Apply the font /Differences array to every byte of a text segment#453
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PrinsFrank
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Jul 20, 2026
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Hi, Thanks for the clear PR including a reproduction PDF!
Unfortunately I'm unable to rebase and fix commits, could you rebase and remove the comments yourself? Apart from that this is ready to merge!
The /Differences array was only consulted for single byte text segments, so multi-byte strings shown with a font whose encoding is a /Differences array without a base encoding or /ToUnicode CMap fell through to their raw bytes. Non-ASCII glyphs such as umlauts were then emitted as raw single byte codes, producing invalid UTF-8. Simple fonts are single byte encoded, so the array is now applied per byte for the whole segment, falling back to the base encoding for codes it does not remap, matching the encoding resolution in spec section 9.6.6.1.
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rebased and conflict solved. inline comment removed |
PrinsFrank
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Jul 21, 2026
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Thank you!! |
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The /Differences array was only consulted for single byte text segments, so multi-byte strings shown with a font whose encoding is a /Differences array without a base encoding or /ToUnicode CMap fell through to their raw bytes. Non-ASCII glyphs such as umlauts were then emitted as raw single byte codes, producing invalid UTF-8.
Simple fonts are single byte encoded, so the array is now applied per byte for the whole segment, falling back to the base encoding for codes it does not remap, matching the encoding resolution in spec section 9.6.6.1.
I encountered this issue when trying to convert my 20+ year old Latex-generated diploma thesis - the issue seems to be rare for modern PDFs. The commit adds a synthetic test PDF - if you need my thesis for tests, let me know ;-)