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local oklab = require "prismite.oklab"
local M = {}
function M.lerp(a, b, t)
return a + t * (b - a)
end
function M.mix_oklch(a, b, t)
if not (a.l and a.c and a.h) then
error("`a` must be a valid OKLCH color", 2)
end
if not (b.l and b.c and b.h) then
error("`b` must be a valid OKLCH color", 2)
end
if type(t) ~= "number" then
error("'t' must be a number", 2)
end
local a_h = a.h
local b_h = b.h
-- https://drafts.csswg.org/css-color-4/#hue-shorter
if b_h - a_h > 180 then
print "adjusted +"
a_h = a_h + 360
end
if b_h - a_h < -180 then
print "adjusted -"
b_h = b_h + 360
end
return { l = M.lerp(a.l, b.l, t), c = M.lerp(a.c, b.c, t), h = M.lerp(a_h, b_h, t) }
end
local function over(a, b, alpha)
return a * alpha + b * (1 - alpha)
end
function M.overlay_oklch(a, b, alpha)
if not (a.l and a.c and a.h) then
error("`a` must be a valid OKLCH color", 2)
end
if not (b.l and b.c and b.h) then
error("`b` must be a valid OKLCH color", 2)
end
if type(alpha) ~= "number" then
error("'alpha' must be a number", 2)
end
local a_oklab = oklab.oklch2oklab(a)
local b_oklab = oklab.oklch2oklab(b)
local _l = over(a_oklab.l, b_oklab.l, alpha)
local _a = over(a_oklab.a, b_oklab.a, alpha)
local _b = over(a_oklab.b, b_oklab.b, alpha)
return oklab.oklab2oklch { l = _l, a = _a, b = _b }
end
function M.is_oklch(oklch)
return (oklch.l and oklch.c and oklch.h)
end
function M.oklch2hex(oklch)
return oklab.rgb2hex(oklab.oklab2rgb(oklab.oklch2oklab(oklch)))
end
return M
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