Re: [ft-devel] CPAL interface

[Alexei Podtelezhnikov]

On Fri, May 18, 2018 at 1:18 AM, Werner LEMBERG <address@hidden> wrote:
>
>>> Not for this case, as far as I can see.  The code to blend two
>>> color layers as specified in COLR/CPAL is (currently) function
>>> `tt_face_colr_blend_layer'.
>>
>> I strongly suggest that this is removed.  Linear blending is bad
>> anyway.  We should just provide coverage maps for each layer
>> (including MONO and LCD optimized ones) and let client libraries
>> with good gamma-corrected blending do the final assembly job.  We
>> stayed away from blending and should continue to do so.
>
> Mhmm, I disagree.  I think that FreeType should provide a single, most
> basic solution for convenience – it's really just a few lines of code.
> This is also a wish from
>
>   https://savannah.nongnu.org/bugs/?44689#comment22
>
> I'm no expert in blending, so please help improve the code!  It should
> do the right thing in a clean way, not necessarily as fast as
> possible.

Lets do it properly then. Let's blend a layer or a glyph (in color)
onto an arbitrary background image with gamma correction. I just
checked that finite difference approximation for gamma ramps works
pretty good.