Variable Dds.Header.DDPF.a_bit_mask

Alpha mask for reading alpha data. dwFlags must include DDPF_ALPHAPIXELS or DDPF_ALPHA. For instance, given the A8R8G8B8 format, the alpha mask would be 0xff000000.

struct Dds.Header.DDPF
{
  // ...
  uint a_bit_mask ;
  // ...
}