Convert DXGI_FORMAT to a bpp

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

score 3 · Accepted Answer · answered Nov 01 '16 at 07:20

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?

I use them in a dialog window for configuring the graphics settings. — Matthias, Nov 01 '16 at 09:03

score 1 · Answer 2 · answered Nov 01 '16 at 07:13

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).

score 0 · Answer 3 · answered Oct 31 '16 at 19:46

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;
  }
}

Convert DXGI_FORMAT to a bpp

3 Answers3