Re: [PATCH] New function: color-blend

[Joseph Turner]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Joseph Turner <joseph@breatheoutbreathe.in>
>> Date: Fri, 01 Nov 2024 22:29:41 -0700
>> 
>> Here's `color-blend', a function to blend two colors into one.  The
>> patchset also replaces `vtable--color-blend' with `color-blend'.
>> 
>> Examples of this function being implemented separately in the wild:
>> 
>> https://github.com/alphapapa/prism.el/blob/2fa8eb5a9ca62a548d33befef4517e5d0266eb28/prism.el#L1044
>> https://oremacs.com/2015/04/28/blending-faces/
>
> Thanks.
>
>> +---
>> +** New function 'color-blend'.
>> +This function blends two RGB lists into one.
>
> This should explain what the function does, in terms that are clear
> even to those who are not experts in this area.  AFAIU, "color
> blending" has at least two different meanings.
>
>> +(defun color-blend (a b &optional alpha)
>> +  "Blend the two colors A and B with ALPHA.
>> +A and B should be lists (RED GREEN BLUE), where each element is
>> +between 0.0 and 1.0, inclusive.  ALPHA controls the influence A
>> +has on the result and should be between 0.0 and 1.0, inclusive."
>
> The doc string should document the return value.  Perhaps an example
> of blending will also be a good addition to the doc string.

> From: Yuri Khan <yuri.v.khan@gmail.com>
> Subject: Re: [PATCH] New function: color-blend
> To: Joseph Turner <joseph@breatheoutbreathe.in>
> Cc: Emacs Devel Mailing List <emacs-devel@gnu.org>
> Date: Sat, 2 Nov 2024 18:26:57 +0700 (6 hours, 32 minutes, 20 seconds ago)
> Flags: seen, personal
> Maildir: /joseph-breatheoutbreathein/INBOX

> On Sat, 2 Nov 2024 at 14:03, Joseph Turner <joseph@breatheoutbreathe.in> 
> wrote:

> > Here's `color-blend', a function to blend two colors into one.

> It would be nice to explicitly mention linear RGB space. Most
> users[citation needed] these days are accustomed to colors specified
> in sRGB space and naïve conversion dividing by 255 will not give the
> desired blends. As an example, linear mixing black (0 0 0) with white
> (1 1 1) yields (0.5 0.5 0.5). Naïve scaling will yield #808080 whereas
> middle gray is somewhere around #bebebe in sRGB.

Thanks for the feedback!  Please see the attached revised patch.

0001-Add-color-blend-to-blend-two-RGB-lists.patch
Description: Text Data

0002-Replace-vtable-color-blend-with-color-blend.patch
Description: Text Data