Unity Image - 镜像

1、为什么要使用镜像

在游戏开发过程中,我们经常会为了节省 美术图片资源大小,美术会将两边相同的图片进行切一半来处理。如下所示一个按钮 需要 400 * 236,然而美术只需要切一张 74*236的大小就可以了。这样一来图集就可以容纳更多的图片。内存占用也更少。

Unity Image - 镜像_第1张图片Unity Image - 镜像_第2张图片

2.实现方案

  1. 拷贝一张图片,然后把 scale改成-1,这种方法比较笨,需要多加一张图片,操作起来也很不方便。没啥好讲的。
  2. 拷贝原有的图片顶点,进行对称处理。如下图所示。

Unity Image - 镜像_第3张图片

3.在哪里拿到mesh顶点?修改顶点?

BaseMeshEffect :是用于实现网格效果的抽象类实现IMeshModifier接口,是Shadow、Outline等效果的基类。
从Unity uGUI原理解析-Graphic可以知道,Graphic 在执行 DoMeshGeneration 时会获取到当前GameObject上的所有实现 IMeshModifier 的组件。 并且会调用 ModifyMesh 方法来修改当前Graphic 的Mesh数据。BaseMeshEffect 的类结构图如下:

Unity Image - 镜像_第4张图片

我们编写一个MirrorImage来继承BaseMeshEffect,拿到 VertexHelper,获取网格的顶点流数据,然后进行下面的镜像,映射操作:

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

public enum MirrorType
{
    Horizontal,
    Vertical,
    HorizontalAndVertical
}

[RequireComponent(typeof(Image))]
public class MirrorImage : BaseMeshEffect
{
    public MirrorType mirrorType = MirrorType.Horizontal;

    public Dictionary MirrorDic = new Dictionary()
    {
        {Image.Type.Simple, new SimpleMirror()},
        {Image.Type.Sliced, new SlicedMirror()},
        {Image.Type.Tiled, new TiledMirror()},
        {Image.Type.Filled, new FilledMirror()},
    };

    public Image image => graphic as Image;

    public override void ModifyMesh(VertexHelper vh)
    {
        if (!IsActive()) return;
        Image.Type imageType = (graphic as Image).type;
        List vertices = new List();
        vh.GetUIVertexStream(vertices);
        vh.Clear();
        
        MirrorDic[imageType].Draw(image, vertices, mirrorType);
        vh.AddUIVertexTriangleStream(vertices);
    }

    [Button("Set Native Size")]
    public void SetNativeSize()
    {
        if (image.sprite != null)
        {
            float w = image.sprite.rect.width / image.pixelsPerUnit;
            float h = image.sprite.rect.height / image.pixelsPerUnit;
            image.rectTransform.anchorMax = image.rectTransform.anchorMin;
            float x = mirrorType == MirrorType.Horizontal || mirrorType == MirrorType.HorizontalAndVertical ? 2 : 1;
            float y = mirrorType == MirrorType.Vertical || mirrorType == MirrorType.HorizontalAndVertical ? 2 : 1;
            image.rectTransform.sizeDelta = new Vector2(w * x, h * y);
            image.SetAllDirty();
        }
    }
}

当然除了继承BaseMeshEffect,当然还可以直接继承Image,重写OnPopulateMesh。

4.如何实现顶点的镜像?

很简单 假设中心的是 center( 0,0),需要水平镜像的点 A(-1,0) 镜像后的点就是 B(-1,0)需要满足   A 到Center的距离 == B到center的距离:

所以我们先求出镜像的中心点 center的位置 ,因为矩形有自己的中心点位置,我们需要求出镜像的中心点位置在改矩形下的坐标,这么说可能有点绕看下图:

矩形的宽w:100,h:100,矩形自身的中心点(蓝色的圈) 这边为称为O点,在Unity中是以  Rect中的 x,y代表的是坐下角的点 既 (-75,-50),

对于Rect(x,y) 不理解的话可以看下GPT的回答,可能比我讲的清楚:

Unity Image - 镜像_第5张图片

那么镜像真正的中心点坐标

  • center.x = rect.x + rect.width;
  • center.y = rect.y + rect.height;

那么要镜像的点 A 镜像后为B   ,需要求出A到center的长度大小然后取反 + 矩形中心点与镜像中心点的偏移

B.x = -(A.x - center.x) + (rect.x+rect.width/2)

B.y = -(A.y - center.y) + (rect.x+rect.width/2)

Unity Image - 镜像_第6张图片

逻辑分析完了,直接看代码吧:


using System.Collections.Generic;
using UnityEngine;

public static class MirrorUtlis
{
    public static void Mirror(Rect rect,List uiVertices,MirrorType type)
    {
        int count = uiVertices.Count;
        switch (type)
        {
            case MirrorType.Horizontal:
                Mirror(rect, uiVertices, type, count);
                break;
            case MirrorType.Vertical:
                Mirror(rect, uiVertices, type, count);
                break;
            case MirrorType.HorizontalAndVertical:
                Mirror(rect, uiVertices, MirrorType.Horizontal, count);
                Mirror(rect, uiVertices, MirrorType.Vertical, 2 * count);
                break;
        }
        RemoveVertices(uiVertices);
    }

    private static void Mirror(Rect rect, List uiVertices, MirrorType type, int count)
    {
        for (int i = 0; i < count; i++)
        {
            UIVertex vertex = uiVertices[i];
            switch (type)
            {
                case MirrorType.Horizontal:
                    vertex = HorizontalMirror(rect, vertex);
                    break;
                case MirrorType.Vertical:
                    vertex = VerticalMirror(rect, vertex);
                    break;
                case MirrorType.HorizontalAndVertical:
                    vertex = HorizontalMirror(rect, vertex);
                    vertex = VerticalMirror(rect, vertex);
                    break;
            }
            uiVertices.Add(vertex);
        }
    }

    private static UIVertex HorizontalMirror(Rect rect, UIVertex vertex)
    {
        float center = rect.width / 2 + rect.x;
        vertex.position.x = -(vertex.position.x - center) + rect.x + rect.width/2;
        return vertex;
    }
    
    private static UIVertex VerticalMirror(Rect rect, UIVertex vertex)
    {
        float center = rect.height / 2 + rect.y;
        vertex.position.y = -(vertex.position.y - center) + rect.y + rect.height/2;
        return vertex;
    }
    
    // 移除构不成三角形的顶点
    private static void RemoveVertices(List uiVertices)
    {
        int end = uiVertices.Count;

        for (int i = 2; i < end; i += 3)
        {
            UIVertex v1 = uiVertices[i];
            UIVertex v2 = uiVertices[i - 1];
            UIVertex v3 = uiVertices[i - 2];

            if (v1.position == v2.position ||
                v1.position == v3.position ||
                v2.position == v3.position)
            {
                // 移动到尾部
                ChaneVertices(uiVertices, i - 1, end - 3);
                ChaneVertices(uiVertices, i - 2, end - 2);
                ChaneVertices(uiVertices, i, end - 1);
                end -= 3;
            }
        }
        
        if(end < uiVertices.Count)
            uiVertices.RemoveRange(end,uiVertices.Count - end);
    }
    
    private static void ChaneVertices(List uiVertices,int a,int b)
    {
        (uiVertices[a], uiVertices[b]) = (uiVertices[b], uiVertices[a]);
    }
}

在顶点镜像前我们需要对顶点进行顶点映射,什么时时映射?

Unity Image - 镜像_第7张图片

如上图所示,原来图片是白色区域大小,顶点为白色图片的四个顶点,因为要做对称,所以需要留出一半的位置来增加映射后的顶点。

在不同模式下的顶点映射需要做不同处理,在Unity中有一下几种模式:

  • Simple: 如上面的图所示,对顶点的位置 除以 2 即可比较简单
  • Sliced:九宫格模式下因为要保留九宫格的顶点位置,不能让九宫格保留的位置发生形变,就不能直接除以2来处理,需要做平移处理。具体实现下面在讲
  • Filed:平铺模式下是不需要在镜像网格顶点的,因为平铺下的图片顶点是已经增加好的了,我们只需要对UV做镜像就可以了
  • Filled:暂时未实现该模式下的,以后有时间在研究。

由于有多种模式的处理我们将实现接口化,方便我们的管理:定义一个IMirror接口:

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

public interface IMirror
{
    void Draw(Image image,List uiVertices,MirrorType type);
}

Simpe下的顶点映射:

public class SimpleMirror : IMirror
{
    public void Draw(Image image,List uiVertices,MirrorType type)
    {
        ChangeVertices(image.rectTransform.rect,uiVertices,type);
        MirrorUtlis.Mirror(image.rectTransform.rect,uiVertices,type);
    }

    // 改变原有的顶点位置 (做一半映射) 如果是 Horizontal:左半部分 Vertical:上半部分 HorizontalAndVertical:左上四分之一
    private void ChangeVertices(Rect rect,List uiVertices,MirrorType type)
    {
        for (int i = 0; i < uiVertices.Count; i++)
        {
            UIVertex vertex = uiVertices[i];
            switch (type)
            {
                case MirrorType.Horizontal:
                    vertex = HorizontalVertex(rect, vertex);
                    break;
                case MirrorType.Vertical:
                    vertex = VerticalVertex(rect, vertex);
                    break;
                case MirrorType.HorizontalAndVertical:
                    vertex = HorizontalVertex(rect, vertex);
                    vertex = VerticalVertex(rect, vertex);
                    break;
            }
            uiVertices[i] = vertex;
        }
    }

    // 水平映射
    private UIVertex HorizontalVertex(Rect rect,UIVertex vertex)
    {
        vertex.position.x = (vertex.position.x + rect.x) / 2;// - rect.width / 2;
        return vertex;
    }
    
    // 垂直映射
    private UIVertex VerticalVertex(Rect rect,UIVertex vertex)
    {
        vertex.position.y = (rect.y + vertex.position.y) / 2 + rect.height / 2;
        return vertex;
    }
}

Sliced下的顶点映射:

我们可以看到如下映射的主要方法:

// 水平映射
private UIVertex HorizontalVertex(Rect rect,UIVertex vertex)
{
    if (vertex.position.x == s_VertScratch[0].x || vertex.position.x == s_VertScratch[1].x) return vertex;
    vertex.position.x -= rect.width / 2;
    return vertex;
}

 时机上非常简单,就是直接对 x 做矩形宽度/2 的平移,比较难的是我们需要知道什么顶点需要做平移?

这个需要看一下Image的源码是如何实现顶点的处理:

        /// 
        /// Generate vertices for a 9-sliced Image.
        /// 
        private void GenerateSlicedSprite(VertexHelper toFill)
        {
            if (!hasBorder)
            {
                GenerateSimpleSprite(toFill, false);
                return;
            }

            Vector4 outer, inner, padding, border;

            if (activeSprite != null)
            {
                outer = Sprites.DataUtility.GetOuterUV(activeSprite);
                inner = Sprites.DataUtility.GetInnerUV(activeSprite);
                padding = Sprites.DataUtility.GetPadding(activeSprite);
                border = activeSprite.border;
            }
            else
            {
                outer = Vector4.zero;
                inner = Vector4.zero;
                padding = Vector4.zero;
                border = Vector4.zero;
            }

            Rect rect = GetPixelAdjustedRect();

            Vector4 adjustedBorders = GetAdjustedBorders(border / multipliedPixelsPerUnit, rect);
            padding = padding / multipliedPixelsPerUnit;

            s_VertScratch[0] = new Vector2(padding.x, padding.y);
            s_VertScratch[3] = new Vector2(rect.width - padding.z, rect.height - padding.w);

            s_VertScratch[1].x = adjustedBorders.x;
            s_VertScratch[1].y = adjustedBorders.y;

            s_VertScratch[2].x = rect.width - adjustedBorders.z;
            s_VertScratch[2].y = rect.height - adjustedBorders.w;

            for (int i = 0; i < 4; ++i)
            {
                s_VertScratch[i].x += rect.x;
                s_VertScratch[i].y += rect.y;
            }

            ......
            ......
        }

这段源码不全我截取了,计算图片的位置信息,然后把4个顶点位置信息按顺序写进s_VertScratch数组中。这四个位置分别对应一下位置:

Unity Image - 镜像_第8张图片

即九宫格裁剪后映射到Image顶点上的四个位置,所以当我们向做水平映射的时候只需要平移和 3和4 x轴相等的顶点,与1和2 x轴相等的顶点保留原来的位置。如下图可以很直观的看出来

Unity Image - 镜像_第9张图片

至于怎么算出这四个九宫格映射的顶点就直接拷贝Image源码的实现就好了。

贴一下完整代码:

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

public class SlicedMirror : IMirror
{
    private Image image;
    
    // 九宫格的四个分界点
    private Vector2[] s_VertScratch = new Vector2[4];

    public void Draw(Image image,List uiVertices,MirrorType type)
    {
        this.image = image;
        SetVertScratch();
        ChangeVertices(image.rectTransform.rect,uiVertices,type);
        MirrorUtlis.Mirror(image.rectTransform.rect,uiVertices,type);
    }

    private void ChangeVertices(Rect rect,List uiVertices,MirrorType type)
    {
        for (int i = 0; i < uiVertices.Count; i++)
        {
            UIVertex vertex = uiVertices[i];
            switch (type)
            {
                case MirrorType.Horizontal:
                    vertex = HorizontalVertex(rect, vertex);
                    break;
                case MirrorType.Vertical:
                    vertex = VerticalVertex(rect, vertex);
                    break;
                case MirrorType.HorizontalAndVertical:
                    vertex = HorizontalVertex(rect, vertex);
                    vertex = VerticalVertex(rect, vertex);
                    break;
            }
            uiVertices[i] = vertex;
        }
    }

    // 水平映射
    private UIVertex HorizontalVertex(Rect rect,UIVertex vertex)
    {
        if (vertex.position.x == s_VertScratch[0].x || vertex.position.x == s_VertScratch[1].x) return vertex;
        vertex.position.x -= rect.width / 2;
        return vertex;
    }
    
    // 垂直映射
    private UIVertex VerticalVertex(Rect rect,UIVertex vertex)
    {
        if (vertex.position.y == s_VertScratch[2].y || vertex.position.y == s_VertScratch[3].y) return vertex;
        vertex.position.y += rect.height / 2;
        return vertex;
    }
    
    private void SetVertScratch()
    {
        Sprite activeSprite = image.sprite;
        Vector4 padding, border;

        if (activeSprite != null)
        {
            padding = UnityEngine.Sprites.DataUtility.GetPadding(activeSprite);
            border = activeSprite.border;
        }
        else
        {
            padding = Vector4.zero;
            border = Vector4.zero;
        }

        Rect rect = image.GetPixelAdjustedRect();

        var multipliedPixelsPerUnit = image.pixelsPerUnit * image.pixelsPerUnitMultiplier;
        Vector4 adjustedBorders = GetAdjustedBorders(border / multipliedPixelsPerUnit, rect);
        padding /= multipliedPixelsPerUnit;

        s_VertScratch[0] = new Vector2(padding.x, padding.y);
        s_VertScratch[3] = new Vector2(rect.width - padding.z, rect.height - padding.w);

        s_VertScratch[1].x = adjustedBorders.x;
        s_VertScratch[1].y = adjustedBorders.y;

        s_VertScratch[2].x = rect.width - adjustedBorders.z;
        s_VertScratch[2].y = rect.height - adjustedBorders.w;

        for (int i = 0; i < 4; ++i)
        {
            s_VertScratch[i].x += rect.x;
            s_VertScratch[i].y += rect.y;
        }
    }
    private Vector4 GetAdjustedBorders(Vector4 border, Rect adjustedRect)
    {
        Rect originalRect = image.rectTransform.rect;

        for (int axis = 0; axis <= 1; axis++)
        {
            float borderScaleRatio;
            if (originalRect.size[axis] != 0)
            {
                borderScaleRatio = adjustedRect.size[axis] / originalRect.size[axis];
                border[axis] *= borderScaleRatio;
                border[axis + 2] *= borderScaleRatio;
            }

            float combinedBorders = border[axis] + border[axis + 2];
            if (adjustedRect.size[axis] < combinedBorders && combinedBorders != 0)
            {
                borderScaleRatio = adjustedRect.size[axis] / combinedBorders;
                border[axis] *= borderScaleRatio;
                border[axis + 2] *= borderScaleRatio;
            }
        }
        return border;
    }
}

Tiled:模式下的映射

在平铺模式下顶点都是完整的,不需要做镜像处理,只需要修改没一块对应的UV对称即可,我们固定开始位置为1,不做翻转,那么

2位置所构成的顶点UV.y:就需要做对称处理

4位置所构成的顶点UV.x:就需要做对称处理

3位置所构成的顶点UV.x和y :都需要做对称处理

Unity Image - 镜像_第10张图片

如何判断某几个顶点的UV需要做对称?
我们知道一个三角面由三个顶点构成,那么我么只需要找出三个顶点的中心位置,假设sprite的宽高都为w = 100,h = 100,构成的三角形区域的中心点分别为

1位置 =>(50,50),

2位置 => (50,150),

3位置 => (150,150),

4位置 => (150,50),

我们对中心的的

1 => x / W = 0.5

2 => x / W = 1.5

。。

我们对结果 %2 那么 结果为 1 的就需要翻转了;

uv怎么翻转
outerUv = UnityEngine.Sprites.DataUtility.GetOuterUV(image.sprite);

outerUV中的  x,y就代表右下角的点,z就代表宽,w:代表高,假设A镜像UV后的点为B,那么就满足:

A 到 (0,0)的距离  == B到(0+z)的距离,所以

镜像后的 A.x = outer.z -( A.x - outerUv.x )

Unity Image - 镜像_第11张图片

贴一下完整代码

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

public class TiledMirror : IMirror
{

    private Vector4 outerUv;
    public void Draw(Image image,List uiVertices,MirrorType type)
    {
        outerUv = UnityEngine.Sprites.DataUtility.GetOuterUV(image.sprite);
        ChangeUv(uiVertices,type);
    }

    // uv翻转
    private void ChangeUv(List uiVertices,MirrorType type)
    {
        Vector3 cellMinP = uiVertices[0].position;
        Vector3 cellMaxP = uiVertices[2].position;
        float w = cellMaxP.x - cellMinP.x;
        float h = cellMaxP.y - cellMinP.y;
        
        for (int i = 0; i < uiVertices.Count; i+= 3)
        {
            UIVertex v1 = uiVertices[i];
            UIVertex v2 = uiVertices[i+1];
            UIVertex v3 = uiVertices[i+2];
            
            float centerX = GetCenter(v1, v2, v3, true) - cellMaxP.x;
            float centerY = GetCenter(v1, v2, v3, false) - cellMaxP.y;
            
            bool changeX = Mathf.Ceil(centerX / w) % 2 != 0;
            bool changeY = Mathf.Ceil(centerY / h) % 2 != 0;
            
            if (changeX && (type == MirrorType.Horizontal || type == MirrorType.HorizontalAndVertical))
            {
  
                v1 = HorizontalUv(v1);
                v2 = HorizontalUv(v2);
                v3 = HorizontalUv(v3);
            }
            
            if (changeY && (type == MirrorType.Vertical || type == MirrorType.HorizontalAndVertical))
            {
                v1 = VerticalUv(v1);
                v2 = VerticalUv(v2);
                v3 = VerticalUv(v3);
            }
            
            uiVertices[i] = v1;
            uiVertices[i + 1] = v2;
            uiVertices[i + 2] = v3;
        }
    }

    // 获取三个顶点的中心位置
    private float GetCenter(UIVertex v1,UIVertex v2,UIVertex v3,bool isX)
    {
        float min = Mathf.Min(
            Mathf.Min(isX ? v1.position.x : v1.position.y,isX ? v2.position.x : v2.position.y),
            Mathf.Min(isX ? v1.position.x : v1.position.y,isX ? v3.position.x : v3.position.y));
        float max = Mathf.Max(
            Mathf.Max(isX ? v1.position.x : v1.position.y,isX ? v2.position.x : v2.position.y),
            Mathf.Max(isX ? v1.position.x : v1.position.y,isX ? v3.position.x : v3.position.y));
        return (min + max) / 2;
    }

    private UIVertex HorizontalUv(UIVertex vertex)
    {
        vertex.uv0.x = outerUv.x + outerUv.z - vertex.uv0.x;
        return vertex;
    }
    
    private UIVertex VerticalUv(UIVertex vertex)
    {
        vertex.uv0.y = outerUv.y + outerUv.w - vertex.uv0.y;
        return vertex;
    }
    
    
}

总结:

实现过程中,思路理清之后实现基本上是不难,但是需要去理解Unity Image的实现,针对绘制不同模式的生成网格顶点的实现,知道图篇是怎么绘制上去的,三个顶点构成一个面,Rect中的(x,y,z,w)分别代表什么。然后就是计算计算。

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