Would True Colour to ANSI 8-bit palette conversion be useful

Would True Colour to ANSI 8-bit palette conversion be useful

[Michał Nazarewicz]

A while back I wrote https://github.com/mina86/ansi_colours which
takes 24-bit RGB colour and spits out the best matching entry from
ANSI 8-bit palette.  I’ve recently looked through NEWS and noticed
changes related to the true colour support on the terminal.

This got me wondering whether a feature to do True Colour -> ANSI
conversion would be useful somewhere in Emacs.  The typical usage is
where the user specifies 24-bit colour but the terminal supports the
8-bit palette only.

I don’t use Emacs in terminal nor do I run terminal inside Emacs, so
honestly I’ve no idea if that would be useful.

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»

Re: Would True Colour to ANSI 8-bit palette conversion be useful

[Eli Zaretskii]

> From: Michał Nazarewicz <mina86@mina86.com>
> Date: Fri, 14 Jun 2024 06:01:19 -0400
> 
> A while back I wrote https://github.com/mina86/ansi_colours which
> takes 24-bit RGB colour and spits out the best matching entry from
> ANSI 8-bit palette.  I’ve recently looked through NEWS and noticed
> changes related to the true colour support on the terminal.
> 
> This got me wondering whether a feature to do True Colour -> ANSI
> conversion would be useful somewhere in Emacs.  The typical usage is
> where the user specifies 24-bit colour but the terminal supports the
> 8-bit palette only.

Maybe I misunderstand what you mean by that, but Emacs already
attempts to find the best color of the N colors the terminal actually
supports that approximates the color specified by a face.  That
includes the case of only 8 supported colors.  See tty-colors.el.
This transparent color approximation exists in Emacs since v21.1, and
it was necessary to let Lisp programs specify X colors without
worrying too much about what will happen on TTY frames.

If the approximation implemented in tty-color-approximate is not what
you have in mind, please tell more about your ideas.

Thanks.

Re: Would True Colour to ANSI 8-bit palette conversion be useful

[Michał Nazarewicz]

On Fri, 14 Jun 2024 at 07:14, Eli Zaretskii <eliz@gnu.org> wrote:
> Emacs already
> attempts to find the best color of the N colors the terminal actually
> supports that approximates the color specified by a face.  That
> includes the case of only 8 supported colors.  See tty-colors.el.

Yes, that’s the feature I meant. (As mentioned, I’m not using TTY so I
wasn’t aware this existed and didn’t find it with a quick look at the
codebase). I could probably argue my implementation is more
perceptually accurate but on the flip side it only works for the
256-colour palette. So it sounds like there’s nothing to see here. ;)

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»