How to highlight HSL colors with `mini.hipatterns`

editor.lua

-- plugins/editor.lua
return {
	{
		"echasnovski/mini.hipatterns",
		event = "BufReadPre",
		opts = {
			highlighters = {
				hsl_color = {
					pattern = "hsl%(%d+,? %d+,? %d+%)",
					group = function(_, match)
						local utils = require("craftzdog.utils")
						local h, s, l = match:match("hsl%((%d+),? (%d+),? (%d+)%)")
						h, s, l = tonumber(h), tonumber(s), tonumber(l)
						local hex_color = utils.hslToHex(h, s, l)
						return MiniHipatterns.compute_hex_color_group(hex_color, "bg")
					end,
				},
			},
		},
	},
}

utils.lua

-- craftzdog/utils.lua
-- https://github.com/EmmanuelOga/columns/blob/master/utils/color.lua

local M = {}

local hexChars = "0123456789abcdef"

function M.hex_to_rgb(hex)
	hex = string.lower(hex)
	local ret = {}
	for i = 0, 2 do
		local char1 = string.sub(hex, i * 2 + 2, i * 2 + 2)
		local char2 = string.sub(hex, i * 2 + 3, i * 2 + 3)
		local digit1 = string.find(hexChars, char1) - 1
		local digit2 = string.find(hexChars, char2) - 1
		ret[i + 1] = (digit1 * 16 + digit2) / 255.0
	end
	return ret
end

--[[
 * Converts an RGB color value to HSL. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes r, g, and b are contained in the set [0, 255] and
 * returns h, s, and l in the set [0, 1].
 *
 * @param   Number  r       The red color value
 * @param   Number  g       The green color value
 * @param   Number  b       The blue color value
 * @return  Array           The HSL representation
]]
function M.rgbToHsl(r, g, b)
	local max, min = math.max(r, g, b), math.min(r, g, b)
	local h = 0
	local s = 0
	local l = 0

	l = (max + min) / 2

	if max == min then
		h, s = 0, 0 -- achromatic
	else
		local d = max - min
		if l > 0.5 then
			s = d / (2 - max - min)
		else
			s = d / (max + min)
		end
		if max == r then
			h = (g - b) / d
			if g < b then
				h = h + 6
			end
		elseif max == g then
			h = (b - r) / d + 2
		elseif max == b then
			h = (r - g) / d + 4
		end
		h = h / 6
	end

	return h * 360, s * 100, l * 100
end

--[[
 * Converts an HSL color value to RGB. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes h, s, and l are contained in the set [0, 1] and
 * returns r, g, and b in the set [0, 255].
 *
 * @param   Number  h       The hue
 * @param   Number  s       The saturation
 * @param   Number  l       The lightness
 * @return  Array           The RGB representation
]]
function M.hslToRgb(h, s, l)
	local r, g, b

	if s == 0 then
		r, g, b = l, l, l -- achromatic
	else
		function hue2rgb(p, q, t)
			if t < 0 then
				t = t + 1
			end
			if t > 1 then
				t = t - 1
			end
			if t < 1 / 6 then
				return p + (q - p) * 6 * t
			end
			if t < 1 / 2 then
				return q
			end
			if t < 2 / 3 then
				return p + (q - p) * (2 / 3 - t) * 6
			end
			return p
		end

		local q
		if l < 0.5 then
			q = l * (1 + s)
		else
			q = l + s - l * s
		end
		local p = 2 * l - q

		r = hue2rgb(p, q, h + 1 / 3)
		g = hue2rgb(p, q, h)
		b = hue2rgb(p, q, h - 1 / 3)
	end

	return r * 255, g * 255, b * 255
end

function M.hexToHSL(hex)
	local hsluv = require("solarized-osaka.hsluv")
	local rgb = M.hex_to_rgb(hex)
	local h, s, l = M.rgbToHsl(rgb[1], rgb[2], rgb[3])

	return string.format("hsl(%d, %d, %d)", math.floor(h + 0.5), math.floor(s + 0.5), math.floor(l + 0.5))
end

--[[
 * Converts an HSL color value to RGB in Hex representation.
 * @param   Number  h       The hue
 * @param   Number  s       The saturation
 * @param   Number  l       The lightness
 * @return  String           The hex representation
]]
function M.hslToHex(h, s, l)
	local r, g, b = M.hslToRgb(h / 360, s / 100, l / 100)

	return string.format("#%02x%02x%02x", r, g, b)
end

function M.replaceHexWithHSL()
	-- Get the current line number
	local line_number = vim.api.nvim_win_get_cursor(0)[1]

	-- Get the line content
	local line_content = vim.api.nvim_buf_get_lines(0, line_number - 1, line_number, false)[1]

	-- Find hex code patterns and replace them
	for hex in line_content:gmatch("#[0-9a-fA-F]+") do
		local hsl = M.hexToHSL(hex)
		line_content = line_content:gsub(hex, hsl)
	end

	-- Set the line content back
	vim.api.nvim_buf_set_lines(0, line_number - 1, line_number, false, { line_content })
end

return M

Hi !

Sorry to bother you, I'm also interested in this feature and can't make it work.
I've used your code mini.hipatterns config as it is (I've only just put the used functions hslToRgb and hslToHex inside the same lua file, in order to not used a utils module).
With vim.inspect, I manage to print the HEX color computed from each line with the HSL pattern, and that is correct (more or less, but I think there are only rounding approx, which is fine for me).
Nevertheless, I can't get any higlighting working.
On the
return MiniHipatterns.compute_hex_color_group(hex_color, "bg")
I have a warning Undefined global 'MiniHiPatterns'.. I can't understand how is this line working, maybe that could be the source of my problem ?

Is this gist working as it is ?
After that, I want to update the pattern to make it work for string such as "100 15.1% 10%" (without any hsl()) that you can find in nextjs/shadcn themes for example.

Thanks a lot !

[...] On the return MiniHipatterns.compute_hex_color_group(hex_color, "bg") I have a warning Undefined global 'MiniHiPatterns'.. I can't understand how is this line working, maybe that could be the source of my problem ?

In the original snippet, MiniHiPatterns is the plugin mini.patterns assigned to a variable.
Its definition isn't in the gist, which is why you're seeing an error.

You should define it yourself in the group function (or wherever else you need it):

group = function(_, match)
  local MiniHiPatterns = require('mini.hipatterns')`
  -- ...rest of function
end