RGB SGR sequences support (truecolor)

[XVilka]

See https://gist.github.com/XVilka/8346728

• 24bit true colour ("888" colours (aka 16 milion))

printf "\x1b[${bg};2;${red};${green};${blue}m\n"

The 256 colour palete is configured at start, and it's a 666 cube of
colours, each of them defined as a 24bit (888 rgb) colour.

This means that current support can only display 256 different colours
in the terminal, while truecolour means that you can display 16 milion
different colours at the same time.

Truecolour escape codes doesnt uses a colour palete. It just specifies the
colour itself.

Here's a test case:

printf "\x1b[38;2;255;100;0mTRUECOLOR\x1b[0m\n"

• or https://raw.githubusercontent.com/JohnMorales/dotfiles/master/colors/24-bit-color.sh
• or http://github.com/robertknight/konsole/tree/master/tests/color-spaces.pl
• or https://git.gnome.org/browse/vte/tree/perf/img.sh?h=vte-0-36
• or just run this:

awk 'BEGIN{
    s="/\\/\\/\\/\\/\\"; s=s s s s s s s s;
    for (colnum = 0; colnum<77; colnum++) {
        r = 255-(colnum*255/76);
        g = (colnum*510/76);
        b = (colnum*255/76);
        if (g>255) g = 510-g;
        printf "\033[48;2;%d;%d;%dm", r,g,b;
        printf "\033[38;2;%d;%d;%dm", 255-r,255-g,255-b;
        printf "%s\033[0m", substr(s,colnum+1,1);
    }
    printf "\n";
}'

Keep in mind that it is possible to use both ';' and ':' as parameters delimiter.

According to Wikipedia[1], this is only supported by xterm and konsole.

[1] https://en.wikipedia.org/wiki/ANSI_color

Currently, there is no support for the 24-bit colour descriptions in the terminfo/termcap database and utilites.
See the discussion thread here: https://lists.gnu.org/archive/html/bug-ncurses/2013-10/msg00007.html

Here are terminals discussions:

Now supporting truecolour

• st (from suckless) [delimeter: semicolon] - http://lists.suckless.org/dev/1307/16688.html
• konsole [delimeter: colon, semicolon] - https://bugs.kde.org/show_bug.cgi?id=107487
• iterm2 [delimeter: colon, semicolon] - since v3 version
• qterminal [delimeter: semicolon] - Colons support in RGB definition lxqt/qterminal#78
• alacritty [delimeter: semicolon] - written in Rust.
• cool-retro-term [delimeter: semicolon]
• Black Screen [delimeter: semicolon] - crossplatform, HTML/CSS/JS-based
• Hyper.app [delimeter: semicolon] - crossplatform, HTML/CSS/JS-based (Electron)
• Tera Term [delimeter: colon, semicolon] - Windows platform
• ConEmu [delimeter: semicolon] - Windows platform
• FinalTerm [delimeter: semicolon] - abandoned, iTerm2 borrowing it's ideas and features.
• MacTerm [delimeter: semicolon] - Mac OS X platform
• mintty [delimeter: semicolon] Cygwin and MSYS/MSYS2 since commit mintty/mintty@43f0ed8 (2.0.1 release) - Windows platform
• Windows 10 bash console, since Windows Insiders build 14931
• all libvte based terminals (since 0.36 version) [delimeter: colon, semilocon] - https://bugzilla.gnome.org/show_bug.cgi?id=704449
  • libvte-based Gnome Terminal
  • libvte-based sakura
  • libvte-based xfce4-terminal - since 0.6.90 release, if compiled with GTK+3
  • libvte-based Terminator - since 1.90 release, if compiled with GTK+3
  • libvte-based Terminix - written in D. Similar user interface as for Terminator.
  • libvte-based Lilyterm - since commit Tetralet/LilyTerm@72536e7
  • libvte-based ROXTerm
  • libvte-based evilvte - no release yet, version from git https://github.com/caleb-/evilvte
  • libvte-based Termit
  • libvte-based Termite
  • libvte-based Tilda
  • libvte-based tinyterm
  • libvte-based Pantheon Terminal
  • libvte-based lxterminal - with --enable-gtk3 configure flag.
  • libvte-based mlterm - with --with-gtk=3.0 configure flag

But there are bunch of libvte-based terminals for GTK2 so they are listed in the another section.

Also, while this one is not exactly a terminal, but a terminal replayer, it still worth mentioning:

• asciinema player: https://github.com/asciinema/asciinema-player

Parsing ANSI colour sequences, but approximating them to 256 palette

• xterm (though doing it wrong: "it uses nearest colour in RGB colour space, with a usualfalse assumption about orthogonal axes")
• urxvt aka rxvt-unicode - since Revision 1.570 http://lists.schmorp.de/pipermail/rxvt-unicode/2016q2/002261.html
• linux console (since v3.16): torvalds/linux@cec5b2a

Note about colour differences: a) RGB axes are not orthogonal, so you cannot use sqrt(R^2+G^2+B^2) formula, b) for colour differences there is more correct (but much more complex) CIEDE2000 formula (which may easily blow up performance if used blindly) [2].

[2] neovim/neovim#793 (comment)

Terminal multiplexers

• tmux - starting from version 2.2 (support since 427b820...)
• screen - has support in 'master' branch, need to be enabled (see 'truecolor' option)
• pymux - tmux clone in pure Python (to enable truecolour run pymux with --truecolor option)
• dvtm - not yet supporting True Colour Add support for true color martanne/dvtm#10

NOT supporting truecolour

• Terminology (Enlightenment) - https://phab.enlightenment.org/T746
• mrxvt (looks abandoned) - https://sourceforge.net/p/materm/feature-requests/41/
• aterm (looks abandoned) - https://sourceforge.net/p/aterm/feature-requests/23/
• fbcon (from linux kernel) - https://bugzilla.kernel.org/show_bug.cgi?id=79551
• FreeBSD console - https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191652
• yaft framebuffer terminal - RGB SGR sequences support (truecolor) uobikiemukot/yaft#12
• PuTTY (patched version [3] {xterm-like approximation to 256 colors} and [4] {real true colors} available) - Windows platform
• libvte and GTK2 - based:
  • libvte-based GTKTerm2
  • libvte-based stjerm (looks abandoned) - GTK3 and lbvte >= 0.3x support stjerm/stjerm#39

[3] You can download patched version here https://github.com/rdebath/PuTTY

[4] You can download patched version here https://github.com/halcy/PuTTY

Here are another console programs discussions:

Supporting True Colour:

• mc - since 682a5.... See also ticket #3742 for truecolor themes.
• irssi - since PR #48
• neovim - since commit 8dd415e887923f99ab5daaeba9f0303e173dd1aa; need to set termguicolors to enable true color.
• vim - (from 7.4.1770) since commit 8a633e3427b47286869aa4b96f2bfc1fe65b25cd; need to set termguicolors to enable true color.
• elinks - configure.in:1410 (./configure --enable-true-color)
• s-lang library - (since pre2.3.1-35, for 64bit systems)
• timg - Terminal Image Viewer
• tv - tool to quickly view high-resolution multi-band imagery directly in terminal
• mpv - video player with support of console-only output (since mpv-player/mpv@dd02369)
• radare2 - reverse engineering franework; since be46b9... commit.

Not supporting True Colour:

• mutt - http://dev.mutt.org/trac/ticket/3674
• neomutt - Neomutt true colors support neomutt/neomutt#85
• ncurses library - https://lists.gnu.org/archive/html/bug-ncurses/2013-10/msg00007.html
• termbox library - 24 bit colors support (true colors) nsf/termbox#37
• mcabber - https://bitbucket.org/McKael/mcabber-crew/issue/126/support-for-true-color-16-millions-colors
• emacs - http://emacs.1067599.n5.nabble.com/RFC-Add-tty-True-Color-support-td299962.html and http://emacs.1067599.n5.nabble.com/bug-20243-True-color-terminal-support-tc354040.html
• tig - Support for True Color (16 millions colors) jonas/tig#227

[kovidgoyal]

kitty already supports truecolor. See the screenshot on the readme for an example, which shows vim witha truecolor theme. Indeed, kitty even supprots setting truecolor based colors for the underline, by extending the SGR codes.

[XVilka]

Thanks! Added in the gist.