Unity3D UGUI:圆形Image组件,可用来制作头像

昨天在改项目的时候,看到人物头像是圆形的，我就想到用UGUI的Mask组件，但是我试了一下，效果不是很好,而且性能上也不是很理想，所以我就找到一个比较好的解决办法，之前也考虑过用Image上的Material去弄，但是也不是很完美，后来看到一篇文章，说是重写Image组件，所以就有了下面我要提到的东西(只支持5.3版本以上)。

首先需要重写Image，由于继承UnityEngine基类的派生类不能在Inspector里显示自定义参数。所以我们要新建BaseImage类来代替Image类。原Image源码有近千行代码，BaseImage对其进行了部分精简，只支持Simple Image Type，并去掉了eventAlphaThreshold的相关代码。经过删减，得到一个百行代码的BaseImage类，精简版Image就完成了。

using System;
using UnityEngine;
using System.Collections;
using UnityEngine.Serialization;
using UnityEngine.UI;

public class BaseImage : MaskableGraphic,ISerializationCallbackReceiver, ILayoutElement, ICanvasRaycastFilter
{

    // Use this for initialization
    void Start () {
    
    }
    
    // Update is called once per frame
    void Update () {
    
    }

    [FormerlySerializedAs("m_Frame")]
    [SerializeField]
    private Sprite m_Sprite;
    public Sprite sprite { get { return m_Sprite; } set { if (SetPropertyUtilityExt.SetClass(ref m_Sprite, value)) SetAllDirty(); } }

    [NonSerialized]
    private Sprite m_OverrideSprite;
    public Sprite overrideSprite { get { return m_OverrideSprite == null ? sprite : m_OverrideSprite; } set { if (SetPropertyUtilityExt.SetClass(ref m_OverrideSprite, value)) SetAllDirty(); } }


    /// 

    /// Image's texture comes from the UnityEngine.Image.
    /// 
    public override Texture mainTexture
    {
        get
        {
            return overrideSprite == null ? s_WhiteTexture : overrideSprite.texture;
        }
    }

    public float pixelsPerUnit
    {
        get
        {
            float spritePixelsPerUnit = 100;
            if (sprite)
                spritePixelsPerUnit = sprite.pixelsPerUnit;

            float referencePixelsPerUnit = 100;
            if (canvas)
                referencePixelsPerUnit = canvas.referencePixelsPerUnit;

            return spritePixelsPerUnit / referencePixelsPerUnit;
        }
    }

    /// 

    /// 子类需要重写该方法来自定义Image形状
    /// 
    /// 
    protected override void OnPopulateMesh(VertexHelper vh)
    {
        base.OnPopulateMesh(vh);
    }

    #region ISerializationCallbackReceiver
    public void OnAfterDeserialize()
    {
    }

    //
    // 摘要: 
    //     Implement th