         case entropy = "entropy"
     }
 
+    // MARK: - Properties
+
+    var storage = [ImageOptionKey: Any]()
+
     // MARK: - Adjustment Properties
 
     /**
      Adjusts the brightness of the image.
-    
+
      Values are clamped to the range `-100...100`.
 
      - seealso:
      [Imgix API Reference](https://www.imgix.com/docs/reference/adjustment#param-bri)
     */
     public var brightness: Int? {
-        get { return _brightness }
-        set { _brightness = newValue?.clamped(to: -100...100) }
-    }
-    private var _brightness: Int?
+        get { return storage[.brightness] as? Int }
+        set { storage[.brightness] = newValue?.clamped(to: -100...100) }
+    }
 
     /**
      Adjusts the contrast of the image.

     - seealso:
     [Imgix API Reference](https://www.imgix.com/docs/reference/format#param-fm)
    */
    public var format: Format?

    /**
     The DPI value in the Exif header of the resulting image.

     [Imgix API Reference](https://www.imgix.com/docs/reference/adjustment#param-high)
    */
    public var highlight: Int? {
        get { return storage[.highlight] as? Int }
        set { storage[.highlight] = newValue?.clamped(to: -100...100) }
    }

    /**
     Changes the overall hue, or tint, of the source pixels.
