Unity工程里图片的RGB和Alpha通道的分离，及显示带有Alpha通道贴图的Material
发表于2017-11-03
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()
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string[] paths = Directory.GetFiles(Application.dataPath, "*.*", SearchOption.AllDirectories);
foreach (string path in paths)
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if (!string.IsNullOrEmpty(path) && IsTextureFile(path)) //full name
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SeperateRGBAandlphaChannel(path);
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[MenuItem("EffortForETC1/Show Materials Having Textures with Alpha Chanel")]
static void ShowMaterialsHavingTextureswithAlphaChanel()
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CalculateTexturesAlphaChannelDic();
string[] matpaths = Directory.GetFiles(Application.dataPath, "*.mat", SearchOption.AllDirectories);
foreach (string matpath in matpaths)
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string propermatpath = GetRelativeAssetPath(matpath);
Material mat = (Material)AssetDatabase.LoadAssetAtPath(propermatpath, typeof(Material));
if (mat)
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string[] alphatexpaths = GetMaterialTexturesHavingAlphaChannel(mat);
if (alphatexpaths.Length == 0)
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continue;
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Debug.Log("Material having texture(s) with Alpha channel : " propermatpath);
foreach (string alphatexpath in alphatexpaths)
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Debug.Log(alphatexpath " in " propermatpath);
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else
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Debug.LogError("Load material failed : " matpath);
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Debug.Log("Finish!");
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#region inspect material
static string[] GetMaterialTexturesHavingAlphaChannel(Material _mat)
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List<string> alphatexpaths = new List<string>();
string[] texpaths = GetMaterialTexturePaths(_mat);
foreach (string texpath in texpaths)
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if (texturesAlphaDic[texpath])
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alphatexpaths.Add(texpath);
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return alphatexpaths.ToArray();
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static string[] GetMaterialTexturePaths(Material _mat)
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List<string> results = new List<string>();
Object[] roots = new Object[] ｛ _mat ｝;
Object[] dependObjs = EditorUtility.CollectDependencies(roots);
foreach (Object dependObj in dependObjs)
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if (dependObj.GetType() == typeof(Texture2D))
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string texpath = AssetDatabase.GetAssetPath(dependObj.GetInstanceID());
results.Add(texpath);
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return results.ToArray();
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#endregion
static void CalculateTexturesAlphaChannelDic()
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string[] paths = Directory.GetFiles(Application.dataPath, "*.*", SearchOption.AllDirectories);
foreach (string path in paths)
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if (!string.IsNullOrEmpty(path) && IsTextureFile(path)) //full name
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string assetRelativePath = GetRelativeAssetPath(path);
SetTextureReadable(assetRelativePath);
Texture2D sourcetex = AssetDatabase.LoadAssetAtPath(assetRelativePath, typeof(Texture2D)) as Texture2D;
if (!sourcetex) //make sure the file is really Texture2D which can be loaded as Texture2D.
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continue;
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if (HasAlphaChannel(sourcetex))
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AddValueToDic(assetRelativePath, true);
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else
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AddValueToDic(assetRelativePath, false);
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static void AddValueToDic(string _key, bool _val)
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if (texturesAlphaDic.ContainsKey(_key))
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texturesAlphaDic[_key] = _val;
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else
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texturesAlphaDic.Add(_key, _val);
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#region process texture
static void SeperateRGBAandlphaChannel(string _texPath)
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string assetRelativePath = GetRelativeAssetPath(_texPath);
SetTextureReadable(assetRelativePath);
Texture2D sourcetex = AssetDatabase.LoadAssetAtPath(assetRelativePath, typeof(Texture2D)) as Texture2D; //not just the textures under Resources file
if (!sourcetex)
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Debug.Log("Load Texture Failed : " assetRelativePath);
return;
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if (!HasAlphaChannel(sourcetex))
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Debug.Log("Texture does not have Alpha channel : " assetRelativePath);
return;
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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)
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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);
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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);
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static bool HasAlphaChannel(Texture2D _tex)
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for (int i = 0; i < _tex.width; i)
for (int j = 0; j < _tex.height; j)
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Color color = _tex.GetPixel(i, j);
float alpha = color.a;
if (alpha < 1.0f - 0.001f)
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return true;
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return false;
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static void SetTextureReadable(string _relativeAssetPath)
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string postfix = GetFilePostfix(_relativeAssetPath);
if (postfix == ".dds") // no need to set .dds file. Using TextureImporter to .dds file would get casting type error.
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return;
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TextureImporter ti = (TextureImporter)TextureImporter.GetAtPath(_relativeAssetPath);
ti.isReadable = true;
AssetDatabase.ImportAsset(_relativeAssetPath);
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#endregion
#region string or path helper
static bool IsTextureFile(string _path)
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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");
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static string GetRGBTexPath(string _texPath)
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return GetTexPath(_texPath, "_RGB.");
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static string GetAlphaTexPath(string _texPath)
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return GetTexPath(_texPath, "_Alpha.");
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static string GetTexPath(string _texPath, string _texRole)
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string result = _texPath.Replace(".", _texRole);
string postfix = GetFilePostfix(_texPath);
return result.Replace(postfix, ".png");
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static string GetRelativeAssetPath(string _fullPath)
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_fullPath = GetRightFormatPath(_fullPath);
int idx = _fullPath.IndexOf("Assets");
string assetRelativePath = _fullPath.Substring(idx);
return assetRelativePath;
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static string GetRightFormatPath(string _path)
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return _path.Replace("\\", "/");
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static string GetFilePostfix(string _filepath) //including '.' eg ".tga", ".dds"
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string postfix = "";
int idx = _filepath.LastIndexOf('.');
if (idx > 0 && idx < _filepath.Length)
postfix = _filepath.Substring(idx, _filepath.Length - idx);
return postfix;
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#endregion
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这篇文章里有两个明显的问题：
1. 处理Alpha贴图时是一个像素一个像素地处理，用Texture.SetPixel()函数。推荐批量处理，用Texture.SetPixels()函数。推荐批量处理，用Texture.SetPixels()函数。
2. Alpha贴图只存储Alpha通道信息，信息熵较低，理论上可以缩减一些尺寸来存储，但简单地按比例缩小可能会有问题，例如Alpha通道像素相邻一直为黑白黑白的情况，会严重失真，这里的取样需要考虑下。
【改进版】Unity工程里图片的RGB和Alpha通道的分离
http://blog.csdn.net/e295166319/article/details/52624155