Implement mix and mixp

Author: gravitystorm

lib/glug.rb

@@ -11,4 +11,5 @@ module Glug # :nodoc:
 require_relative 'glug/layer'
 require_relative 'glug/extensions'
 require_relative 'glug/hsluv_modifiers'
+require_relative 'glug/chroma_extensions'
 require_relative 'glug/stylesheet_dsl'

lib/glug/chroma_extensions.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'chroma'
+require 'hsluv'
+
+module Chroma
+  class Color # :nodoc:
+    def mix(other, weight = 50)
+      other = other.paint if other.is_a?(String)
+      p = weight / 100.0
+
+      r = (rgb.r * p + other.rgb.r * (1 - p)).round
+      g = (rgb.g * p + other.rgb.g * (1 - p)).round
+      b = (rgb.b * p + other.rgb.b * (1 - p)).round
+
+      Chroma.paint("rgb(#{r}, #{g}, #{b})")
+    end
+  end
+end

lib/glug/extensions.rb

@@ -5,20 +5,20 @@
 
 # Colour methods on Integer
 class Integer
-  # rubocop:disable Style/StringConcatenation, Naming/MethodParameterName
-  def chroma_hex(op, p = nil)
+  # rubocop:disable Style/StringConcatenation
+  def chroma_hex(op, *args)
     color = ('#' + to_s(16).rjust(6, '0')).paint
-    (p.nil? ? color.send(op) : color.send(op, p)).to_hex
+    color.send(op, *args).to_hex
   end
 
-  def chroma(op, p = nil)
-    chroma_hex(op, p).gsub('#', '0x').to_i(16)
+  def chroma(op, *args)
+    chroma_hex(op, *args).gsub('#', '0x').to_i(16)
   end
 
   def to_hex_color
     '#' + to_s(16).rjust(6, '0')
   end
-  # rubocop:enable Style/StringConcatenation, Naming/MethodParameterName
+  # rubocop:enable Style/StringConcatenation
 end
 
 # Top-level colour generators

lib/glug/hsluv_modifiers.rb

@@ -47,5 +47,25 @@ def spinp(amount = 0)
       rgb_values = Hsluv.rgb_prepare(Hsluv.hsluv_to_rgb(new_h, s, l))
       Chroma.paint("rgb(#{rgb_values[0]}, #{rgb_values[1]}, #{rgb_values[2]})")
     end
+
+    def mixp(other, weight = 50)
+      other = other.paint if other.is_a?(String)
+      p = weight / 100.0
+
+      h1, s1, l1 = Hsluv.rgb_to_hsluv(rgb.r / 255.0, rgb.g / 255.0, rgb.b / 255.0)
+      h2, s2, l2 = Hsluv.rgb_to_hsluv(other.rgb.r / 255.0, other.rgb.g / 255.0, other.rgb.b / 255.0)
+
+      # Interpolate hue on the shortest path around the color wheel
+      h_diff = h2 - h1
+      h_diff -= 360 if h_diff > 180
+      h_diff += 360 if h_diff < -180
+      new_h = (h1 + h_diff * (1 - p)) % 360
+
+      new_s = s1 * p + s2 * (1 - p)
+      new_l = l1 * p + l2 * (1 - p)
+
+      rgb_values = Hsluv.rgb_prepare(Hsluv.hsluv_to_rgb(new_h, new_s, new_l))
+      Chroma.paint("rgb(#{rgb_values[0]}, #{rgb_values[1]}, #{rgb_values[2]})")
+    end
   end
 end

spec/fixtures/color_functions.glug

@@ -49,3 +49,11 @@ end
 layer(:spinp, source: :shortbread) do
   line_color 0x998877.chroma(:spinp, 20)
 end
+
+layer(:mix, source: :shortbread) do
+  line_color 0x998877.chroma(:mix, '#ffffff', 50)
+end
+
+layer(:mixp, source: :shortbread) do
+  line_color 0x998877.chroma(:mixp, '#ffffff', 50)
+end

spec/fixtures/color_functions.json

@@ -91,6 +91,20 @@
       "id":"spinp",
       "source-layer":"spinp",
       "type":"line"
+    },
+    {
+      "paint":{"line-color":"#ccc4bb"},
+      "source":"shortbread",
+      "id":"mix",
+      "source-layer":"mix",
+      "type":"line"
+    },
+    {
+      "paint":{"line-color":"#cdc1be"},
+      "source":"shortbread",
+      "id":"mixp",
+      "source-layer":"mixp",
+      "type":"line"
     }
   ]
 }