     }
 }
 
-private var _autoCIContext    = UIImage._AutomaticCIContext()
-private var _metalCIContext   = UIImage._MetalBasedCIContext()
-private var _openGLESCIContex = UIImage._OpenGLESBasedCIContext()
+private var _autoCIContext     = UIImage._AutomaticCIContext()
+private var _metalCIContext    = UIImage._MetalBasedCIContext()
+private var _openGLESCIContext = UIImage._OpenGLESBasedCIContext()
 
 /// Get the context of core image with the given render destination.
 private func _ciContext(of dest: UIImage.RenderDestination) -> CIContext! {

        case .metal:
            return _metalCIContext.context
        case .openGLES:
            return _openGLESCIContex.context
        }
    default: return nil
    }

    public enum RenderDestination {
        /// A type representing the GPU-Based rendering.
        public enum GPU {
            /// Indicates the rendering is based on a `MTLDevice`. The GPU-Based contex for this value
            /// will automatic fallthrough to the OpenGL ES-Based if the Metal device is not available.
            case metal
            /// Indicates the rendering is based on the api of `OpenGL ES`.
            case openGLES
