cterm256

ANSI 8/16 => 256 color table generator & collection of 256-table'based configurations for CLI/TUI apps.

Goals of this project

• Use the same color coding for CLI/TUI apps
• Ability to quickly change the color scheme, including for already running applications
• Generate 256 colors table based on 8/16 colors of any custom theme

Use the same color coding for CLI/TUI apps

I think it’s nice to see semantically colored text in one color coding space across diffirent terminal apps output.

Ability to quickly change the color scheme, including for already running applications

If applications will use indexed color table, you can just change colors in that table. All that apps will change thier colorschemes with that one action. It is especially usefull when you're need to switch from dark to light theme and vice-versa.

Generate 256 colors table based on 8/16 colors of any custom theme

Most (if not all) of color schemes for terminals defines only 8 or 16 colors. With that assumption we can try to generate another colors in table based on that 8/16.

Installation

Color table generator is an Go CLI app. Which can be installed like this:

go install -v github.com/shagohead/cterm256/cmd/cterm256@latest

Currently generator supports only kitty color themes, but it can be extended by implementation of cterm.FileType interface and adding that implementation into internal/filetypes/filetypes.go flag values.

Configurations which are uses generated color scheme located are in ./configs directory.

Reason of this project

Years ago i was used base16 terminal themes. But for me, 16 is not enough, i need variations of these 16 base colors. Mainly due to the need for different backgrounds: added/removed/changed blocks of code in diffs and UI elements of TUI apps like Vim/Neovim, Tig and so on.

I decided to use 8-bit ANSI color table. Most of color schemes at internet defines only standard & high intensity colors which stands at 0-7 and 8-15 numbers in that table. Another 240 colors are: 6x6x6 cube and 24-length grayscale. How to generate these colorspace from theme defined 8/16 colors?

Algorithm

Grayscale can be maded by generating gradient of lightness based on black color (which number is 0). For 6x6x6 cube i've found these correlations:

• Top-left color of first side is the black (#0) color.
• Top row (5 colors, except top-left black) of first side is the gradient of blue (#12).
• Left column (5 colors, except top-left black) of first side is the gradient red (#9).
• Top-left color of all 5 remaining sides is the gradient of green (#10).
• Top row of remaining sides is the gradient made by mixing of top-left green and blue from the top row of the first side.
• Left column of remaining sides is the gradient made by mixing of top-left green and red from the left column of the first side.
• All remain colors made by mixing intersecting top row and left column and top-left cell colors.

Because some of these colors will be used as backgrounds, they need to have same lightness as the background. With that, cube generated from standard colors will be slightly diffirent to standard cube.

Lightness variations generated in HSLuv (developer oriented CIELUV) colors space, which produces accurate results, which especially important for backgrounds.

TODO

Try github.com/lucasb-eyer/go-colorful, which can prevent creating wrong colors for RGB: https://github.com/lucasb-eyer/go-colorful?tab=readme-ov-file#q-labluvhcl-seem-broken-your-library-sucks

Autofix black & white colors for light-background themes by reversing them.

Add images & video previews as examples of how it works and feels.