path: root/lua/prismite/oklab.lua

-- Source: https://github.com/ramojus/mellifluous.nvim/blob/9add9975a067e448da077dab92b70473aab41a76/lua/mellifluous/utils/oklab.lua
-- modifications:
-- - lightness calculation adjustments: https://github.com/echasnovski/mini.nvim/issues/1628#issuecomment-2692645938
-- - chroma normalization

-- MIT License
--
-- Copyright (c) 2024 Ramojus Lapinskas
--
-- Permission is hereby granted, free of charge, to any person obtaining a copy
-- of this software and associated documentation files (the "Software"), to deal
-- in the Software without restriction, including without limitation the rights
-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-- copies of the Software, and to permit persons to whom the Software is
-- furnished to do so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.

-- Oklab color space: https://bottosson.github.io/posts/oklab/

-- Original code taken from:
-- https://github.com/echasnovski/mini.colors/blob/main/lua/mini/colors.lua,
-- then slightly refactored and restyled to fit project coding style.
-- Parts of code unrelated to conversion of colors were removed.

local M = {}

local tau = 2 * math.pi

-- Cusps for Oklch color space. These represent (c, l) points of Oklch space
-- (with **not corrected lightness**) inside a hue leaf (points with
-- `math.floor(h) = <index>`) with the highest value of chroma (`c`).
-- They are used to model the whole RGB gamut (region inside which sRGB colors
-- are converted in Oklch space). It is modelled as triangle with vertices:
-- (0, 0), (0, 100) and cusp. NOTE: this is an approximation, i.e. not all RGB
-- colors lie inside this triangle **AND** not all points inside triangle are
-- RGB colors. But both proportions are small: around 0.5% with similar modeled
-- RGB color for first one and around 2.16% for second one.
--stylua: ignore start
---@diagnostic disable start
---@private
local cusps = {
        [0] = { 26.23, 64.74 },
    { 26.14, 64.65 },
    { 26.06, 64.56 },
    { 25.98, 64.48 },
    { 25.91, 64.39 },
    { 25.82, 64.29 },
    { 25.76, 64.21 },
    { 25.70, 64.13 },
    { 25.65, 64.06 },
    { 25.59, 63.97 },
    { 25.55, 63.90 },
    { 25.52, 63.83 },
    { 25.48, 63.77 },
    { 25.45, 63.69 },
    { 25.43, 63.63 },
    { 25.41, 63.55 },
    { 25.40, 63.50 },
    { 25.39, 63.43 },
    { 25.40, 63.33 },
    { 25.40, 63.27 },
    { 25.42, 63.22 },
    { 25.44, 63.15 },
    { 25.46, 63.11 },
    { 25.50, 63.05 },
    { 25.53, 63.00 },
    { 25.58, 62.95 },
    { 25.63, 62.90 },
    { 25.69, 62.85 },
    { 25.75, 62.81 },
    { 25.77, 62.80 },
    { 25.34, 63.25 },
    { 24.84, 63.79 },
    { 24.37, 64.32 },
    { 23.92, 64.83 },
    { 23.48, 65.35 },
    { 23.08, 65.85 },
    { 22.65, 66.38 },
    { 22.28, 66.86 },
    { 21.98, 67.27 },
    { 21.67, 67.70 },
    { 21.36, 68.14 },
    { 21.05, 68.60 },
    { 20.74, 69.08 },
    { 20.50, 69.45 },
    { 20.27, 69.83 },
    { 20.04, 70.22 },
    { 19.82, 70.62 },
    { 19.60, 71.03 },
    { 19.38, 71.44 },
    { 19.17, 71.87 },
    { 19.03, 72.16 },
    { 18.83, 72.59 },
    { 18.71, 72.89 },
    { 18.52, 73.34 },
    { 18.40, 73.64 },
    { 18.28, 73.95 },
    { 18.17, 74.26 },
    { 18.01, 74.74 },
    { 17.91, 75.05 },
    { 17.82, 75.38 },
    { 17.72, 75.70 },
    { 17.64, 76.03 },
    { 17.56, 76.36 },
    { 17.48, 76.69 },
    { 17.41, 77.03 },
    { 17.35, 77.36 },
    { 17.29, 77.71 },
    { 17.24, 78.05 },
    { 17.19, 78.39 },
    { 17.15, 78.74 },
    { 17.12, 79.09 },
    { 17.09, 79.45 },
    { 17.07, 79.80 },
    { 17.05, 80.16 },
    { 17.04, 80.52 },
    { 17.04, 81.06 },
    { 17.04, 81.42 },
    { 17.05, 81.79 },
    { 17.07, 82.16 },
    { 17.08, 82.53 },
    { 17.11, 82.72 },
    { 17.14, 83.09 },
    { 17.18, 83.46 },
    { 17.22, 83.84 },
    { 17.27, 84.22 },
    { 17.33, 84.60 },
    { 17.39, 84.98 },
    { 17.48, 85.56 },
    { 17.56, 85.94 },
    { 17.64, 86.33 },
    { 17.73, 86.72 },
    { 17.81, 87.10 },
    { 17.91, 87.50 },
    { 18.04, 88.09 },
    { 18.16, 88.48 },
    { 18.27, 88.88 },
    { 18.40, 89.48 },
    { 18.57, 89.87 },
    { 18.69, 90.27 },
    { 18.88, 90.87 },
    { 19.03, 91.48 },
    { 19.22, 91.88 },
    { 19.44, 92.49 },
    { 19.66, 93.10 },
    { 19.85, 93.71 },
    { 20.04, 94.33 },
    { 20.33, 94.94 },
    { 20.60, 95.56 },
    { 20.85, 96.18 },
    { 21.10, 96.80 },
    { 21.19, 96.48 },
    { 21.27, 96.24 },
    { 21.38, 95.93 },
    { 21.47, 95.70 },
    { 21.59, 95.40 },
    { 21.72, 95.10 },
    { 21.86, 94.80 },
    { 21.97, 94.58 },
    { 22.12, 94.30 },
    { 22.27, 94.02 },
    { 22.43, 93.74 },
    { 22.64, 93.40 },
    { 22.81, 93.14 },
    { 23.04, 92.81 },
    { 23.22, 92.56 },
    { 23.45, 92.25 },
    { 23.68, 91.95 },
    { 23.92, 91.65 },
    { 24.21, 91.31 },
    { 24.45, 91.04 },
    { 24.74, 90.72 },
    { 25.08, 90.36 },
    { 25.37, 90.07 },
    { 25.70, 89.74 },
    { 26.08, 89.39 },
    { 26.44, 89.07 },
    { 26.87, 88.69 },
    { 27.27, 88.34 },
    { 27.72, 87.98 },
    { 28.19, 87.61 },
    { 28.68, 87.23 },
    { 29.21, 86.84 },
    { 29.48, 86.64 },
    { 28.99, 86.70 },
    { 28.13, 86.81 },
    { 27.28, 86.92 },
    { 26.56, 87.02 },
    { 25.83, 87.12 },
    { 25.18, 87.22 },
    { 24.57, 87.32 },
    { 24.01, 87.41 },
    { 23.53, 87.49 },
    { 23.03, 87.58 },
    { 22.53, 87.68 },
    { 22.10, 87.76 },
    { 21.68, 87.84 },
    { 21.26, 87.93 },
    { 20.92, 88.01 },
    { 20.58, 88.08 },
    { 20.25, 88.16 },
    { 19.92, 88.24 },
    { 19.59, 88.33 },
    { 19.35, 88.39 },
    { 19.12, 88.46 },
    { 18.81, 88.55 },
    { 18.58, 88.61 },
    { 18.36, 88.68 },
    { 18.14, 88.76 },
    { 17.93, 88.83 },
    { 17.79, 88.88 },
    { 17.59, 88.95 },
    { 17.39, 89.03 },
    { 17.26, 89.08 },
    { 17.08, 89.16 },
    { 16.96, 89.21 },
    { 16.79, 89.29 },
    { 16.68, 89.35 },
    { 16.58, 89.41 },
    { 16.43, 89.49 },
    { 16.33, 89.55 },
    { 16.24, 89.60 },
    { 16.16, 89.66 },
    { 16.04, 89.75 },
    { 15.96, 89.81 },
    { 15.89, 89.87 },
    { 15.83, 89.93 },
    { 15.77, 89.99 },
    { 15.71, 90.05 },
    { 15.66, 90.12 },
    { 15.61, 90.18 },
    { 15.57, 90.24 },
    { 15.54, 90.31 },
    { 15.51, 90.37 },
    { 15.48, 90.44 },
    { 15.46, 90.51 },
    { 15.40, 90.30 },
    { 15.30, 89.83 },
    { 15.21, 89.36 },
    { 15.12, 88.89 },
    { 15.03, 88.67 },
    { 14.99, 88.18 },
    { 14.92, 87.71 },
    { 14.85, 87.24 },
    { 14.78, 86.77 },
    { 14.75, 86.53 },
    { 14.70, 86.06 },
    { 14.65, 85.59 },
    { 14.61, 85.12 },
    { 14.60, 84.89 },
    { 14.57, 84.42 },
    { 14.54, 83.94 },
    { 14.53, 83.71 },
    { 14.52, 83.24 },
    { 14.51, 82.77 },
    { 14.52, 82.30 },
    { 14.52, 81.83 },
    { 14.53, 81.60 },
    { 14.55, 81.13 },
    { 14.58, 80.66 },
    { 14.59, 80.43 },
    { 14.63, 79.96 },
    { 14.68, 79.49 },
    { 14.70, 79.26 },
    { 14.76, 78.79 },
    { 14.82, 78.32 },
    { 14.85, 78.09 },
    { 14.93, 77.62 },
    { 15.01, 77.16 },
    { 15.10, 76.69 },
    { 15.19, 76.23 },
    { 15.24, 76.00 },
    { 15.34, 75.54 },
    { 15.45, 75.07 },
    { 15.57, 74.61 },
    { 15.69, 74.15 },
    { 15.82, 73.69 },
    { 15.96, 73.23 },
    { 16.10, 72.77 },
    { 16.24, 72.31 },
    { 16.39, 71.86 },
    { 16.55, 71.40 },
    { 16.71, 70.95 },
    { 16.96, 70.26 },
    { 17.14, 69.81 },
    { 17.32, 69.36 },
    { 17.59, 68.69 },
    { 17.88, 68.02 },
    { 18.07, 67.57 },
    { 18.37, 66.90 },
    { 18.67, 66.24 },
    { 18.99, 65.58 },
    { 19.30, 64.93 },
    { 19.74, 64.06 },
    { 20.07, 63.42 },
    { 20.51, 62.57 },
    { 20.97, 61.73 },
    { 21.54, 60.69 },
    { 22.00, 59.87 },
    { 22.70, 58.66 },
    { 23.39, 57.49 },
    { 24.19, 56.16 },
    { 25.20, 54.52 },
    { 26.38, 52.66 },
    { 28.55, 49.32 },
    { 31.32, 45.20 },
    { 31.15, 45.42 },
    { 30.99, 45.64 },
    { 30.85, 45.85 },
    { 30.72, 46.06 },
    { 30.57, 46.31 },
    { 30.47, 46.50 },
    { 30.34, 46.75 },
    { 30.23, 46.97 },
    { 30.13, 47.20 },
    { 30.03, 47.45 },
    { 29.93, 47.71 },
    { 29.86, 47.91 },
    { 29.77, 48.20 },
    { 29.71, 48.43 },
    { 29.65, 48.66 },
    { 29.58, 48.98 },
    { 29.53, 49.23 },
    { 29.48, 49.48 },
    { 29.44, 49.74 },
    { 29.41, 50.01 },
    { 29.37, 50.29 },
    { 29.35, 50.57 },
    { 29.33, 50.86 },
    { 29.31, 51.16 },
    { 29.30, 51.56 },
    { 29.29, 51.87 },
    { 29.29, 52.39 },
    { 29.30, 52.72 },
    { 29.31, 53.05 },
    { 29.33, 53.38 },
    { 29.35, 53.72 },
    { 29.37, 54.06 },
    { 29.40, 54.41 },
    { 29.43, 54.76 },
    { 29.47, 55.12 },
    { 29.52, 55.60 },
    { 29.56, 55.97 },
    { 29.61, 56.34 },
    { 29.66, 56.72 },
    { 29.73, 57.22 },
    { 29.79, 57.61 },
    { 29.84, 57.99 },
    { 29.93, 58.52 },
    { 29.99, 58.91 },
    { 30.08, 59.44 },
    { 30.15, 59.84 },
    { 30.24, 60.38 },
    { 30.34, 60.93 },
    { 30.42, 61.34 },
    { 30.52, 61.90 },
    { 30.63, 62.45 },
    { 30.73, 63.02 },
    { 30.85, 63.58 },
    { 30.96, 64.15 },
    { 31.08, 64.72 },
    { 31.19, 65.30 },
    { 31.31, 65.88 },
    { 31.44, 66.46 },
    { 31.59, 67.20 },
    { 31.72, 67.79 },
    { 31.88, 68.53 },
    { 32.01, 69.12 },
    { 32.18, 69.87 },
    { 32.25, 70.17 },
    { 32.06, 69.99 },
    { 31.76, 69.70 },
    { 31.45, 69.42 },
    { 31.21, 69.20 },
    { 30.97, 68.98 },
    { 30.68, 68.71 },
    { 30.44, 68.50 },
    { 30.21, 68.29 },
    { 29.98, 68.09 },
    { 29.75, 67.89 },
    { 29.53, 67.69 },
    { 29.31, 67.50 },
    { 29.09, 67.31 },
    { 28.88, 67.12 },
    { 28.72, 66.98 },
    { 28.52, 66.80 },
    { 28.31, 66.63 },
    { 28.16, 66.50 },
    { 27.97, 66.33 },
    { 27.78, 66.17 },
    { 27.64, 66.05 },
    { 27.49, 65.94 },
    { 27.33, 65.77 },
    { 27.20, 65.66 },
    { 27.04, 65.51 },
    { 26.92, 65.40 },
    { 26.81, 65.30 },
    { 26.66, 65.16 },
    { 26.55, 65.06 },
    { 26.45, 64.96 },
    { 26.35, 64.87 },
}

local function cuberoot(x)
    return math.pow(x, 1 / 3)
end

local function correct_channel(x)
    return 0.04045 < x and math.pow((x + 0.055) / 1.055, 2.4) or (x / 12.92)
end

local function correct_channel_inv(x)
    return (0.0031308 >= x) and (12.92 * x) or (1.055 * math.pow(x, 0.416666667) - 0.055)
end

local function clip(x, from, to)
    return math.min(math.max(x, from), to)
end

local function round(x)
    return math.floor(x + 0.5)
end

local function degree2rad(x)
    return (x % 360) * tau / 360
end

local function rad2degree(x)
    return (x % tau) * 360 / tau
end

local function correct_lightness(x)
    x = 0.01 * x
    local k1, k2 = 0.206, 0.03
    local k3 = (1 + k1) / (1 + k2)

    local res = 0.5 * (k3 * x - k1 + math.sqrt((k3 * x - k1) ^ 2 + 4 * k2 * k3 * x))
    return 100 * res
end

local function correct_lightness_inv(x)
    x = 0.01 * x
    local k1, k2 = 0.206, 0.03
    local k3 = (1 + k1) / (1 + k2)
    local res = (x / k3) * (x + k1) / (x + k2)
    return 100 * res
end

-- Get gamut ranges for Lch point. They are computed for its hue leaf as
-- segments of triangle in (c, l) coordinates ((0, 0), (0, 100), cusp).
-- Equations for triangle parts:
-- - Lower segment ((0; 0) to cusp): y * c_cusp = x * L_cusp
-- - Upper segment ((0; 100) to cusp): (100 - y) * c_cusp = x * (100 - L_cusp)
-- NOTEs:
-- - It is **very important** that this triangle is computed for **not
--   corrected** lightness. But it is assumed **corrected lightness** in input.
-- - This approach is not entirely accurate and can results in ranges outside
--   of input `lch` for in-gamut point. Put it should be pretty rare: ~0.5%
--   cases for most saturated colors.
local function get_gamut_points(lch)
    local c, l = lch.c, clip(lch.l, 0, 100)
    l = correct_lightness_inv(l)
    local cusp = cusps[math.floor(lch.h % 360)]
    local c_cusp, l_cusp = cusp[1], cusp[2]

    -- Maximum allowed chroma is computed based on current lightness and depends
    -- on whether `l` is below or above cusp's `l`:
    -- - If below, then it is from lower triangle segment.
    -- - If above - from upper segment.
    local c_upper = l <= l_cusp and (c_cusp * l / l_cusp) or (c_cusp * (100 - l) / (100 - l_cusp))
    -- - Don't allow negative chroma (can happen if `l` is out of [0; 100])
    c_upper = clip(c_upper, 0, math.huge)

    -- Other points can be computed only in presence of actual chroma
    if c == nil then return { c_upper = c_upper } end

    -- Range of allowed lightness is computed based on current chroma:
    -- - Lower is from segment between (0, 0) and cusp.
    -- - Upper is from segment between (0, 100) and cusp.
    local l_lower, l_upper
    if c < 0 then
        l_lower, l_upper = 0, 100
    elseif c_cusp < c then
        l_lower, l_upper = l_cusp, l_cusp
    else
        local saturation = c / c_cusp
        l_lower = saturation * l_cusp
        l_upper = saturation * (l_cusp - 100) + 100
    end

    -- Intersection of segment between (c, l) and (0, l_cusp) with gamut boundary
    local c_cusp_clip, l_cusp_clip
    if c <= 0 then
        c_cusp_clip, l_cusp_clip = c, l
    elseif l <= l_cusp then
        -- Intersection with lower segment
        local prop = 1 - l / l_cusp
        c_cusp_clip = c_cusp * c / (c_cusp * prop + c)
        l_cusp_clip = l_cusp * c_cusp_clip / c_cusp
    else
        -- Intersection with upper segment
        local prop = 1 - (l - 100) / (l_cusp - 100)
        c_cusp_clip = c_cusp * c / (c_cusp * prop + c)
        l_cusp_clip = 100 + c_cusp_clip * (l_cusp - 100) / c_cusp
    end

    return {
        l_lower = correct_lightness(l_lower),
        l_upper = correct_lightness(l_upper),
        c_upper = c_upper,
        l_cusp_clip = correct_lightness(l_cusp_clip),
        c_cusp_clip = c_cusp_clip,
    }
end

function M.oklch2okhsl(lch)
    if lch.c <= 0 or lch.h == nil then return { l = lch.l, s = 0 } end

    local gamut_points = get_gamut_points(lch)
    local percent = 100 * lch.c / gamut_points.c_upper

    return { l = lch.l, s = clip(percent, 0, 100), h = lch.h }
end

function M.okhsl2oklch(lsh)
    if lsh.s <= 0 or lsh.h == nil then return { l = lsh.l, c = 0 } end

    local gamut_points = get_gamut_points(lsh)
    local c = 0.01 * lsh.s * gamut_points.c_upper

    return { l = lsh.l, c = clip(c, 0, math.huge), h = lsh.h }
end

function M.oklab2oklch(lab)
    local c = math.sqrt(lab.a ^ 2 + lab.b ^ 2)
    -- Treat grays specially
    local h = nil
    if c > 0 then h = rad2degree(math.atan2(lab.b, lab.a)) end
    return { l = lab.l, c = c, h = h }
end

function M.oklch2oklab(lch)
    -- Treat grays specially
    if lch.c <= 0 or lch.h == nil then return { l = lch.l, a = 0, b = 0 } end

    local a = lch.c * math.cos(degree2rad(lch.h))
    local b = lch.c * math.sin(degree2rad(lch.h))
    return { l = lch.l, a = a, b = b }
end

function M.rgb2oklab(rgb)
    -- Convert to linear RGB
    local r, g, b = correct_channel(rgb.r / 255), correct_channel(rgb.g / 255), correct_channel(rgb.b / 255)

    -- Convert to Oklab
    local l = 0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b
    local m = 0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b
    local s = 0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b

    local l_, m_, s_ = cuberoot(l), cuberoot(m), cuberoot(s)

    local L = 0.2104542553 * l_ + 0.7936177850 * m_ - 0.0040720468 * s_
    local A = 1.9779984951 * l_ - 2.4285922050 * m_ + 0.4505937099 * s_
    local B = 0.0259040371 * l_ + 0.7827717662 * m_ - 0.8086757660 * s_

    -- Explicitly convert for nearly achromatic colors
    if math.abs(A) < 1e-4 then A = 0 end
    if math.abs(B) < 1e-4 then B = 0 end

    -- Normalize to appropriate range
    return { l = 100 * L, a = A, b = B }
end

function M.oklab2rgb(oklab)
    local L, A, B = 0.01 * oklab.l, oklab.a, oklab.b

    local l_ = L + 0.3963377774 * A + 0.2158037573 * B
    local m_ = L - 0.1055613458 * A - 0.0638541728 * B
    local s_ = L - 0.0894841775 * A - 1.2914855480 * B

    local l = l_ * l_ * l_
    local m = m_ * m_ * m_
    local s = s_ * s_ * s_

    --stylua: ignore
    local r = 4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s
    local g = -1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s
    local b = -0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s

    return { r = 255 * correct_channel_inv(r), g = 255 * correct_channel_inv(g), b = 255 * correct_channel_inv(b) }
end

function M.hex2rgb(hex)
    local dec = tonumber(hex:sub(2), 16)

    local b = math.fmod(dec, 256)
    local g = math.fmod((dec - b) / 256, 256)
    local r = math.floor(dec / 65536)

    return { r = r, g = g, b = b }
end

function M.rgb2hex(rgb)
    -- Use straightforward clipping to [0; 255] here to ensure correctness.
    -- Modify `rgb` prior to this to ensure only a small distortion.
    local r = clip(round(rgb.r), 0, 255)
    local g = clip(round(rgb.g), 0, 255)
    local b = clip(round(rgb.b), 0, 255)

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

return M