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https://issues.apache.org/jira/browse/PDFBOX-3293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18093865#comment-18093865
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Patrick Corless commented on PDFBOX-3293:
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Hi all,
I've been working in this space for a while (ICEpdf, which uses FontBox), and I
recently took a run at the overlapping-path problem described here. I
implemented a hinting/rasterization approach for the FontBox glyph pipeline
aimed squarely at the small-size CJK rendering artifacts this ticket describes.
The early results are very promising:
- No special-case exclusion rules — it's a general approach, not a per-font
workaround.
- Works across all the fonts I've tested, including the Traditional Chinese
fonts called out here (MingLiU, PMingLiU, DFKai-SB).
- Fast — no meaningful rendering-performance penalty.
Full disclosure on method: I built this by combining my prior experience in
this area with some agentic/AI-assisted development to move quickly. Happy to
say more about that if it's useful.
My question for the maintainers: would this be something worth contributing
back formally to FontBox/PDFBox? I'd be glad to put together a proper patch or
PR, share test PDFs and before/after comparisons, and work with you on getting
it into shape. Just wanted to gauge interest before investing in the
contribution process.
Thanks!
> Chinese font glyphs with overlapping paths not rendered correctly
> -----------------------------------------------------------------
>
> Key: PDFBOX-3293
> URL: https://issues.apache.org/jira/browse/PDFBOX-3293
> Project: PDFBox
> Issue Type: Bug
> Components: FontBox, Rendering
> Affects Versions: 2.0.0
> Reporter: Pei-Tang Huang
> Priority: Major
> Attachments: PDFBOX-3293.ttf, PDFBOX-3293_reduced.pdf, fontforge.png,
> glyf.png, hinted.png, sample.pdf, sample_rendered.tif, unhinted.png
>
>
> Font glyphs with overlapping paths may be rendered in correctly, especially
> when the font size is small.
> Sadly, the Traditional Chinese edition of Windows bundled fonts 細明體&新細明體
> (MingLiU & PMingLiU) and 標楷體 (DFKai-SB) all suffer from this problem.
> See attached sample.pdf and the rendered sample_rendered.tif.
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