Unity --- 在原目录中，将选中的Texture剥离为rgb和alpha

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System;
using UObject = UnityEngine.Object;
using System.IO;

public class lgs
{
    [MenuItem("Assets/AlphaSpliter ")]
    static void AlphaSpliter()
    {
        UObject[] objs = Selection.objects;
        for (int i = 0; i < objs.Length; i++)
        {
            Texture tex = objs[i] as Texture;
            CreateRGBTexture(tex);
            CreateAlphaTexture(tex as Texture2D);
        }
    }

    static void CreateAlphaTexture(Texture2D src)
    {
        if (null == src)
            throw new ArgumentNullException("src");

        //create alpha texture
        var srcPixels = src.GetPixels();
        var targetPixels = new Color[srcPixels.Length];
        for (int i = 0, iMax = srcPixels.Length; i < iMax; ++i)
        {
            float r = srcPixels[i].a;
            targetPixels[i] = new Color(r, r, r);
        }

        Texture2D alphaTex = new Texture2D(src.width, src.height, TextureFormat.ARGB32, false);
        alphaTex.SetPixels(targetPixels);
        alphaTex.Apply();

        //save alpha texture
        string srcPath = AssetDatabase.GetAssetPath(src);
        string ext = Path.GetExtension(srcPath);
        string newPath = string.Format("{0}{1}{2}", srcPath.Substring(0, srcPath.Length - ext.Length), "_alpha", ext);
        string fullPath = GetFullPath(newPath);
        var bytes = alphaTex.EncodeToPNG();
        File.WriteAllBytes(fullPath, bytes);

        AssetDatabase.SaveAssets();
        AssetDatabase.Refresh();

        int size = Mathf.Max(src.width, src.height, 32);
        Setting(newPath, size, TextureImporterFormat.ETC_RGB4, TextureImporterFormat.PVRTC_RGB4);
    }

    static void CreateRGBTexture(Texture src)
    {
        if (null == src)
            throw new ArgumentNullException("src");

        string srcPath = AssetDatabase.GetAssetPath(src);
        string ext = Path.GetExtension(srcPath);
        string newPath = string.Format("{0}{1}{2}", srcPath.Substring(0, srcPath.Length - ext.Length), "_rgb", ext);


        AssetDatabase.DeleteAsset(newPath);
        AssetDatabase.CopyAsset(srcPath, newPath);
        AssetDatabase.ImportAsset(newPath);

        int size = Mathf.Max(src.width, src.height, 32);
        Setting(newPath, size, TextureImporterFormat.ETC_RGB4, TextureImporterFormat.PVRTC_RGB4);
    }

    static void Setting(string assetPath, int maxSize, TextureImporterFormat androidFormat, TextureImporterFormat iosFormat)
    {
        var texImporter = AssetImporter.GetAtPath(assetPath) as TextureImporter;
        {
            texImporter.npotScale = TextureImporterNPOTScale.ToNearest;
            texImporter.isReadable = false;
            texImporter.mipmapEnabled = false;
            texImporter.alphaIsTransparency = true;
            texImporter.wrapMode = TextureWrapMode.Clamp;
            texImporter.filterMode = FilterMode.Bilinear;
            texImporter.anisoLevel = 4;    //纹理的各向异性滤波水平
            texImporter.SetPlatformTextureSettings("Android", maxSize, androidFormat);
            texImporter.SetPlatformTextureSettings("iPhone", maxSize, iosFormat);
            texImporter.SetPlatformTextureSettings("Standalone", maxSize, TextureImporterFormat.ARGB32);
        }

        AssetDatabase.ImportAsset(assetPath);
        AssetDatabase.SaveAssets();
    }

    /// <summary>
    /// asset path 转 full path
    /// </summary>
    public static string GetFullPath(string assetPath)
    {
        if (string.IsNullOrEmpty(assetPath))
            return "";

        string p = Application.dataPath + assetPath.Substring(6);
        return p.Replace("\", "/");
    }

    /// <summary>
    /// full path 转 asset path
    /// </summary>
    public static string GetAssetPath(string fullPath)
    {
        if (string.IsNullOrEmpty(fullPath))
            return "";

        fullPath = fullPath.Replace("\", "/");
        return fullPath.StartsWith("Assets/") ?
            fullPath :
            "Assets" + fullPath.Substring(Application.dataPath.Length);
    }
}