Unity中如何计算带minimap的贴图资源的大小

    /// <summary>
    /// 计算贴图大小,包含mipmap内存的叠加
    /// </summary>
    /// <param name="tTexture"></param>
    /// <returns></returns>
    public static int CalculateTextureSizeBytes(Texture tTexture)
    {

        int tWidth = tTexture.width;
        int tHeight = tTexture.height;
        if (tTexture is Texture2D)
        {
            Texture2D tTex2D = tTexture as Texture2D;
            int bitsPerPixel = GetBitsPerPixel(tTex2D.format);
            int mipMapCount = tTex2D.mipmapCount;
            int mipLevel = 1;
            int tSize = 0;
            while (mipLevel <= mipMapCount)
            {
                tSize += tWidth * tHeight * bitsPerPixel / 8;
                tWidth = tWidth / 2;
                tHeight = tHeight / 2;
                mipLevel++;
            }
            return tSize;
        }
        return 0;
    }

    /// <summary>
    /// 计算贴图大小,包含mipmap内存的叠加,指定贴图格式
    /// </summary>
    /// <param name="tTexture"></param>
    /// <returns></returns>
    public static int CalculateTextureSizeBytesByFormat(Texture tTexture, TextureImporterFormat format)
    {
        int tWidth = tTexture.width;
        int tHeight = tTexture.height;
        if (tTexture is Texture2D)
        {
            Texture2D tTex2D = tTexture as Texture2D;
            if (TextureImporterFormat.Automatic == format)
            {
                Debug.LogError("------------------>有贴图格式未设置: 贴图名称:" + tTexture.name);
            }
            int bitsPerPixel = GetBitsPerPixelForImportFormat(format);
            int mipMapCount = tTex2D.mipmapCount;
            int mipLevel = 1;
            int tSize = 0;
            while (mipLevel <= mipMapCount)
            {
                tSize += tWidth * tHeight * bitsPerPixel / 8;
                tWidth = tWidth / 2;
                tHeight = tHeight / 2;
                mipLevel++;
            }
            return tSize;
        }
        return 0;
    }

    /// <summary>
    /// 获取对应个是贴图的位大小
    /// </summary>
    /// <param name="format"></param>
    /// <returns></returns>
    public static int GetBitsPerPixel(TextureFormat format)
    {
        switch (format)
        {
            case TextureFormat.Alpha8: //     Alpha-only texture format.
                return 8;
            case TextureFormat.ARGB4444: //     A 16 bits/pixel texture format. Texture stores color with an alpha channel.
                return 16;
            case TextureFormat.RGBA4444: //     A 16 bits/pixel texture format.
                return 16;
            case TextureFormat.RGB24:   // A color texture format.
                return 24;
            case TextureFormat.RGBA32:  //Color with an alpha channel texture format.
                return 32;
            case TextureFormat.ARGB32:  //Color with an alpha channel texture format.
                return 32;
            case TextureFormat.RGB565:  //     A 16 bit color texture format.
                return 16;
            case TextureFormat.DXT1:    // Compressed color texture format.
                return 4;
            case TextureFormat.DXT5:    // Compressed color with alpha channel texture format.
                return 8;
            case TextureFormat.PVRTC_RGB2://     PowerVR (iOS) 2 bits/pixel compressed color texture format.
                return 2;
            case TextureFormat.PVRTC_RGBA2://     PowerVR (iOS) 2 bits/pixel compressed with alpha channel texture format
                return 2;
            case TextureFormat.PVRTC_RGB4://     PowerVR (iOS) 4 bits/pixel compressed color texture format.
                return 4;
            case TextureFormat.PVRTC_RGBA4://     PowerVR (iOS) 4 bits/pixel compressed with alpha channel texture format
                return 4;
            case TextureFormat.ETC_RGB4://     ETC (GLES2.0) 4 bits/pixel compressed RGB texture format.
                return 4;
            case TextureFormat.ETC2_RGBA8://     ATC (ATITC) 8 bits/pixel compressed RGB texture format.
                return 8;
            case TextureFormat.BGRA32://     Format returned by iPhone camera
                return 32;
        }
        return 0;
    }

    public static int GetBitsPerPixelForImportFormat(TextureImporterFormat format)
    {
        switch (format)
        {
            case TextureImporterFormat.Alpha8: //     Alpha-only texture format.
                return 8;
            case TextureImporterFormat.RGB24:   // A color texture format.
                return 24;
            case TextureImporterFormat.RGBA32:  //Color with an alpha channel texture format.
                return 32;
            case TextureImporterFormat.ARGB32:  //Color with an alpha channel texture format.
                return 32;
            case TextureImporterFormat.RGBA16:  //     A 16 bit color texture format.
                return 16;
            case TextureImporterFormat.RGB16:  //     A 16 bit color texture format.
                return 16;
            case TextureImporterFormat.DXT1:    // Compressed color texture format.
                return 4;
            case TextureImporterFormat.DXT5:    // Compressed color with alpha channel texture format.
                return 8;
            case TextureImporterFormat.PVRTC_RGB2://     PowerVR (iOS) 2 bits/pixel compressed color texture format.
                return 2;
            case TextureImporterFormat.PVRTC_RGBA2://     PowerVR (iOS) 2 bits/pixel compressed with alpha channel texture format
                return 2;
            case TextureImporterFormat.PVRTC_RGB4://     PowerVR (iOS) 4 bits/pixel compressed color texture format.
                return 4;
            case TextureImporterFormat.PVRTC_RGBA4://     PowerVR (iOS) 4 bits/pixel compressed with alpha channel texture format
                return 4;
            case TextureImporterFormat.ETC_RGB4://     ETC (GLES2.0) 4 bits/pixel compressed RGB texture format.
                return 4;
            case TextureImporterFormat.ETC2_RGB4://     ETC (GLES3.0) 4 bits/pixel compressed RGB texture format.
                return 4;
            case TextureImporterFormat.ETC2_RGBA8://     ETC (GLES3.0) 8 bits/pixel compressed RGBA texture format.
                return 8;
            case TextureImporterFormat.Automatic://     没有设置贴图格式，默认给4bit.
                return 4;
        }
        return 0;
    }