Unity UI/字体颜色渐变效果实现

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;


/// <summary>
/// 渐变
/// </summary>
[DisallowMultipleComponent]
[AddComponentMenu("UI/Effects/UIGradient")]
public class UIGradient : BaseMeshEffect
{
    protected UIGradient()
    {

    }

    /// <summary>
    /// 渐变方向
    /// </summary>
    public enum EGradientDir
    {
        TopToBottom,
        BottomToTop,
        LeftToRight,
        RightToLeft,
    }

    /// <summary>
    /// 渐变方向
    /// </summary>
    [SerializeField]
    EGradientDir m_GradientDir = EGradientDir.TopToBottom;
    public EGradientDir GradientDir
    {
        get
        {
            return m_GradientDir;
        }
        set
        {
            m_GradientDir = value;
            graphic.SetVerticesDirty();
        }
    }

    //颜色数组
    [SerializeField]
    Color32[] m_ColorArray = new Color32[2] { Color.black, Color.white };
    public Color32[] ColorArray
    {
        get
        {
            return m_ColorArray;
        }
        set
        {
            m_ColorArray = value;
            graphic.SetVerticesDirty();
        }
    }

    //顶点缓存
    List<UIVertex> m_VertexCache = new List<UIVertex>();
    //绘制使用的顶点列表
    List<UIVertex> m_VertexList = new List<UIVertex>();

    public override void ModifyMesh(VertexHelper vh)
    {
        if (!IsActive())
        {
            return;
        }

        vh.GetUIVertexStream(m_VertexCache);

        switch (m_GradientDir)
        {
            case EGradientDir.TopToBottom:
                ApplyGradient_TopToBottom(m_VertexCache);
                break;
            case EGradientDir.BottomToTop:
                ApplyGradient_BottomToTop(m_VertexCache);
                break;
            case EGradientDir.LeftToRight:
                ApplyGradient_LeftToRight(m_VertexCache);
                break;
            case EGradientDir.RightToLeft:
                ApplyGradient_RightToLeft(m_VertexCache);
                break;
            default:
                break;
        }

        vh.Clear();
        vh.AddUIVertexTriangleStream(m_VertexList);
        m_VertexCache.Clear();
        m_VertexList.Clear();
    }

    void ApplyGradient_TopToBottom(List<UIVertex> vertexCache)
    {
        if (vertexCache.Count == 0)
        {
            return;
        }
        if (m_ColorArray.Length < 2)
        {
            return;
        }

        int vertexCountP