RE: [ft-devel] ft-smooth for 2.1.10?

[Turner, David]

Ah, I'll try to explain, there is something ambiguous there,
and we need to make the documentation clearer about this.

I'll try to sum it up as:

A/ the FT_LOAD_TARGET_XXX values are used with FT_Load_Glyph
   and specify a *hinting* algorithm to the outline loader.

B/ the FT_RENDER_MODE_XXX values are used with FT_Render_Glyph
   and specify a *rendering* algorithm, which can be either
   monochrome, gray, LCD or LCD_V.

the confusion comes from the existence of FT_RENDER_MODE_LIGHT,
because:

  - when it is used in FT_Render_Glyph, or other rendering
    function, it is equivalent to FT_RENDER_MODE_NORMAL,
    which correspond to gray rendering.

  - the value is also used to build FT_LOAD_TARGET_LIGHT,
    which however instructs the auto-hinter called by
    FT_Load_Glyph to perform a "light" outline distorsion.

suppose that you want to perform LIGHT hinting, but render
to a LCD surface, you'd do something like:

   FT_Load_Glyph( face, glyph_index, FT_LOAD_TARGET_LIGHT );
   FT_Render_Glyph( face, FT_RENDER_MODE_LCD );

now, there is the FT_LOAD_RENDER bit-flag, that instructs
FT_Load_Glyph to perform rendering just after the outline
was hinted. When you call:

   FT_Load_Glyph( face, gindex, FT_LOAD_TARGET_XXX | FT_LOAD_RENDER );

this is equivalent to:

  FT_Load_Glyph( face, gindex, FT_LOARD_TARGET_XXX );
  FT_Render_Glyph( face, FT_RENDER_MODE_XXX );

so, when XXX is LIGHT, you get LIGHT hinting, and gray rendering
by default with this bit-flag set.

The problem comes from the fact that the same values are used to
specify hinting algorithms and rendering modes.

The documentation probably needs some update.

Hope this helps,

- David



> -----Message d'origine-----
> De : address@hidden [mailto:address@hidden
> Envoyé : mardi 20 décembre 2005 12:31
> À : Turner, David; David Turner; address@hidden
> Objet : RE: [ft-devel] ft-smooth for 2.1.10?
>
>
> Hello David,
>
> > > what exactly
> > > is the API change, and since when?
> > >
> > > FT_LOAD_TARGET_LIGHT and FT_RENDER_MODE_LIGHT did nothing for
> > > in 2.1.10.
> > >
> >
> > There is no API change, it's simply the algorithm used to implement
> > the LIGHT hinting mode that has been modified.
> >
> > Moreover, in 2.1.10, this mode did actually perform something.
>
> From the API docs I read this:
>
> FT_LOAD_TARGET_LIGHT:
> Use hinting for FT_RENDER_MODE_LIGHT.
>
> FT_RENDER_MODE_LIGHT:
> This is similar to FT_RENDER_MODE_NORMAL -- you have to use
> FT_LOAD_TARGET_LIGHT in calls to FT_Load_Glyph to get any effect since
> the rendering process no longer influences the positioning of glyph
> outlines. The resulting glyph shapes are more similar to the original,
> while being a bit more fuzzy (`better shapes' instead of `better
> contrast', so to say.
>
> ---
>
> What I make up of this: FT_RENDER_MODE_LIGHT has become
> deprecated, and
> specifying it is exactly the same as specifying FT_RENDER_MODE_NORMAL.
>
> I should only use FT_LOAD_TARGET_LIGHT in FT_Load_Glyph().
>
> So:
>
> error = FT_Load_Char( face, text[n], FT_LOAD_DEFAULT |
> FT_LOAD_TARGET_LIGHT)
> ...
> error = FT_Glyph_To_Bitmap( &glyph, FT_RENDER_MODE_NORMAL, 0, 1 );
>
> ---
>
>
> If my assumption is correct, I would suggest moving the explanation to
> the FT_LOAD_TARGET_LIGHT flag docs, and have
> FT_RENDER_MODE_LIGHT refer
> to FT_LOAD_TARGET_LIGHT.
>
> Furthermore, on the web API docs, I noticed
> FT_LOAD_TARGET_LIGHT is not
> in the FT_LOAD_XXX list that sits before their descriptions.
>
>
> Thanks, best regards,
>
> Leon.
>
>
>
> On Tue, 20 Dec 2005 10:15:11 +0100, "Turner, David" <address@hidden>
> said:
> > Hi Leon,
> >
> > > For those of us using and/or testing FreeType standalone,
> > > what exactly
> > > is the API change, and since when?
> > >
> > > FT_LOAD_TARGET_LIGHT and FT_RENDER_MODE_LIGHT did nothing for
> > > in 2.1.10.
> > >
> >
> > There is no API change, it's simply the algorithm used to implement
> > the LIGHT hinting mode that has been modified.
> >
> > Moreover, in 2.1.10, this mode did actually perform something.
> > This can be demo-ed with "ftview" and the "L" key to cycle between
> > target modes.
> >
> > Regards,
> >
> > - David
> >
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