A quick python script I wrote to transform the base16 colors of the onedark theme

transform.py

#!/usr/bin/env python3

import yaml
import colorsys

def hex2rgb(hex: str) -> tuple[int]:
    return tuple(int(hex[i:i+2], 16) for i in (0, 2, 4))

def rgb2hex(rgb: tuple[int]):
    return "%x%x%x" % rgb

if __name__ == "__main__":
    with open("onedark.yaml", "r") as f:
        theme = yaml.safe_load(f)

        for k, v1 in theme["palette"].items():
            old = colorsys.rgb_to_hls(*hex2rgb(v1.lstrip('#')))
            new = colorsys.hls_to_rgb(old[0], old[1] - 10, old[2])

            theme["palette"][k] = '#' + rgb2hex(tuple([round(x) for x in new]))

        with open("base16.yaml", "w") as f:
            yaml.dump(theme, f)

# 282c34  ===>  1f2329
# abb2bf  ===>  a0a8b7
"""
    bg1, bg2 = hex2rgb("282c34"), hex2rgb("1f2329")
    fg1, fg2 = hex2rgb("abb2bf"), hex2rgb("a0a8b7")

    bg1_hls, bg2_hls = colorsys.rgb_to_hls(*bg1), colorsys.rgb_to_hls(*bg2)
    fg1_hls, fg2_hls = colorsys.rgb_to_hls(*fg1), colorsys.rgb_to_hls(*fg2)

    print(bg1_hls); print(bg2_hls); print("\n")
    print(fg1_hls); print(fg2_hls); print("\n")
"""

Original theme came from: https://github.com/tinted-theming/schemes/blob/spec-0.11/base16/onedark.yaml
The colors that I wanted came from: https://github.com/navarasu/onedark.nvim/blob/master/lua/onedark/palette.lua

Using Python, I converted the colors from Hex to RGB, then RGB to HLS. I saw a pattern in how the colors transformed between the two themes, and replicated that transformation across all colors.

It's good to note that this isn't a 100% accurate conversion. Small rounding flaws, slight color variants in the magnitude of 0.5–4 in any/all RGB values were present when testing with a small handful of sample values from the two themes. The difference is extremely negligible, so it was ignored.

I actually think it might be a really cool exercise to right a machine learning program to find the transformation as well. Not a project that I'm interested in right now though.