bugThe FreeType Project - Bugs: bug #41334, Slightly wrong outline for TT glyph

 
 

bug #41334: Slightly wrong outline for TT glyph

Submitted by:  John Tytgat <joty>
Submitted on:  Fri 24 Jan 2014 04:12:26 PM UTC  
 
Severity: 3 - NormalItem Group: Incorrect behaviour
Status: ConfirmedPrivacy: Public
Assigned to: Werner LEMBERG <wl>Open/Closed: Open
Planned Release: None

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Wed 05 Feb 2014 06:39:35 PM UTC, comment #1:

Without having time currently to analyze it further, I think this is a bug in the auto-hinter algorithm of creating segments: Each line between consecutive on or off points gets a direction: up/down, left/right, or unspecified. The algorithm allows a certain deviation (approx 4°) from horizontal or vertical lines, still counting them as up/down or left/right. Such lines are collected and form a segment; normally, all points along a segment get the same coordinate.

The problematic glyph has a series of such slightly sloped lines, and all of them point into the same direction, which is very unusual. The auto-hinter then normalizes them brutally to a vertical line, not taking into account that the effect culmulates unfavorably.

A quick solution is to disable the auto-hinter by using FT_LOAD_NO_AUTOHINT – it gets used automatically for this font since it doesn't contain any bytecode instructions.

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Fri 24 Jan 2014 04:12:26 PM UTC, original submission:

Attached a subset TrueType font which has for its 'R' glyph an outline (using FT2.5.2) which is slightly different than what we see within Acrobat or Windows. I.e. FT makes its left side going a bit right way instead the other renderers make it going a bit left way.

Attached as well a screenshot which probably explains better what is meant as difference: the red filled area is what FT returns as glyph, the black stroke outline what we get with the other renderers.

Any idea what the real issue is ?

John Tytgat <joty>

 

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

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Attached Files
file #30362:  CBBWEP+CardenioModern.ttf added by joty (9kB - application/octet-stream)
file #30363:  screenshot.png added by joty (50kB - image/png)

 

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)
  • -unavailable- added by joty (Submitted the item)
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    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed 05 Feb 2014 06:39:35 PM UTCwlStatusNone=>Confirmed
      Assigned toNone=>wl
    Fri 24 Jan 2014 04:12:26 PM UTCjotyAttached File-=>Added CBBWEP+CardenioModern.ttf, #30362
      Attached File-=>Added screenshot.png, #30363

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