Convert DXGI_FORMAT to a bpp - directx

Question

How can you convert a DXGI_FORMAT to a bpp (bit per pixel) value without enumeration? (see formats)
e.g.:
DXGI_FORMAT_R10G10B10A2_UNORM -> 32
DXGI_FORMAT_B5G5R5A1_UNORM -> 16

Answer 1

DirectXTex implements this utility function, and I have it internally in DirectX Tool Kit for DDSTextureLoader.
//-------------------------------------------------------------------------------------
// 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;
}
}
Of course, the real question is why do you need it?

Answer 2

You can simply create a function with switch statement:
int getBPP(DXGI_FORMAT format)
{
switch(format)
{
case DXGI_FORMAT_R16G16B16A16_UNORM: return 16*4;
case DXGI_FORMAT_R32G32B32A32_FLOAT: return 32*4;
//...
}
}
Alternatively, you could rely on the fact that the formats generally are grouped by their BPP. This is not strictly true - for example, there are multiple groups of 32bpp formats, but this could be handled with additional conditionals. For example:
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;
}
//...
}
This of course relies on the assumption that the DXGI_FORMAT enum won't change and break this convention (although, that's pretty unlikely).

Answer 3

There is no utilities to perform the conversion for you, most 3d engine just implement their own with a basic large switch case. Also, the value you list are wrong, unless you consider the per component bits and not the whole pixel.
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;
}
}