The test asserted that --mode skip preserves the structure tree, but with
the default --output-type auto the output runs through Ghostscript PDF/A
conversion, which discards /StructTreeRoot on Ghostscript 10.x (9.x kept
it). This failed on macOS CI and locally while passing on the Ubuntu
runners' Ghostscript 9.55. Pin the test to --output-type pdf so it exercises
OCRmyPDF's own structure-tree handling without the version-dependent GS step,
and document the caveat in advanced.md.
A tagged/structured PDF carries a logical structure tree
(/Root/StructTreeRoot, /MarkInfo) that maps marked page content to
semantic elements via MCIDs. When --force-ocr rasterizes pages or
--redo-ocr rewrites the text layer, those MCIDs are destroyed or
renumbered and the tree is left dangling. We cannot rebuild it to match
the new text, so discard it for force/redo modes, following the same
pattern as the thumbnail and search-index discards. --skip-text leaves
text pages untouched, so their structure is preserved.
Also broaden the default-mode "looks born-digital" stop signal to fire
on /StructTreeRoot, not just /MarkInfo/Marked, so structure-tree-only
PDFs are no longer silently OCR'd. The existing --tagged-pdf-mode ignore
escape hatch is unchanged.
Allow users to bypass the TaggedPDFError when processing Tagged PDFs
by setting --tagged-pdf-mode=ignore. This is useful when users know
they want to OCR a Tagged PDF despite the warning.
- 'default': Error if --mode is default, otherwise warn (current behavior)
- 'ignore': Always warn but continue processing (never error)
James R. Barlow