Text文件颜色渐变

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

[AddComponentMenu("UI/Effects/Gradient")]
[RequireComponent(typeof(Text))]
public class Gradient : BaseMeshEffect
{
public Color colorTop = Color.white;
public Color colorCenter = Color.grey;
public Color colorBottom = Color.black;

public bool MultiplyTextColor = false;

public static Color32 Multiply(Color32 a, Color32 b)
{
a.r = (byte)((a.r * b.r) >> 8);
a.g = (byte)((a.g * b.g) >> 8);
a.b = (byte)((a.b * b.b) >> 8);
a.a = (byte)((a.a * b.a) >> 8);
return a;
}

private void ModifyVertices(VertexHelper vh)
{
List<UIVertex> verts = new List<UIVertex>(vh.currentVertCount);
vh.GetUIVertexStream(verts);
vh.Clear();

int step = 6;

for (int i = 0; i < verts.Count; i += step)
{
//6 point
var tl = multiplyColor(verts[i + 0], colorTop);
var tr = multiplyColor(verts[i + 1], colorTop);
var bl = multiplyColor(verts[i + 4], colorBottom);
var br = multiplyColor(verts[i + 3], colorBottom);
var cl = calcCenterVertex(verts[i + 0], verts[i + 4]);
var cr = calcCenterVertex(verts[i + 1], verts[i + 2]);

vh.AddVert(tl);
vh.AddVert(tr);
vh.AddVert(cr);
vh.AddVert(cr);
vh.AddVert(cl);
vh.AddVert(tl);

vh.AddVert(cl);
vh.AddVert(cr);
vh.AddVert(br);
vh.AddVert(br);
vh.AddVert(bl);
vh.AddVert(cl);
}

for (int i = 0; i < vh.currentVertCount; i += 12)
{
vh.AddTriangle(i + 0, i + 1, i + 2);
vh.AddTriangle(i + 3, i + 4, i + 5);
vh.AddTriangle(i + 6, i + 7, i + 8);
vh.AddTriangle(i + 9, i + 10, i + 11);
}
}

private UIVertex multiplyColor(UIVertex vertex, Color color)
{
if (MultiplyTextColor)
vertex.color = Multiply(vertex.color, color);
else
vertex.color = color;
return vertex;
}

private UIVertex calcCenterVertex(UIVertex top, UIVertex bottom)
{
UIVertex center;
center.normal = (top.normal + bottom.normal) / 2;
center.position = (top.position + bottom.position) / 2;
center.tangent = (top.tangent + bottom.tangent) / 2;
center.uv0 = (top.uv0 + bottom.uv0) / 2;
center.uv1 = (top.uv1 + bottom.uv1) / 2;

if (MultiplyTextColor)
{
//multiply color
var color = Color.Lerp(top.color, bottom.color, 0.5f);
center.color = Multiply(color, colorCenter);
}
else
{
center.color = colorCenter;
}

return center;
}

#region implemented abstract members of BaseMeshEffect

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

ModifyVertices(vh);
}

#endregion
}