feat(color): add Hue enum, closestHue*() fns, namedHueRgba()

packages/color/src/api.ts

@@ -53,8 +53,25 @@ export const YELLOW = Object.freeze([1, 1, 0, 1]);
 
 export const RGB_LUMINANCE = [0.299, 0.587, 0.114];
 
-export const SRGB_GAMMA = 1.0 / 2.2;
-export const SRGB_INVERSE_GAMMA = 2.2;
+// Hue names
+
+export enum Hue {
+    RED,
+    ORANGE,
+    YELLOW,
+    CHARTREUSE,
+    GREEN,
+    SPRING_GREEN,
+    CYAN,
+    AZURE,
+    BLUE,
+    VIOLET,
+    MAGENTA,
+    ROSE
+}
+
+// internal helpers
+
 export const SRGB_ALPHA = 0.055;
 
 export const RGB_XYZ = [
@@ -69,8 +86,6 @@ export const XYZ_RGB = [
     0.0556434, -0.2040259, 1.0572252
 ];
 
-// internal helpers
-
 export const FF = float(2);
 export const PC = percent(2);
 export const INV8BIT = 1 / 0xff;

packages/color/src/closest-hue.ts

@@ -0,0 +1,20 @@
+import { Hue } from "./api";
+import { ensureHue } from "./internal/ensure-hue";
+
+/**
+ * Returns the `Hue` constant of the closest of 12 defined hues.
+ *
+ * @param h hue
+ */
+export const closestHue =
+    (h: number): Hue =>
+        Math.round(ensureHue(h) * 12) % 12;
+
+/**
+ * Returns the `Hue` constant of the closest primary or secondary hue.
+ *
+ * @param h
+ */
+export const closestPrimaryHue =
+    (h: number): Hue =>
+        (Math.round(ensureHue(h) * 12) % 12) & 0xe;

packages/color/src/hue-rgba.ts

@@ -1,6 +1,6 @@
 import { clamp01 } from "@thi.ng/math/interval";
 import { setC4 } from "@thi.ng/vectors3/setc";
-import { Color } from "./api";
+import { Color, Hue } from "./api";
 import { ensureHue } from "./internal/ensure-hue";
 
 /**
@@ -21,3 +21,7 @@ export const hueRgba =
             alpha
         );
     };
+
+export const namedHueRgba =
+    (out: Color, hue: Hue, alpha = 1) =>
+        hueRgba(out, hue / 12, alpha);