Gradient.cs

using System.Collections.Generic;

/// <summary>
/// Modified Gradient effect script from http://answers.unity3d.com/questions/1086415/gradient-text-in-unity-522-basevertexeffect-is-obs.html
/// -Uses Unity's Gradient class to define the color
/// -Offset is now limited to -1,1
/// -Multiple color blend modes
///
/// Remember that the colors are applied per-vertex so if you have multiple points on your gradient where the color changes and there aren't enough vertices, you won't see all of the colors.
/// </summary>
namespace UnityEngine.UI {
    [AddComponentMenu("UI/Effects/Gradient")]
    public class Gradient : BaseMeshEffect {
        [SerializeField]
        Type _gradientType;

        [SerializeField]
        Blend _blendMode = Blend.Multiply;

        [SerializeField]
        [Range(-1, 1)]
        float _offset = 0f;

        [SerializeField]
        UnityEngine.Gradient _effectGradient = new UnityEngine.Gradient() { colorKeys = new GradientColorKey[] { new GradientColorKey(Color.black, 0), new GradientColorKey(Color.white, 1) } };

        #region Properties
        public Blend BlendMode {
            get { return _blendMode; }
            set { _blendMode = value; }
        }

        public UnityEngine.Gradient EffectGradient {
            get { return _effectGradient; }
            set { _effectGradient = value; }
        }

        public Type GradientType {
            get { return _gradientType; }
            set { _gradientType = value; }
        }

        public float Offset {
            get { return _offset; }
            set { _offset = value; }
        }
        #endregion

        public override void ModifyMesh(VertexHelper helper) {
            if(!IsActive() || helper.currentVertCount == 0)
                return;

            List<UIVertex> _vertexList = new List<UIVertex>();

            helper.GetUIVertexStream(_vertexList);

            int nCount = _vertexList.Count;
            switch(GradientType) {
                case Type.Horizontal: {
                        float left = _vertexList[0].position.x;
                        float right = _vertexList[0].position.x;
                        float x = 0f;

                        for(int i = nCount - 1; i >= 1; --i) {
                            x = _vertexList[i].position.x;

                            if(x > right) right = x;
                            else if(x < left) left = x;
                        }

                        float width = 1f / (right - left);
                        UIVertex vertex = new UIVertex();

                        for(int i = 0; i < helper.currentVertCount; i++) {
                            helper.PopulateUIVertex(ref vertex, i);

                            vertex.color = BlendColor(vertex.color, EffectGradient.Evaluate((vertex.position.x - left) * width - Offset));

                            helper.SetUIVertex(vertex, i);
                        }
                    }
                    break;

                case Type.Vertical: {
                        float bottom = _vertexList[0].position.y;
                        float top = _vertexList[0].position.y;
                        float y = 0f;

                        for(int i = nCount - 1; i >= 1; --i) {
                            y = _vertexList[i].position.y;

                            if(y > top) top = y;
                            else if(y < bottom) bottom = y;
                        }

                        float height = 1f / (top - bottom);
                        UIVertex vertex = new UIVertex();

                        for(int i = 0; i < helper.currentVertCount; i++) {
                            helper.PopulateUIVertex(ref vertex, i);

                            vertex.color = BlendColor(vertex.color, EffectGradient.Evaluate((vertex.position.y - bottom) * height - Offset));

                            helper.SetUIVertex(vertex, i);
                        }
                    }
                    break;
            }
        }

        Color BlendColor(Color colorA, Color colorB) {
            switch(BlendMode) {
                default: return colorB;
                case Blend.Add: return colorA + colorB;
                case Blend.Multiply: return colorA * colorB;
            }
        }

        public enum Type {
            Horizontal,
            Vertical
        }

        public enum Blend {
            Override,
            Add,
            Multiply
        }
    }
}