Add support for grayscale modes

README.md

@@ -99,7 +99,14 @@ let desaturatedColor = originalColor.desaturated()
 // equivalent to
 // desaturatedColor = originalColor.desaturated(amount: 0.2)
 
+// equivalent to
+// let grayscaledColor = originalColor.grayscaled(mode: .luminance)
 let grayscaledColor = originalColor.grayscaled()
+
+let grayscaledColorLuminance = originalColor.grayscaled(mode: .luminance)
+let grayscaledColorLightness = originalColor.grayscaled(mode: .lightness)
+let grayscaledColorAverage = originalColor.grayscaled(mode: .average)
+let grayscaledColorValue = originalColor.grayscaled(mode: .value)
 ```
 
 #### Adjust-hue & Complement

Sources/DynamicColor+Deriving.swift

@@ -99,13 +99,25 @@ public extension DynamicColor {
   /**
    Creates and returns a color object converted to grayscale.
 
-   This is identical to desaturateColor(1).
-
    - returns: A grayscale DynamicColor.
-   - seealso: desaturateColor:
+   - seealso: desaturated:
    */
-  final func grayscaled() -> DynamicColor {
+  final func grayscaled(mode: GrayscalingMode = .lightness) -> DynamicColor {
-    return desaturated(amount: 1)
+    let (r, g, b, a) = self.toRGBAComponents()
+
+    let l: CGFloat
+    switch mode {
+    case .luminance:
+      l = (0.299 * r) + (0.587 * g) + (0.114 * b)
+    case .lightness:
+      l = 0.5 * (max(r, g, b) + min(r, g, b))
+    case .average:
+      l = (1.0 / 3.0) * (r + g + b)
+    case .value:
+      l = max(r, g, b)
+    }
+
+    return HSL(hue: 0.0, saturation: 0.0, lightness: l, alpha: a).toDynamicColor()
   }
 
   /**

Sources/Utils.swift

@@ -71,3 +71,19 @@ internal func roundToHex(_ x: CGFloat) -> UInt32 {
   
   return UInt32(rounded)
 }
+
+/**
+ Defines the mode (i.e color space) used for grayscaling.
+
+ [More info](https://en.wikipedia.org/wiki/Lightness#Lightness_and_human_perception)
+*/
+public enum GrayscalingMode {
+    /// XYZ luminance
+    case luminance
+    /// HSL lightness
+    case lightness
+    /// RGB average
+    case average
+    /// HSV value
+    case value
+}

Tests/DynamicColorTests.swift

@@ -289,7 +289,6 @@ class DynamicColorTests: XCTestCase {
   func testGrayscaleColor() {
     let grayscale   = DynamicColor(hex: 0xc0392b).grayscaled()
     let desaturated = DynamicColor(hex: 0xc0392b).desaturated(amount: 1)
-
     XCTAssert(grayscale.isEqual(desaturated), "Colors should be the same")
   }