bugThe FreeType Project - Bugs: bug #40975, TT hinting badly distorts DejaVu...

 
 

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bug #40975: TT hinting badly distorts DejaVu Sans' U+1D760 MATHEMATICAL SANS-SERIF BOLD CAPITAL LAMBDA

Submitter:  Jan Steffens <heftig>
Submitted:  Thu 19 Dec 2013 09:34:40 PM UTC
   
 
Severity:  3 - Normal Item Group:  Incorrect behaviour
Status:  Fixed Privacy:  Public
Assigned to:  wl Open/Closed:  Closed
Planned Release:  2.5.3

Jump to the original submission

Sat 21 Dec 2013 06:35:53 PM UTC, comment #7: 

Excellent, thanks!  FreeType now behaves identically to the Windows engine.

You should file a bug report to the DejaVu people so that the bad hinting gets fixed.

Werner LEMBERG <wl>
Group administrator
Sat 21 Dec 2013 06:27:36 PM UTC, comment #6: 

Ah, I forgot to mention: those are DejaVu Sans Bold U+039B and U+0394, which show the same problem as U+1D760 and U+1D759. The latter are just intrinsically bold and not in the regular typeface.

Jan Steffens <heftig>
Sat 21 Dec 2013 06:20:15 PM UTC, comment #5: 

Windows 7 isn't doing too well, either, but at least at small sizes it remains legible.


Jan Steffens <heftig>
Fri 20 Dec 2013 07:55:37 AM UTC, comment #4: 

Thanks, I can confirm the problem.

Basically, it's a bug in the instructions of glyph u1D760: The `IP' instruction is called to interpolate the position of point 1 vertically between points 0 and 2.  However, points 0 and 2 have the same vertical coordinate values (namely 0), and since the projection vector is set to (0,1), we get invalid behaviour as described in the specification.

FreeType tries to emulate Microsoft's behaviour for invalid IP instructions, and I think that I've identified a bug.  To verify this, can you provide renderings of glyph u1D760 on Windows for various resolutions?  I would like to see 12ppem and 100ppem (or something similar).

Werner LEMBERG <wl>
Group administrator
Fri 20 Dec 2013 06:43:49 AM UTC, comment #3: 

I looked a bit more closely; it's only part of the bold variant (DejaVuSans-Bold.ttf).

Jan Steffens <heftig>
Fri 20 Dec 2013 06:20:44 AM UTC, comment #2: 

I've just downloaded the latest DejaVu version; the font `DejaVuSans.ttf' (version 2.34) doesn't contain a glyph for U+1D760.  Obviously, you are using a different font...

Werner LEMBERG <wl>
Group administrator
Thu 19 Dec 2013 09:36:53 PM UTC, comment #1: 

Sorry, tried to include the glyph in the comment, but the system just cut it off at that point. Rest of comment:

Attached two renderings with and without hinting.

I don't know whether this is a font problem. Haven't tested other versions and/or platforms.

Jan Steffens <heftig>
Thu 19 Dec 2013 09:34:40 PM UTC, original submission:  

The 2.5.2 TT bytecode hinter badly distorts the following glyph from DejaVu Sans:

U+1D760 MATHEMATICAL SANS-SERIF BOLD CAPITAL LAMBDA:

Jan Steffens <heftig>

 

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

Attached Files
file #30047:  tt.png added by heftig (928B - image/png)
file #30048:  none.png added by heftig (946B - image/png)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -email is unavailable- added by wl (Posted a comment)
  • -email is unavailable- added by heftig (Submitted the item)
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    Follow 8 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2013-12-21 wl StatusNeed Info Fixed
        Open/ClosedOpen Closed
        Planned ReleaseNone 2.5.3
    2013-12-21 heftig Attached File- Added dejavu-sans-bold-windows7.png, #30055
    2013-12-20 wl StatusNone Need Info
        Assigned toNone wl
    2013-12-19 heftig Attached File- Added tt.png, #30047
        Attached File- Added none.png, #30048

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