feat: add new option saturation

for #140

Author: scottmckendry

README.md

@@ -158,6 +158,7 @@ require("cyberdream").setup({
 
     theme = {
         variant = "default", -- use "light" for the light variant. Also accepts "auto" to set dark or light colors based on the current value of `vim.o.background`
+        saturation = 1, -- accepts a value between 0 and 1. 0 will be fully desaturated (greyscale) and 1 will be the full color (default)
         highlights = {
             -- Highlight groups to override, adding new groups is also possible
             -- See `:h highlight-groups` for a list of highlight groups or run `:hi` to see all groups and their current values

lua/cyberdream/config.lua

@@ -16,6 +16,7 @@ local M = {}
 
 ---@class ThemeConfig
 ---@field variant? "default" | "light" | "auto"
+---@field saturation? number
 ---@field colors? CyberdreamPalette
 ---@field highlights? table<string, CyberdreamHighlight>
 ---@field overrides? CyberdreamOverrideFn
@@ -71,6 +72,7 @@ local default_options = {
 
     theme = {
         variant = "default",
+        saturation = 1,
         colors = {},
         highlights = {},
     },

lua/cyberdream/theme.lua

@@ -1,4 +1,5 @@
 local colors = require("cyberdream.colors")
+local util = require("cyberdream.util")
 
 local M = {}
 function M.setup()
@@ -20,6 +21,9 @@ function M.setup()
         end
     end
 
+    -- Apply user defined saturation
+    t = util.apply_saturation(t, opts.theme.saturation)
+
     -- Override colors with user defined colors
     ---@type CyberdreamPalette
     t = vim.tbl_deep_extend("force", t, opts.theme.colors)

lua/cyberdream/util.lua

@@ -1,6 +1,9 @@
 local config = require("cyberdream.config")
 local M = {}
 
+--- @alias RGB table {number, number, number}
+--- @alias HSL table {number, number, number}
+
 --- Notify the user with a message.
 --- @param message string
 --- @param level? "info" | "warn" | "error"
@@ -21,6 +24,129 @@ function M.syntax(syntax)
     end
 end
 
+--- Convert a hex color to an RGB color.
+--- @param hex string "#rrggbb"
+--- @return RGB
+function M.hex_to_rgb(hex)
+    return {
+        tonumber(hex:sub(2, 3), 16),
+        tonumber(hex:sub(4, 5), 16),
+        tonumber(hex:sub(6, 7), 16),
+    }
+end
+
+--- Convert an RGB color to a hex color.
+--- @param rgb RGB
+--- @return string
+function M.rgb_to_hex(rgb)
+    return string.format("#%02x%02x%02x", rgb[1], rgb[2], rgb[3])
+end
+
+--- Convert an HSL color to RGB.
+--- @param HSL HSL
+--- @return RGB
+function M.hsl_to_rgb(HSL)
+    local h, s, l = HSL[1] / 360, HSL[2] / 100, HSL[3] / 100
+    local r, g, b
+
+    if s == 0 then
+        r, g, b = l, l, l
+    else
+        local function hue_to_rgb(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 = l < 0.5 and l * (1 + s) or l + s - l * s
+        local p = 2 * l - q
+        r = hue_to_rgb(p, q, h + 1 / 3)
+        g = hue_to_rgb(p, q, h)
+        b = hue_to_rgb(p, q, h - 1 / 3)
+    end
+
+    return { r * 255, g * 255, b * 255 }
+end
+
+--- Convert an RGB color to HSL.
+--- @param RGB RGB
+--- @return HSL
+function M.rgb_to_hsl(RGB)
+    local r, g, b = RGB[1] / 255, RGB[2] / 255, RGB[3] / 255
+    local max, min = math.max(r, g, b), math.min(r, g, b)
+    local h, s, l
+
+    l = (max + min) / 2
+
+    if max == min then
+        h, s = 0, 0
+    else
+        local d = max - min
+        s = l > 0.5 and d / (2 - max - min) or d / (max + min)
+        if max == r then
+            h = (g - b) / d + (g < b and 6 or 0)
+        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
+
+--- Desaturate an HSL color based on a float. 0 is fully desaturated, 1 is the original color.
+--- @param HSL HSL
+--- @param weight number
+--- @return HSL
+function M.desaturate(HSL, weight)
+    weight = weight or 0.5
+    HSL[2] = HSL[2] * weight
+    return HSL
+end
+
+--- Desaturate a hex color based on a float. 0 is fully desaturated, 1 is the original color.
+function M.desaturate_hex(hex, weight)
+    local rgb = M.hex_to_rgb(hex)
+    local hsl = M.rgb_to_hsl(rgb)
+    local desaturated_hsl = M.desaturate(hsl, weight)
+    local desaturated_rgb = M.hsl_to_rgb(desaturated_hsl)
+    return string.format("#%02x%02x%02x", desaturated_rgb[1], desaturated_rgb[2], desaturated_rgb[3])
+end
+
+--- Apply saturation to a table of colors.
+--- @param colors CyberdreamColorLight | CyberdreamColorDefault
+--- @param weight number
+function M.apply_saturation(colors, weight)
+    if weight >= 1 then
+        return colors
+    end
+
+    if weight < 0 then
+        weight = 0
+    end
+
+    local desaturated_colors = {}
+    for k, v in pairs(colors) do
+        desaturated_colors[k] = M.desaturate_hex(v, weight)
+    end
+    return desaturated_colors
+end
+
 --- Load the colorscheme.
 --- @param theme table
 function M.load(theme)
@@ -43,8 +169,8 @@ end
 function M.blend(color1, color2, weight)
     weight = weight or 0.5
 
-    local rgb1 = { tonumber(color1:sub(2, 3), 16), tonumber(color1:sub(4, 5), 16), tonumber(color1:sub(6, 7), 16) }
-    local rgb2 = { tonumber(color2:sub(2, 3), 16), tonumber(color2:sub(4, 5), 16), tonumber(color2:sub(6, 7), 16) }
+    local rgb1 = M.hex_to_rgb(color1)
+    local rgb2 = M.hex_to_rgb(color2)
     local rgb_blended = {}
     for i = 1, 3 do
         rgb_blended[i] = math.floor(rgb1[i] * weight + rgb2[i] * (1 - weight))