From 618cc285d9bd612f4335ef80be490699b03d1d0c Mon Sep 17 00:00:00 2001
From: Leon Heidelbach <leon.heidelbach@hhu.de>
Date: Sat, 4 Jun 2022 19:27:44 +0200
Subject: [PATCH] feat: added custom color library

---
 lua/colors.lua | 163 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 163 insertions(+)
 create mode 100644 lua/colors.lua

diff --git a/lua/colors.lua b/lua/colors.lua
new file mode 100644
index 0000000..0972d6c
--- /dev/null
+++ b/lua/colors.lua
@@ -0,0 +1,163 @@
+M = {}
+
+-- Convert a hex color value to RGB
+-- @param hex: The hex color value
+-- @return r: red (0-255)
+-- @return g: green (0-255)
+-- @return b: blue (0-255)
+M.hex2rgb = function(hex)
+   local hash = string.sub(hex, 1, 1) == "#"
+   if string.len(hex) ~= (7 - (hash and 0 or 1)) then
+      return nil
+   end
+
+   local r = tonumber(hex:sub(2 - (hash and 0 or 1), 3 - (hash and 0 or 1)), 16)
+   local g = tonumber(hex:sub(4 - (hash and 0 or 1), 5 - (hash and 0 or 1)), 16)
+   local b = tonumber(hex:sub(6 - (hash and 0 or 1), 7 - (hash and 0 or 1)), 16)
+   return r, g, b
+end
+
+-- Convert an RGB color value to hex
+-- @param r The red value (0-255)
+-- @param g The green value (0-255)
+-- @param b The blue value (0-255)
+-- @return The hexadecimal string representation of the color
+M.rgb2hex = function(r, g, b)
+   return string.format("#%02x%02x%02x", math.floor(r), math.floor(g), math.floor(b))
+end
+
+-- Helper function to convert a HSL color value to RGB
+-- Not to be used directly, use M.hsl2rgb instead
+M.hsl2rgb_helper = function(p, q, a)
+   if (a < 0) then a = a + 6 end
+   if (a >= 6) then a = a - 6 end
+   if (a < 1) then return (q - p) * a + p
+   elseif (a < 3) then return q
+   elseif (a < 4) then return (q - p) * (4 - a) + p
+   else return p end
+end
+
+-- Convert a HSL color value to RGB
+-- @param h: hue (0-360)
+-- @param s: saturation (0-1)
+-- @param l: lightness (0-1)
+-- @return r: red (0-255)
+-- @return g: green (0-255)
+-- @return b: blue (0-255)
+M.hsl2rgb = function(h, s, l)
+   local t1, t2, r, g, b
+
+   h = h / 60
+   if (l <= 0.5) then
+      t2 = l * (s + 1)
+   else
+      t2 = l + s - (l * s)
+   end
+
+   t1 = l * 2 - t2
+   r = M.hsl2rgb_helper(t1, t2, h + 2) * 255
+   g = M.hsl2rgb_helper(t1, t2, h) * 255
+   b = M.hsl2rgb_helper(t1, t2, h - 2) * 255
+   return r, g, b
+end
+
+-- Convert an RGB color value to HSL
+-- @param r Red (0-255)
+-- @param g Green (0-255)
+-- @param b Blue (0-255)
+-- @return h Hue (0-360)
+-- @return s Saturation (0-1)
+-- @return l Lightness (0-1)
+M.rgb2hsl = function(r, g, b)
+   local min, max, l, s, maxcolor, h
+   r, g, b = r / 255, g / 255, b / 255
+
+   min = math.min(r, g, b)
+   max = math.max(r, g, b)
+   maxcolor = 1 + (max == b and 2 or (max == g and 1 or 0))
+
+   if maxcolor == 1 then h = (g - b) / (max - min) end
+   if maxcolor == 2 then h = 2 + (b - r) / (max - min) end
+   if maxcolor == 3 then h = 4 + (r - g) / (max - min) end
+
+   if not rawequal(type(h), 'number') then h = 0 end
+
+   h = h * 60
+
+   if h < 0 then h = h + 360 end
+
+   l = (min + max) / 2
+
+   if min == max then
+      s = 0
+   else
+      if l < 0.5 then
+         s = (max - min) / (max + min)
+      else
+         s = (max - min) / (2 - max - min)
+      end
+   end
+
+   return h, s, l
+end
+
+-- Convert a hex color value to HSL
+-- @param hex: The hex color value
+-- @return h: Hue
+-- @return s: Saturation
+-- @return l: Lightness
+M.hex2hsl = function(hex)
+   local r, g, b = M.hex2rgb(hex)
+   return M.rgb2hsl(r, g, b)
+end
+
+-- Convert a HSL color value to hex
+-- @param h Hue
+-- @param s Saturation
+-- @param l Lightness
+-- @returns hex color value
+M.hsl2hex = function(h, s, l)
+   local r, g, b = M.hsl2rgb(h, s, l)
+   return M.rgb2hex(r, g, b)
+end
+
+-- Change the hue of a color by a given amount
+-- @param hex The hex color value
+-- @param amount The amount to change the hue.
+--               Negative values decrease the hue, positive values increase it.
+-- @return The hex color value
+M.change_hex_hue = function(hex, percent)
+   local h, s, l = M.hex2hsl(hex)
+   h = h + (percent / 100)
+   if h > 360 then h = 360 end
+   if h < 0 then h = 0 end
+   return M.hsl2hex(h, s, l)
+end
+
+-- Desaturate or saturate a color by a given percentage
+-- @param hex The hex color value
+-- @param percent The percentage to desaturate or saturate the color.
+--                Negative values desaturate the color, positive values saturate it
+-- @return The hex color value
+M.change_hex_saturation = function(hex, percent)
+   local h, s, l = M.hex2hsl(hex)
+   s = s + (percent / 100)
+   if s > 1 then s = 1 end
+   if s < 0 then s = 0 end
+   return M.hsl2hex(h, s, l)
+end
+
+-- Lighten or darken a color by a given percentage
+-- @param hex The hex color value
+-- @param percent The percentage to lighten or darken the color.
+--                Negative values darken the color, positive values lighten it
+-- @return The hex color value
+M.change_hex_lightness = function(hex, percent)
+   local h, s, l = M.hex2hsl(hex)
+   l = l + (percent / 100)
+   if l > 1 then l = 1 end
+   if l < 0 then l = 0 end
+   return M.hsl2hex(h, s, l)
+end
+
+return M