convert colors from dark mode to light mode

a_dark2light.py

import re
import sys
import colorsys


def clamp(x, _min, _max):
    return max(_min, min(x, _max))


def hsl_clamp_l(hex: str, _min: float, _max: float):
    assert hex.startswith("#") and (len(hex) == 7)
    r, g, b = int(hex[1:3], 16), int(hex[3:5], 16), int(hex[5:7], 16)
    h, l, s = colorsys.rgb_to_hls(r / 255, g / 255, b / 255)
    l = clamp(l, _min, _max)
    r_new, g_new, b_new = [int(x * 255) for x in colorsys.hls_to_rgb(h, l, s)]
    return f"#{r_new:2x}{g_new:2x}{b_new:2x}"


COLOR_RE = re.compile(r"([a-z]*-?color:#[0-9a-fA-F]{6})")
for chunk in re.split(COLOR_RE, sys.stdin.read()):
    if re.match(COLOR_RE, chunk) and chunk.startswith("color:"):
        hex = chunk[len("color:") :]
        new_hex = hsl_clamp_l(hex, 0, 0.4)  # foreground color should be dark
        print(f"color:{new_hex}", end="")
    elif re.match(COLOR_RE, chunk) and chunk.startswith("background-color:"):
        hex = chunk[len("background-color:") :]
        new_hex = hsl_clamp_l(hex, 0.6, 1)  # background color should be light
        print(f"background-color:{new_hex}", end="")
    else:
        print(chunk, end="")

b_explanation.md

I convert all colors to HLS, and then ensure that all foreground colors are between 0% and 40% light, and all background colors are between 60% and 100% light.

This works specifically with the output of ANSI HTML adapter (aha), which I assume to be similar to ansi2html. Looping over re.split is just a nice way to make a traditional unixy pipeline tool.

Here are some examples of syntax highlighted git diffs with two different syntax themes:

	Visual Studio Dark+	Solarized
original
white background
white background with clamped L

ANSI generated with delta:

git diff | delta --color-only --syntax-theme='Solarized (dark)' | aha --black
git diff | delta --color-only --syntax-theme='Solarized (dark)' | aha
git diff | delta --color-only --syntax-theme='Solarized (dark)' | aha | python ./dark2light.py
git diff | delta --color-only --syntax-theme='Visual Studio Dark+' | aha --black
git diff | delta --color-only --syntax-theme='Visual Studio Dark+' | aha
git diff | delta --color-only --syntax-theme='Visual Studio Dark+' | aha | python ./dark2light.py

dark-fixed.jpeg

dark-orig.jpeg

dark-white.jpeg

solarized-fixed.jpeg

solarized-orig.jpeg

solarized-white.jpeg