bugThe FreeType Project - Bugs: bug #38211, Different (wrong ?) outline for TT...

 
 

bug #38211: Different (wrong ?) outline for TT font compared to Acrobat

Submitted by:  John Tytgat <joty>
Submitted on:  Thu 31 Jan 2013 04:48:15 PM UTC  
 
Severity: 3 - NormalItem Group: Incorrect behaviour
Status: FixedPrivacy: Public
Assigned to: Werner LEMBERG <wl>Open/Closed: Closed
Planned Release: 2.4.12

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Fri 01 Feb 2013 01:34:09 PM UTC, comment #1:

This is tricky. What you see actually is undefined behaviour.

The problem is the IP instruction at position 144 in the `R' glyph which should move point 25. At execution time, the reference points rp1 and rp2 are both point 27. According to the specification, this is invalid.

Up to now, FreeType did nothing in this case, this is, it ignored the invalid IP instruction. However, the TT interpreter in Acroread does move the point (and the debugger in Rogier van Dalen's `TrueTypeViewer' program moves it, too).

Consequently, I've just changed the FreeType code to do the same as TrueTypeViewer.

My conclusion is that this is a font bug, since the rendering result with the `improved' IP instruction is not really better, especially not at large PPEM values (and the font contains no `gasp' table to stop the distorting point move).

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Thu 31 Jan 2013 04:48:15 PM UTC, original submission:

Attached a PDF file and extracted Times-Bold TrueType subset font from that PDF file which shows in Acrobat that the 'R' glyph (glyph ID 53) has a different outline compared to what FreeType generates (the latter is the red stroke around the glyphs in that PDF file).

Basically I want to understand why we have that difference. Is this an Acrobat problem ? Or something which can/has to be improved in FreeType ?

John Tytgat <joty>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach File(s):
   
   
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Attached Files
file #27358:  Beispiel_mini_outlinepe_joty.pdf added by joty (121KiB - application/unknown)
file #27359:  times-bold.ttf added by joty (48KiB - application/octet-stream)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -unavailable- added by wl (Posted a comment)
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  • -unavailable- added by joty (Submitted the item)
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    Follow 7 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Fri 01 Feb 2013 10:46:58 PM UTCwlAssigned toNone=>wl
    Fri 01 Feb 2013 01:34:09 PM UTCwlStatusNone=>Fixed
      Open/ClosedOpen=>Closed
      Planned ReleaseNone=>2.4.12
      Carbon-Copy-=>Added infinality
    Thu 31 Jan 2013 04:48:15 PM UTCjotyAttached File-=>Added Beispiel_mini_outlinepe_joty.pdf, #27358
      Attached File-=>Added times-bold.ttf, #27359

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