bugThe FreeType Project - Bugs: bug #20476, linearHoriAdvance is snapped to...

 
 

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bug #20476: linearHoriAdvance is snapped to some integer value with monospaced fonts

Submitter:  None
Submitted:  Fri 13 Jul 2007 03:05:52 PM UTC
   
 
Severity:  3 - Normal Item Group:  Incorrect behaviour
Status:  Wont Fix Privacy:  Public
Assigned to:  freetype Open/Closed:  Closed
Planned Release:  None

Fri 13 Jan 2017 07:29:39 AM UTC, comment #2: 

To be more precise: It was a bug that the `linearHoriAdvance' values of proportional fonts were strictly proportional to the `char_height' (or `char_width') parameter of `FT_Set_Char_Size'.

This has been fixed meanwhile (already a few years ago, I no longer remember).

The `char_height' parameter gives a size in fractional points, not pixels.  The resulting pixel size is always an integer value.

Werner LEMBERG <wl>
Group administrator
Fri 13 Jan 2017 04:16:55 AM UTC, comment #1: 

This is not a bug. The outlines are scaled and rendered properly without any rounding. The rounding of advances happens because you cannot render bitmaps at fractional pixels. Accounting for the accumulating rounding errors by adding/removing pixels won't work, because the font won't look fixed. It is what it is.

Alexei Podtelezhnikov <podtelez>
Group Member
Fri 13 Jul 2007 03:05:52 PM UTC, original submission:  

In TT font Courier New (windows file cour.ttf) linearHoriAdvance,  should be accurate and strictly proportional to the sub-pixel height you set. However, it is snapped to some value.

Font: cour.ttf from WinXP
Hinting: FT_LOAD_NO_HINTING
Then you set:
FT_Set_Char_Size(face, 0, height, 72, 72);
where "heights" are:
7.02, 7.80, 8.58, 9.36, 10.14, 10.92, 11.70, 12.48,
13.26, 14.04, 14.82, 15.60
(in the corresponding 26.6 units of course)

It results in the following picture using linearHoriAdvance:
http://antigrain.com/stuff/12cour.png
With any proportional font there's no such effect and the text width is proportional to the given height.

Anonymous

 

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Attached Files
file #13329:  12cour.png added by None (38KiB - image/png)

 

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Items that depend on this one: None found

 

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  • -email is unavailable- added by podtelez (Posted a comment)
  • -email is unavailable- added by wl (Updated the item)
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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2017-01-13 podtelez StatusNone Wont Fix
        Open/ClosedOpen Closed
    2007-07-13 wl Assigned toNone freetype
    2007-07-13 None Attached File- Added 12cour.png, #13329

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