Re: [ft] Accuracy of generated glyphs in smaller bitmaps

[Werner LEMBERG]

First of all, which FreeType version?

> We are having an issue with one of our TTF fonts, where the
> generated bitmaps look radically different between smaller and
> medium resolutions.

Normally, this *always* happens.  This is exactly what TrueType
instructions are designed for.

Do you use the native TrueType hinter, with bytecode handling enabled?
If the latter is disabled you might get inferior results since certain
patented instructions are replaced with workarounds.

> I attached a screenshot of some bitmaps Freetype generates from our
> Assuan TTF font at 26x26, 36x36, and 52x52 (values plugged into
> FT_Set_Pixel_Sizes).

This font looks like not being suited to small resolutions at all --
it is too fat for that purpose.  To tell anything more I need to
investigate the font itself.  In particular, the `gasp' table values
are of interest.

> The bitmaps generated at 36x36 and above are acceptable, but at
> 26x26 and below, the font looks pretty bad (Note the 'RE'
> combination in the image).

This is caused basacally by the missing serifs.  It's easily possible
that this is a badly hinted font which disables serifs below a certain
threshold without adjusting the advance width properly.

> It is very important for us to keep all font sizes below 32x32 since
> we have very limited amounts of memory to work with.

Why not using anti-aliased bitmap fonts directly?