.pdf',
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outpdf,
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'--plugin',
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'tests/plugins/tesseract_noop.py',
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'--plugin',
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'tests/plugins/gs_pdfa_failure.py',
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'--output-type',
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'auto',
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)
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assert exitcode == ExitCode.ok
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assert outpdf.exists()
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assert not file_claims_pdfa(outpdf)['pass']
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def test_auto_degrades_when_ghostscript_raises(resources, outpdf, monkeypatch):
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"""A Ghostscript conversion exception in auto mode degrades to plain PDF."""
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from ocrmypdf.exceptions import ColorConversionNeededError
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monkeypatch.setattr('ocrmypdf._exec.verapdf.available', lambda: False)
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def boom(*args, **kwargs):
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raise ColorConversionNeededError()
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monkeypatch.setattr('ocrmypdf._pipeline.convert_to_pdfa', boom)
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exitcode = run_ocrmypdf_api(
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resources / 'francais.pdf',
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outpdf,
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'--plugin',
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'tests/plugins/tesseract_noop.py',
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'--output-type',
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'auto',
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)
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assert exitcode == ExitCode.ok
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assert not file_claims_pdfa(outpdf)['pass']
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@pytest.mark.parametrize('optimize', (0, 3))
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@pytest.mark.parametrize('pdfa_level', (1, 2, 3))
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def test_pdfa(resources, outpdf, optimize, pdfa_level):
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