This project is a case study trying to Replicate the default Gradient Inspector from Unity3D, but changing few aspects:

• Removing the limit of 8 color/alpha keys:
• Adding the possibility to sample the color/alpha value over the gradient as seen in Adobe Photoshop:
• Adding optional GradientRepeatMode field to Evaluate method:
  • Clamp: Default gradient Behaviour
  • PingPong: Pingpongs the time value from 0 to 1
  • Repeat: Repeats the value between 0 and 1

The usage is the same from UnityEngine.Gradient. with the same methods and parameters. Just declare the property as GradientField instead of Gradient:

   [Header("UnityEngine.Gradient")]
   public Gradient gradient;

   [Header("GradientField")]
   public GradientField gradientField;

   void Start()
   {
      //Works!
      gradientField.colorKeys = gradient.colorKeys;
      gradientField.alphaKeys = gradient.alphaKeys;
   }

   void Update()
   {
      //Also works!
      Color result = gradientField.Evaluate(Time.time);

      Color otherResult = gradientField.Evaluate(Time.time, GradientRepeatMode.PingPong);
   }

Inspector:

This solution is built trying to replicate the Unity Behaviour but performance was not taken in consideration. If you are trying to use A LOT color/alpha keys, consideer implementing a better search algorythim.