[MPEG-OTSPEC] Documentation guidance on CFF(2) transformation

[Skef Iterum]

Let me be more specific: The VARC specification anticipates that TrueType
"instructions" will be valid and should be applied when 
compositing/rasterizing
VARC glyphs with glyf-based atoms, and that CFF2 PostScript-style hint
parameters will be valid and should be used when compositing/rasterizing
VARC glyphs with CFF2-based atoms, yielding hinted output when there is
hinted input (except in special cases such as the text itself being 
transformed
via CSS or some other means). Just extracting and transforming the path
information and then feeding it to a moveto/lineto/(q)curveto based 
rasterizer
won't support that, as such a rasterizer won't be aware of TrueType
instructions or PostScript style hinting, and anyway that data would be
stripped out of the path data.

The question is: What should the specification say to make this expectation
clear and to clarify anything else the implementer should know, at least at
a high level?

Skef

On 1/25/24 02:09, Dominik Röttsches wrote:
> Hi Skef,
>
> On Wed, Jan 24, 2024 at 11:22 PM Skef Iterum via mpeg-otspec 
> <mpeg-otspec at lists.aau.at> wrote:
>
>     I suppose the remaining question is: How do you anticipate you
>     will support VARC when it becomes part of the specification and
>     what guidance do you think the spec should provide when it comes
>     to that sort of support?
>
> I am not sure I can answer that. Similar to what I described for 
> COLRv1, I expect it to be supported below the level of retrieving a 
> path into an internal intermediate representation. So from the 
> rasterisation perspective, we rely on retrieving that path, and render 
> from there.
>
> Dominik
>
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