function GetNumColors: LongInt;
var
   BPP: Integer;
   DC: HDC;
begin
   DC := CreateDC('DISPLAY', nil, nil, nil);
   if DC <> 0 then begin
      try
	 BPP := GetDeviceCaps(DC, BITPIXEL) * GetDeviceCaps(DC, PLANES);
      finally
         DeleteDC(DC);
      end;
      case BPP of
         1: Result := 2;
         4: Result := 16;
         8: Result := 256;
         15: Result := 32768;
         16: Result := 65536;
         24: Result := 16777216;
      end;
   end else
      Result := 0;
end;