Add initial prototype.

3-mid/opengl/source/lean/opengl-palette.adb

@@ -0,0 +1,67 @@
+with
+     ada.Numerics.discrete_Random;
+
+
+package body openGL.Palette
+is
+   package random_Colors is new ada.Numerics.discrete_Random (Color_Value);
+   use     random_Colors;
+
+   the_Generator : random_Colors.Generator;
+
+
+
+   function random_Color return Color
+   is
+   begin
+      return +(random (the_Generator),
+               random (the_Generator),
+               random (the_Generator));
+   end random_Color;
+
+
+
+   function Shade_of (Self : in Color;   Level : in Shade_Level) return Color
+   is
+   begin
+      return (Self.Red   * Primary (Level),
+              Self.Green * Primary (Level),
+              Self.Blue  * Primary (Level));
+   end Shade_of;
+
+
+
+   function Mixed (Self : in Color;   Other : in Color;
+                                      Mix   : in mix_Factor := 0.5) return Color
+   is
+      function Interpolate (Value_1, Value_2 : in Primary) return Primary     -- Linear interpolate.
+      is
+      begin
+         return    Value_1
+                + (Value_2 - Value_1) * Primary (Mix);
+      end Interpolate;
+
+   begin
+      return (Interpolate (Self.Red,   Other.Red),
+              Interpolate (Self.Green, Other.Green),
+              Interpolate (Self.Blue,  Other.Blue));
+   end Mixed;
+
+
+
+   function is_Similar (Self : in Color;   To         : in Color;
+                                           Similarity : in Primary := default_Similarity) return Boolean
+   is
+   begin
+      return     Self.Red   <= to.Red   + Similarity
+        and then Self.Red   >= to.Red   - Similarity
+        and then Self.Green <= to.Green + Similarity
+        and then Self.Green >= to.Green - Similarity
+        and then Self.Blue  <= to.Blue  + Similarity
+        and then Self.Blue  >= to.Blue  - Similarity;
+   end is_Similar;
+
+
+begin
+   reset (the_Generator);
+end openGL.Palette;