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 this method to receive a callback after unity serialized your object.
    public void OnBeforeSerialize()
    {
    }
    #endregion

    #region ILayoutElement
    public virtual void CalculateLayoutInputHorizontal() { }
    public virtual void CalculateLayoutInputVertical() { }

    public virtual float minWidth { get { return 0; } }

    public virtual float preferredWidth
    {
        get
        {
            if (overrideSprite == null)
                return 0;
            return overrideSprite.rect.size.x / pixelsPerUnit;
        }
    }

    public virtual float flexibleWidth { get { return -1; } }

    public virtual float minHeight { get { return 0; } }

    public virtual float preferredHeight
    {
        get
        {
            if (overrideSprite == null)
                return 0;
            return overrideSprite.rect.size.y / pixelsPerUnit;
        }
    }

    public virtual float flexibleHeight { get { return -1; } }

    public virtual int layoutPriority { get { return 0; } }
    #endregion

    #region ICanvasRaycastFilter
    public virtual bool IsRaycastLocationValid(Vector2 screenPoint, Camera eventCamera)
    {
        return true;
    }
    #endregion

}

然后,开始写CricleImage类，Image类继承自MaskableGraphic，实现了ISerializationCallbackReceiver, ILayoutElement, ICanvasRaycastFilter这三个接口。最关键的是MaskableGraphic类，MaskableGraphic负责绘制逻辑，MaskableGraphic继承自Graphic，Graphic里有个OnPopulateMesh函数，这正是我们需要的函数。

UI元素生成顶点数据时会调用OnPopulateMesh(VertexHelper vh)函数，我们只要继承改写OnPopulateMesh函数，将原先的矩形顶点数据清除，改写入圆形顶点数据，这样渲染出来的自然是圆形图片。

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

[AddComponentMenu("UI/Circle Image")]
public class CircleImage : BaseImage
{

    // Use this for initialization
    void Awake()
    {
        innerVertices = new List();
        outterVertices = new List();
    }

    // Update is called once per frame
    void Update()
    {
        this.thickness = (float)Mathf.Clamp(this.thickness, 0, rectTransform.rect.width / 2);
    }

    [Tooltip("圆形或扇形填充比例")]
    [Range(0, 1)]
    public float fillPercent = 1f;
    [Tooltip("是否填充圆形")]
    public bool fill = true;
    [Tooltip("圆环宽度")]
    public float thickness = 5;
    [Tooltip("圆形")]
    [Range(3, 100)]
    public int segements = 20;

    private List innerVertices;
    private List outterVertices;

    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear();

        innerVertices.Clear();
        outterVertices.Clear();

        float degreeDelta = (float)(2 * Mathf.PI / segements);
        int curSegements = (int)(segements * fillPercent);

        float tw = rectTransform.rect.width;
        float th = rectTransform.rect.height;
        float outerRadius = rectTransform.pivot.x * tw;
        float innerRadius = rectTransform.pivot.x * tw - thickness;

        Vector4 uv = overrideSprite != null ? DataUtility.GetOuterUV(overrideSprite) : Vector4.zero;

        float uvCenterX = (uv.x + uv.z) * 0.5f;
        float uvCenterY = (uv.y + uv.w) * 0.5f;
        float uvScaleX = (uv.z - uv.x) / tw;
        float uvScaleY = (uv.w - uv.y) / th;

        float curDegree = 0;
        UIVertex uiVertex;
        int verticeCount;
        int triangleCount;
        Vector2 curVertice;

        if (fill) //圆形
        {
            curVertice = Vector2.zero;
            verticeCount = curSegements + 1;
            uiVertex = new UIVertex();
            uiVertex.color = color;
            uiVertex.position = curVertice;
            uiVertex.uv0 = new Vector2(curVertice.x * uvScaleX + uvCenterX, curVertice.y * uvScaleY + uvCenterY);
            vh.AddVert(uiVertex);

            for (int i = 1; i < verticeCount; i++)
            {
                float cosA = Mathf.Cos(curDegree);
                float sinA = Mathf.Sin(curDegree);
                curVertice = new Vector2(cosA * outerRadius, sinA * outerRadius);
                curDegree += degreeDelta;

                uiVertex = new UIVertex();
                uiVertex.color = color;
                uiVertex.position = curVertice;
                uiVertex.uv0 = new Vector2(curVertice.x * uvScaleX + uvCenterX, curVertice.y * uvScaleY + uvCenterY);
                vh.AddVert(uiVertex);

                outterVertices.Add(curVertice);
            }

            triangleCount = curSegements * 3;
            for (int i = 0, vIdx = 1; i < triangleCount - 3; i += 3, vIdx++)
            {
                vh.AddTriangle(vIdx, 0, vIdx + 1);
            }
            if (fillPercent == 1)
            {
                //首尾顶点相连
                vh.AddTriangle(verticeCount - 1, 0, 1);
            }
        }
        else//圆环
        {
            verticeCount = curSegements * 2;
            for (int i = 0; i < verticeCount; i += 2)
            {
                float cosA = Mathf.Cos(curDegree);
                float sinA = Mathf.Sin(curDegree);
                curDegree += degreeDelta;

                curVertice = new Vector3(cosA * innerRadius, sinA * innerRadius);
                uiVertex = new UIVertex();
                uiVertex.color = color;
                uiVertex.position = curVertice;
                uiVertex.uv0 = new Vector2(curVertice.x * uvScaleX + uvCenterX, curVertice.y * uvScaleY + uvCenterY);
                vh.AddVert(uiVertex);
                innerVertices.Add(curVertice);

                curVertice = new Vector3(cosA * outerRadius, sinA * outerRadius);
                uiVertex = new UIVertex();
                uiVertex.color = color;
                uiVertex.position = curVertice;
                uiVertex.uv0 = new Vector2(curVertice.x * uvScaleX + uvCenterX, curVertice.y * uvScaleY + uvCenterY);
                vh.AddVert(uiVertex);
                outterVertices.Add(curVertice);
            }

            triangleCount = curSegements * 3 * 2;
            for (int i = 0, vIdx = 0; i < triangleCount - 6; i += 6, vIdx += 2)
            {
                vh.AddTriangle(vIdx + 1, vIdx, vIdx + 3);
                vh.AddTriangle(vIdx, vIdx + 2, vIdx + 3);
            }
            if (fillPercent == 1)
            {
                //首尾顶点相连
                vh.AddTriangle(verticeCount - 1, verticeCount - 2, 1);
                vh.AddTriangle(verticeCount - 2, 0, 1);
            }
        }

    }

    public override bool IsRaycastLocationValid(Vector2 screenPoint, Camera eventCamera)
    {
        Sprite sprite = overrideSprite;
        if (sprite == null)
            return true;

        Vector2 local;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(rectTransform, screenPoint, eventCamera, out local);
        return Contains(local, outterVertices, innerVertices);
    }

    private bool Contains(Vector2 p, List outterVertices, List innerVertices)
    {
        var crossNumber = 0;
        RayCrossing(p, innerVertices, ref crossNumber);//检测内环
        RayCrossing(p, outterVertices, ref crossNumber);//检测外环
        return (crossNumber & 1) == 1;
    }

    /// 

    /// 使用RayCrossing算法判断点击点是否在封闭多边形里
    /// 
    /// 
    /// 
    /// 
    private void RayCrossing(Vector2 p, List vertices, ref int crossNumber)
    {
        for (int i = 0, count = vertices.Count; i < count; i++)
        {
            var v1 = vertices[i];
            var v2 = vertices[(i + 1) % count];

            //点击点水平线必须与两顶点线段相交
            if (((v1.y <= p.y) && (v2.y > p.y))
                || ((v1.y > p.y) && (v2.y <= p.y)))
            {
                //只考虑点击点右侧方向，点击点水平线与线段相交，且交点x > 点击点x，则crossNumber+1
                if (p.x < v1.x + (p.y - v1.y) / (v2.y - v1.y) * (v2.x - v1.x))
                {
                    crossNumber += 1;
                }
            }
        }
    }


}

最后,还有一个辅助类

using UnityEngine;

internal static class SetPropertyUtilityExt
{
    public static bool SetColor(ref Color32 currentValue, Color32 newValue)
    {
        if (currentValue.r == newValue.r && currentValue.g == newValue.g && currentValue.b == newValue.b && currentValue.a == newValue.a)
            return false;

        currentValue = newValue;
        return true;
    }

    public static bool SetStruct(ref T currentValue, T newValue) where T : struct
    {
        if (currentValue.Equals(newValue))
            return false;

        currentValue = newValue;
        return true;
    }

    public static bool SetClass(ref T currentValue, T newValue) where T : class
    {
        if ((currentValue == null && newValue == null) || (currentValue != null && currentValue.Equals(newValue)))
            return false;

        currentValue = newValue;
        return true;
    }
}

上面就是所有代码了，上面还加入了圆形区域的点击检测，是通过Ray-Crossing算法判断的，也就是由这个点发射一条射线与多边形相交，如果交点是奇数，说明在多边形内，如果是偶数个就是在多边形外面。下面是package包，有需要的去下载吧。
下载链接: http://pan.baidu.com/s/1nvhqBLv 密码: qa1p