将DXGI_FORMAT转换为bpp

Question

如何在不进行枚举的情况下将DXGI_FORMAT转换为bpp (每像素位)值？(见格式

例如：

DXGI_FORMAT_R10G10B10A2_UNORM -> 32
DXGI_FORMAT_B5G5R5A1_UNORM -> 16

Answer 1

DirectXTex实现了这个实用程序函数，我在DirectX工具包 for DDSTextureLoader中实现了它。

//-------------------------------------------------------------------------------------
// Returns bits-per-pixel for a given DXGI format, or 0 on failure
//-------------------------------------------------------------------------------------
_Use_decl_annotations_
size_t DirectX::BitsPerPixel(DXGI_FORMAT fmt)
{
    switch (static_cast<int>(fmt))
    {
    case DXGI_FORMAT_R32G32B32A32_TYPELESS:
    case DXGI_FORMAT_R32G32B32A32_FLOAT:
    case DXGI_FORMAT_R32G32B32A32_UINT:
    case DXGI_FORMAT_R32G32B32A32_SINT:
        return 128;

    case DXGI_FORMAT_R32G32B32_TYPELESS:
    case DXGI_FORMAT_R32G32B32_FLOAT:
    case DXGI_FORMAT_R32G32B32_UINT:
    case DXGI_FORMAT_R32G32B32_SINT:
        return 96;

    case DXGI_FORMAT_R16G16B16A16_TYPELESS:
    case DXGI_FORMAT_R16G16B16A16_FLOAT:
    case DXGI_FORMAT_R16G16B16A16_UNORM:
    case DXGI_FORMAT_R16G16B16A16_UINT:
    case DXGI_FORMAT_R16G16B16A16_SNORM:
    case DXGI_FORMAT_R16G16B16A16_SINT:
    case DXGI_FORMAT_R32G32_TYPELESS:
    case DXGI_FORMAT_R32G32_FLOAT:
    case DXGI_FORMAT_R32G32_UINT:
    case DXGI_FORMAT_R32G32_SINT:
    case DXGI_FORMAT_R32G8X24_TYPELESS:
    case DXGI_FORMAT_D32_FLOAT_S8X24_UINT:
    case DXGI_FORMAT_R32_FLOAT_X8X24_TYPELESS:
    case DXGI_FORMAT_X32_TYPELESS_G8X24_UINT:
    case DXGI_FORMAT_Y416:
    case DXGI_FORMAT_Y210:
    case DXGI_FORMAT_Y216:
        return 64;

    case DXGI_FORMAT_R10G10B10A2_TYPELESS:
    case DXGI_FORMAT_R10G10B10A2_UNORM:
    case DXGI_FORMAT_R10G10B10A2_UINT:
    case DXGI_FORMAT_R11G11B10_FLOAT:
    case DXGI_FORMAT_R8G8B8A8_TYPELESS:
    case DXGI_FORMAT_R8G8B8A8_UNORM:
    case DXGI_FORMAT_R8G8B8A8_UNORM_SRGB:
    case DXGI_FORMAT_R8G8B8A8_UINT:
    case DXGI_FORMAT_R8G8B8A8_SNORM:
    case DXGI_FORMAT_R8G8B8A8_SINT:
    case DXGI_FORMAT_R16G16_TYPELESS:
    case DXGI_FORMAT_R16G16_FLOAT:
    case DXGI_FORMAT_R16G16_UNORM:
    case DXGI_FORMAT_R16G16_UINT:
    case DXGI_FORMAT_R16G16_SNORM:
    case DXGI_FORMAT_R16G16_SINT:
    case DXGI_FORMAT_R32_TYPELESS:
    case DXGI_FORMAT_D32_FLOAT:
    case DXGI_FORMAT_R32_FLOAT:
    case DXGI_FORMAT_R32_UINT:
    case DXGI_FORMAT_R32_SINT:
    case DXGI_FORMAT_R24G8_TYPELESS:
    case DXGI_FORMAT_D24_UNORM_S8_UINT:
    case DXGI_FORMAT_R24_UNORM_X8_TYPELESS:
    case DXGI_FORMAT_X24_TYPELESS_G8_UINT:
    case DXGI_FORMAT_R9G9B9E5_SHAREDEXP:
    case DXGI_FORMAT_R8G8_B8G8_UNORM:
    case DXGI_FORMAT_G8R8_G8B8_UNORM:
    case DXGI_FORMAT_B8G8R8A8_UNORM:
    case DXGI_FORMAT_B8G8R8X8_UNORM:
    case DXGI_FORMAT_R10G10B10_XR_BIAS_A2_UNORM:
    case DXGI_FORMAT_B8G8R8A8_TYPELESS:
    case DXGI_FORMAT_B8G8R8A8_UNORM_SRGB:
    case DXGI_FORMAT_B8G8R8X8_TYPELESS:
    case DXGI_FORMAT_B8G8R8X8_UNORM_SRGB:
    case DXGI_FORMAT_AYUV:
    case DXGI_FORMAT_Y410:
    case DXGI_FORMAT_YUY2:
    case XBOX_DXGI_FORMAT_R10G10B10_7E3_A2_FLOAT:
    case XBOX_DXGI_FORMAT_R10G10B10_6E4_A2_FLOAT:
    case XBOX_DXGI_FORMAT_R10G10B10_SNORM_A2_UNORM:
        return 32;

    case DXGI_FORMAT_P010:
    case DXGI_FORMAT_P016:
    case XBOX_DXGI_FORMAT_D16_UNORM_S8_UINT:
    case XBOX_DXGI_FORMAT_R16_UNORM_X8_TYPELESS:
    case XBOX_DXGI_FORMAT_X16_TYPELESS_G8_UINT:
    case WIN10_DXGI_FORMAT_V408:
        return 24;

    case DXGI_FORMAT_R8G8_TYPELESS:
    case DXGI_FORMAT_R8G8_UNORM:
    case DXGI_FORMAT_R8G8_UINT:
    case DXGI_FORMAT_R8G8_SNORM:
    case DXGI_FORMAT_R8G8_SINT:
    case DXGI_FORMAT_R16_TYPELESS:
    case DXGI_FORMAT_R16_FLOAT:
    case DXGI_FORMAT_D16_UNORM:
    case DXGI_FORMAT_R16_UNORM:
    case DXGI_FORMAT_R16_UINT:
    case DXGI_FORMAT_R16_SNORM:
    case DXGI_FORMAT_R16_SINT:
    case DXGI_FORMAT_B5G6R5_UNORM:
    case DXGI_FORMAT_B5G5R5A1_UNORM:
    case DXGI_FORMAT_A8P8:
    case DXGI_FORMAT_B4G4R4A4_UNORM:
    case WIN10_DXGI_FORMAT_P208:
    case WIN10_DXGI_FORMAT_V208:
        return 16;

    case DXGI_FORMAT_NV12:
    case DXGI_FORMAT_420_OPAQUE:
    case DXGI_FORMAT_NV11:
        return 12;

    case DXGI_FORMAT_R8_TYPELESS:
    case DXGI_FORMAT_R8_UNORM:
    case DXGI_FORMAT_R8_UINT:
    case DXGI_FORMAT_R8_SNORM:
    case DXGI_FORMAT_R8_SINT:
    case DXGI_FORMAT_A8_UNORM:
    case DXGI_FORMAT_AI44:
    case DXGI_FORMAT_IA44:
    case DXGI_FORMAT_P8:
    case XBOX_DXGI_FORMAT_R4G4_UNORM:
        return 8;

    case DXGI_FORMAT_R1_UNORM:
        return 1;

    case DXGI_FORMAT_BC1_TYPELESS:
    case DXGI_FORMAT_BC1_UNORM:
    case DXGI_FORMAT_BC1_UNORM_SRGB:
    case DXGI_FORMAT_BC4_TYPELESS:
    case DXGI_FORMAT_BC4_UNORM:
    case DXGI_FORMAT_BC4_SNORM:
        return 4;

    case DXGI_FORMAT_BC2_TYPELESS:
    case DXGI_FORMAT_BC2_UNORM:
    case DXGI_FORMAT_BC2_UNORM_SRGB:
    case DXGI_FORMAT_BC3_TYPELESS:
    case DXGI_FORMAT_BC3_UNORM:
    case DXGI_FORMAT_BC3_UNORM_SRGB:
    case DXGI_FORMAT_BC5_TYPELESS:
    case DXGI_FORMAT_BC5_UNORM:
    case DXGI_FORMAT_BC5_SNORM:
    case DXGI_FORMAT_BC6H_TYPELESS:
    case DXGI_FORMAT_BC6H_UF16:
    case DXGI_FORMAT_BC6H_SF16:
    case DXGI_FORMAT_BC7_TYPELESS:
    case DXGI_FORMAT_BC7_UNORM:
    case DXGI_FORMAT_BC7_UNORM_SRGB:
        return 8;

    default:
        return 0;
    }
}

当然，真正的问题是你为什么需要它？

Answer 2

您可以简单地使用switch语句创建一个函数：

int getBPP(DXGI_FORMAT format)
{
    switch(format)
    {
    case DXGI_FORMAT_R16G16B16A16_UNORM: return 16*4;
    case DXGI_FORMAT_R32G32B32A32_FLOAT: return 32*4;
    //...
    }
}

或者，您可以依赖这样一个事实，即格式通常是按其BPP分组的。严格地说，这不是真的--例如，有多组32bpp格式，但这可以通过附加条件来处理。例如：

int getBPP(DXGI_FORMAT format)
{
    //...
    else if (format >= DXGI_FORMAT_R32_TYPELESS &&
             format <= DXGI_FORMAT_X24_TYPELESS_G8_UINT)
    {
        return 32;
    }
    else if (format >= DXGI_FORMAT_R9G9B9E5_SHAREDEXP &&
             format <= DXGI_FORMAT_G8R8_G8B8_UNORM)
    {
        return 32;
    }
    //...
}

当然，这依赖于这样一个假设：DXGI_FORMAT枚举不会改变和破坏这个约定(尽管，这是非常不可能的)。

Answer 3

没有实用程序来执行转换，大多数3d引擎只是用一个基本的大开关实现自己的引擎。此外，您所列出的值也是错误的，除非您考虑的是每个组件位而不是整个像素。

int DxgiFormat2Bpp( DXGI_FORMAT fmt ) {
  switch(fmt) {
  // many cases
  case DXGI_FORMAT_R16G16B16A16_UNORM : return 64;
  case DXGI_FORMAT_R32G32B32A32_FLOAT : return 128;
  default: return -1;
  }
}