text: /*****************************************************************************/
  // Copyright 2006-2019 Adobe Systems Incorporated
  // All Rights Reserved.
  //
  // NOTICE:  Adobe permits you to use, modify, and distribute this file in
  // accordance with the terms of the Adobe license agreement accompanying it.
  /*****************************************************************************/
  
  /** \file
   * Classes for a 1D floating-point to floating-point function abstraction.
   */
  
  /*****************************************************************************/
  
  #ifndef __dng_1d_function__
  #define __dng_1d_function__
  
  /*****************************************************************************/
  
  #include "dng_classes.h"
  #include "dng_types.h"
  
  /*****************************************************************************/
  
  /// \brief A 1D floating-point function.
  ///
  /// The domain (input) is always from 0.0 to 1.0, while the range (output) can be an arbitrary interval.
  
  class dng_1d_function
  	{
  
  	public:
  
  		virtual ~dng_1d_function ();
  
  		/// Returns true if this function is the map x -> y such that x == y for all x . That is if Evaluate(x) == x for all x.
  
  		virtual bool IsIdentity () const;
  
  		/// Return the mapping for value x.
  		/// This method must be implemented by a derived class of dng_1d_function and the derived class determines the
  		/// lookup method and function used.
  		/// \param x A value between 0.0 and 1.0 (inclusive).
  		/// \retval Mapped value for x
  
  		virtual real64 Evaluate (real64 x) const = 0;
  
  		/// Return the reverse mapped value for y.
  		/// This method can be implemented by derived classes. The default implementation uses Newton's method to solve
  		/// for x such that Evaluate(x) == y.
  		/// \param y A value to reverse map. Should be within the range of the function implemented by this dng_1d_function .
  		/// \retval A value x such that Evaluate(x) == y (to very close approximation).
  
  		virtual real64 EvaluateInverse (real64 y) const;
  
  	};
  
  /*****************************************************************************/
  
  /// An identity (x -> y such that x == y for all x) mapping function.
  
  class dng_1d_identity: public dng_1d_function
  	{
  
  	public:
  		/// Always returns true for this class.
  
  		virtual bool IsIdentity () const;
  
  		/// Always returns x for this class.
  
  		virtual real64 Evaluate (real64 x) const;
  
  		/// Always returns y for this class.
  
  		virtual real64 EvaluateInverse (real64 y) const;
  
  		/// This class is a singleton, and is entirely threadsafe. Use this method to get an instance of the class.
  
  		static const dng_1d_function & Get ();
  
  	};
  
  /*****************************************************************************/
  
  /// A dng_1d_function that represents the composition (curry) of two other dng_1d_functions.
  
  class dng_1d_concatenate: public dng_1d_function
  	{
  
  	protected:
  
  		const dng_1d_function &fFunction1;
  
  		const dng_1d_function &fFunction2;
  
  	public:
  
  		/// Create a dng_1d_function which computes y = function2.Evaluate(function1.Evaluate(x)).
  		/// Compose function1 and function2 to compute y = function2.Evaluate(function1.Evaluate(x)). The range of function1.Evaluate must be a subset of 0.0 to 1.0 inclusive,
  		/// otherwise the result of function1(x) will be pinned (clipped) to 0.0 if <0.0 and to 1.0 if > 1.0 .
  		/// \param function1 Inner function of composition.
  		/// \param function2 Outer function of composition.
  
  		dng_1d_concatenate (const dng_1d_function &function1,
  							const dng_1d_function &function2);
  
  		/// Only true if both function1 and function2 have IsIdentity equal to true.
  
  		virtual bool IsIdentity () const;
  
  		/// Return the composed mapping for value x.
  		/// \param x A value between 0.0 and 1.0 (inclusive).
  		/// \retval function2.Evaluate(function1.Evaluate(x)).
  
  		virtual real64 Evaluate (real64 x) const;
  
  		/// Return the reverse mapped value for y.
  		/// Be careful using this method with compositions where the inner function does not have a range 0.0 to 1.0 . (Or better yet, do not use such functions.)
  		/// \param y A value to reverse map. Should be within the range of function2.Evaluate.
  		/// \retval A value x such that function2.Evaluate(function1.Evaluate(x)) == y (to very close approximation).
  
  		virtual real64 EvaluateInverse (real64 y) const;
  
  	};
  
  /*****************************************************************************/
  
  /// A dng_1d_function that represents the inverse of another dng_1d_function.
  
  class dng_1d_inverse: public dng_1d_function
  	{
  
  	protected:
  
  		const dng_1d_function &fFunction;
  
  	public:
  
  		dng_1d_inverse (const dng_1d_function &f);
  
  		virtual bool IsIdentity () const;
  
  		virtual real64 Evaluate (real64 x) const;
  
  		virtual real64 EvaluateInverse (real64 y) const;
  
  	};
  
  /*****************************************************************************/
  
  #endif
  
  /*****************************************************************************/
  