Unity工程里图片的RGB和Alpha通道的分离，以及显示所有带有Alpha通道贴图的Material_unity3d rgb通道如果查看

背景：ETC1图片格式的罪孽，不支持Alpha通道。于是程序员们将一些气力浪费在Alpha通道的处理上。 为了能使用ETC1，同时某些透明效果必须有Alpha通道，一般的处理方式是将RGB和Alpha分为两张图片分别储存。 只存Alpha通道的图片及RGB都为要存的Alpha值，因为熵比较小，图片尺寸也可以相应减小一些。

要做的工作：

1. 将带有Alpha通道的图片，另存为两张图片，一张只存RGB信息，另一张只存Alpha信息。建议保持为图片原目录，名称加后缀“_RGB”, "_Alpha"。

2. 带有Alpha通道的图片，所用的Shader要更新为支持RGB和Alpha信息分别从两张不同图片读取的shader。这个功能，因为不能的Material的Shader会很不一样，因此，不用程序来强硬指定了。但程序起码需要给出提示，工程中哪些Material用到了哪些带有Alpha通道的图片。

不罗嗦了，直接上代码。

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using System.IO;
using System.Reflection;
 
public class MaterialTextureForETC1{
 
    public static float sizeScale = 0.5f;   //the size decrease scale for alphaTexture
    public static Dictionary<string, bool> texturesAlphaDic = new Dictionary<string, bool>();
 
    [MenuItem("EffortForETC1/Seperate RGB and Alpha Channel for All Textures")]
    static void SeperateAllTexturesRGBandAlphaChannel()
    {
        string[] paths = Directory.GetFiles(Application.dataPath, "*.*", SearchOption.AllDirectories);
        foreach (string path in paths)
        {
            if (!string.IsNullOrEmpty(path) && IsTextureFile(path))   //full name
            {
                SeperateRGBAandlphaChannel(path);
            }
        } 
    }
 
    [MenuItem("EffortForETC1/Show Materials Having Textures with Alpha Chanel")]
    static void ShowMaterialsHavingTextureswithAlphaChanel()
    {
        CalculateTexturesAlphaChannelDic();
        string[] matpaths = Directory.GetFiles(Application.dataPath, "*.mat", SearchOption.AllDirectories);
        foreach (string matpath in matpaths)
        {
            string propermatpath = GetRelativeAssetPath(matpath);
            Material mat = (Material)Resources.LoadAssetAtPath(propermatpath, typeof(Material));
            if (mat)
            {
                string[] alphatexpaths = GetMaterialTexturesHavingAlphaChannel(mat);
                if (alphatexpaths.Length == 0)
                {
                    continue;
                }
                Debug.Log("Material having texture(s) with Alpha channel : " + propermatpath);
                foreach (string alphatexpath in alphatexpaths)
                {
                    Debug.Log(alphatexpath + " in " + propermatpath);
                }
            }
            else
            {
                Debug.LogError("Load material failed : " + matpath);
            }
        }
        Debug.Log("Finish!");     
    }
 
 
    #region inspect material
 
    static string[] GetMaterialTexturesHavingAlphaChannel(Material _mat)
    {
        List<string> alphatexpaths = new List<string>();
        string[] texpaths = GetMaterialTexturePaths(_mat);
        foreach (string texpath in texpaths)
        {
            if (texturesAlphaDic[texpath])
            {
                alphatexpaths.Add(texpath);
            }
        }
 
        return alphatexpaths.ToArray();
    }
 
    static string[] GetMaterialTexturePaths(Material _mat)
    {
        List<string> results = new List<string>();
        Object[] roots = new Object[] { _mat };
        Object[] dependObjs = EditorUtility.CollectDependencies(roots);
        foreach (Object dependObj in dependObjs)
        {
            if (dependObj.GetType() == typeof(Texture2D))
            {
                string texpath = AssetDatabase.GetAssetPath(dependObj.GetInstanceID());
                results.Add(texpath);
            }
        }
        return results.ToArray();
    }
 
    #endregion
 
 
    static void CalculateTexturesAlphaChannelDic()
    {
        string[] paths = Directory.GetFiles(Application.dataPath, "*.*", SearchOption.AllDirectories);
        foreach (string path in paths)
        {
            if (!string.IsNullOrEmpty(path) && IsTextureFile(path))   //full name
            {
                string assetRelativePath = GetRelativeAssetPath(path);
                SetTextureReadable(assetRelativePath);
                Texture2D sourcetex = Resources.LoadAssetAtPath(assetRelativePath, typeof(Texture2D)) as Texture2D;  
                if (!sourcetex)  //make sure the file is really Texture2D which can be loaded as Texture2D.
                {
                    continue;
                }
                if (HasAlphaChannel(sourcetex))
                {
                    AddValueToDic(assetRelativePath, true);                                    
                }
                else
                {
                    AddValueToDic(assetRelativePath, false);  
                }
            }
        } 
    }
 
    static void AddValueToDic(string _key, bool _val)
    {
        if (texturesAlphaDic.ContainsKey(_key))
        {
            texturesAlphaDic[_key] = _val;
        }
        else
        {
            texturesAlphaDic.Add(_key, _val);
        }
    }
 
 
    #region process texture
 
    static void SeperateRGBAandlphaChannel(string _texPath)
    {
        string assetRelativePath = GetRelativeAssetPath(_texPath);
        SetTextureReadable(assetRelativePath);
        Texture2D sourcetex = Resources.LoadAssetAtPath(assetRelativePath, typeof(Texture2D)) as Texture2D;  //not just the textures under Resources file
        if (!sourcetex)
        {
            Debug.Log("Load Texture Failed : " + assetRelativePath);
            return;
        }
        if (!HasAlphaChannel(sourcetex))
        {
            Debug.Log("Texture does not have Alpha channel : " + assetRelativePath);
            return;
        }
 
        Texture2D rgbTex = new Texture2D(sourcetex.width, sourcetex.height, TextureFormat.RGB24, true);
        Texture2D alphaTex = new Texture2D((int)(sourcetex.width * sizeScale), (int)(sourcetex.height * sizeScale), TextureFormat.RGB24, true);
 
        for (int i = 0; i < sourcetex.width; ++i)
            for (int j = 0; j < sourcetex.height; ++j)
            {
                Color color = sourcetex.GetPixel(i, j);
                Color rgbColor = color;
                Color alphaColor = color;
                alphaColor.r = color.a;
                alphaColor.g = color.a;
                alphaColor.b = color.a;
                rgbTex.SetPixel(i, j, rgbColor);
                alphaTex.SetPixel((int)(i * sizeScale), (int)(j * sizeScale), alphaColor);
            }
 
        rgbTex.Apply();
        alphaTex.Apply();
 
        byte[] bytes = rgbTex.EncodeToPNG();
        File.WriteAllBytes(GetRGBTexPath(_texPath), bytes);
        bytes = alphaTex.EncodeToPNG();
        File.WriteAllBytes(GetAlphaTexPath(_texPath), bytes);
        Debug.Log("Succeed to seperate RGB and Alpha channel for texture : " + assetRelativePath);
    }
 
    static bool HasAlphaChannel(Texture2D _tex)
    {
        for (int i = 0; i < _tex.width; ++i)
            for (int j = 0; j < _tex.height; ++j)
            {
                Color color = _tex.GetPixel(i, j);
                float alpha = color.a;
                if (alpha < 1.0f - 0.001f)
                {
                    return true;
                }
            }
        return false;
    }
 
    static void SetTextureReadable(string _relativeAssetPath)
    {
        string postfix = GetFilePostfix(_relativeAssetPath);
        if (postfix == ".dds")    // no need to set .dds file.  Using TextureImporter to .dds file would get casting type error.
        {
            return;
        }
 
        TextureImporter ti = (TextureImporter)TextureImporter.GetAtPath(_relativeAssetPath);
        ti.isReadable = true;
        AssetDatabase.ImportAsset(_relativeAssetPath);
    }
   
    #endregion
    
 
    #region string or path helper
 
    static bool IsTextureFile(string _path)
    {
        string path = _path.ToLower();
        return path.EndsWith(".psd") || path.EndsWith(".tga") || path.EndsWith(".png") || path.EndsWith(".jpg") || path.EndsWith(".dds") || path.EndsWith(".bmp") || path.EndsWith(".tif") || path.EndsWith(".gif");
    }
 
    static string GetRGBTexPath(string _texPath)
    {
        return GetTexPath(_texPath, "_RGB.");
    }
 
    static string GetAlphaTexPath(string _texPath)
    {
        return GetTexPath(_texPath, "_Alpha.");
    }
 
    static string GetTexPath(string _texPath, string _texRole)
    {
        string result = _texPath.Replace(".", _texRole);
        string postfix = GetFilePostfix(_texPath);
        return result.Replace(postfix, ".png");
    }
 
    static string GetRelativeAssetPath(string _fullPath)
    {
        _fullPath = GetRightFormatPath(_fullPath);
        int idx = _fullPath.IndexOf("Assets");
        string assetRelativePath = _fullPath.Substring(idx);
        return assetRelativePath;
    }
 
    static string GetRightFormatPath(string _path)
    {
        return _path.Replace("\\", "/");
    }
 
    static string GetFilePostfix(string _filepath)   //including '.' eg ".tga", ".dds"
    {
        string postfix = "";
        int idx = _filepath.LastIndexOf('.');
        if (idx > 0 && idx < _filepath.Length)
            postfix = _filepath.Substring(idx, _filepath.Length - idx);
        return postfix;
    }
 
    #endregion   
}

上面的代码中，图片的处理，用的是已经整合进Unity的有限的图片处理功能，分离RGB和Alpha通道的图片都被存为了.png格式。其实可以将C#的System.Drawing.dll导入到工程里，用C#原生的Bitmap类来处理图片。

.dds格式图片的处理比较特殊。一般用Texture2D.GetPixel()等函数处理Texture2D时，需要设置Texture的Import属性里的Readable，但.dds格式的图片不用处理。同时，Unity只支持Int格式的dds, float32格式的.dds不支持。

【改进版】Unity工程里图片的RGB和Alpha通道的分离

http://blog.csdn.net/u010153703/article/details/45502895