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https://issues.apache.org/jira/browse/PDFBOX-6288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18144822#comment-18144822
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Andreas Lehmkühler edited comment on PDFBOX-6288 at 11/14/26, 1:45 PM:
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The idea is quite simple, who ever came up with it ;)
If the font is missing and the encoding isn't Identity, try to convert the code
to a readable character using the ToUnicode mapping, similar to text
extraction. Use a fallback font which hopefully supports all characters we are
looking for. Without that we had to rely on a font which uses the very same
encoding than the missing one and that's more or less likely.
was (Author: lehmi):
The idea is quite simple, who ever came up with it ;)
If the font is missing and the encoding isn't Identity, try to convert the code
to a readable character using the ToUnicode mapping, similar to text
extraction. Use a font which hopefully supports all characters we are looking
for. Without that we had to rely on a font which uses the very same encoding
than the missing one and that's more or less likely.
> Invalid ToUnicode CMap
> ----------------------
>
> Key: PDFBOX-6288
> URL: https://issues.apache.org/jira/browse/PDFBOX-6288
> Project: PDFBox
> Issue Type: Bug
> Reporter: Oliver Schmidtmer
> Priority: Major
> Attachments: MalformedToUnicodeCMap.pdf,
> image-2026-11-12-12-51-25-119.png, image-2026-11-12-12-53-07-456.png,
> image-2026-11-12-12-55-54-029.png, toUnicode-CMAP.patch
>
>
> A problematic PDF file contains a "ToUnicode CMap" that uses "begincidrange"
> instead of "beginbfchar" or "beginbfrange".
> Since the CMap is ignored in this case, the wrong glyphs are used during
> rendering. Because the file displays correctly in Acrobat, a workaround might
> be justified.
> The attached PDF file is a generated example, as the original contains
> sensitive data. I used Copilot for the analysis and to create a potential
> patch:
> https://github.com/Schmidor/pdfbox/commit/425e83caaa28c66e6e4438c7818f0eb0a448fae9
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