Jedi：需要 GUID_DEVINTERFACE_IMAGE 的价值：TGUID

Question

早上好，

我想要获取计算机中网络摄像头的总数，并翻译在 C++ 中找到的源代码（code is here) 到 Delphi，如下所示：

 const
      MAX_PATH = 260;
      CR_SUCCESS =[=11=]000000;
    type
      HDevInfo  = Pointer; { a pointer to a HID device info structure }
      THDEVINFO = Pointer;
      PSP_DevInfo_Data = ^TSP_DevInfo_Data;
      SP_DEVINFO_DATA = packed record
        cbSize: DWORD;
        ClassGuid: TGUID;
        DevInst: DWORD;
        Reserved: LongWord;
      end;
      TSP_DevInfo_Data = SP_DEVINFO_DATA;
      PDEVPROPKEY = ^TDEVPROPKEY;
      DEVPROPKEY = packed record
        fmtid : TGUID ;
        pid : Pointer;
      end;
      TDEVPROPKEY = DEVPROPKEY;
      DEVPROPTYPE = Pointer;
      PCWSTR = PWCHAR;
      TDEVINST = DWord;
      TPOSVERSIONINFOW = ^TOSVERSIONINFOW;
      TOSVERSIONINFOW = packed record
        dwOSVersionInfoSize : DWORD ;
        dwMajorVersion : DWORD ;
        dwMinorVersion : DWORD ;
        dwBuildNumber : DWORD ;
        dwPlatformId : DWORD ;
        szCSDVersion : array[0..127] of wchar;
      end;
    function SetupDiGetDeviceProperty(DeviceInfoSet: THDEVINFO; DeviceInfoData: PSP_DEVINFO_DATA; const PropertyKey: PDEVPROPKEY; var PropertyType:DEVPROPTYPE; PropertyBuffer:PBYTE;PropertyBufferSize:DWORD; RequiredSize:PDWORD; Flags:DWORD): BOOL; stdcall; external 'Setupapi.DLL' name 'SetupDiGetDevicePropertyW';
    function SetupDiGetClassDevsW(const ClassGuid: PGUID; Enumerator: PCWSTR; hwndParent: HWND; Flags: DWORD): THDEVINFO; stdcall; external 'Setupapi.DLL' name 'SetupDiGetClassDevsW';
    function SetupDiGetClassDevsA(ClassGuid: PGUID; const Enumerator: PAnsiChar;
hwndParent: HWND; Flags: DWORD): THandle; stdcall; external 'SetupApi.dll';
    function SetupDiEnumDeviceInfo(DeviceInfoSet: THDEVINFO; MemberIndex: DWORD; DeviceInfoData: PSP_DEVINFO_DATA): BOOL; stdcall; external 'Setupapi.DLL' name 'SetupDiEnumDeviceInfo';
    function CM_Get_Device_IDW(DeviceInstanceHandle: TDEVINst; Buffer:PCWSTR; Bufferlen : ULONG; ulFlags:ULONG): DWORD; stdcall; external 'Setupapi.DLL' name 'CM_Get_Device_IDW';
    function SetupDiGetDeviceRegistryPropertyW(DeviceInfoSet: THDEVINFO; const DeviceInfoData: SP_DevInfo_Data; Property_: DWORD; var PropertyRegDataType: DWORD; PropertyBuffer: PBYTE; PropertyBufferSize: DWORD; var RequiredSize: DWORD): BOOL; stdcall; external 'Setupapi.DLL' name 'SetupDiGetDeviceRegistryPropertyW';
    function GetVersionExW(OsVersion:TPOSVERSIONINFOW): BOOL; stdcall; external 'Kernel32.dll' name 'GetVersionExW';

    const
            DIGCF_PRESENT = [=11=]000002;
            DIGCF_ALLCLASSES = [=11=]000004;
            DIGCF_PROFILE = [=11=]000008;
            DIGCF_DEVICEINTERFACE = [=11=]000010;
            INVALID_HANDLE_VALUE = DWORD($FFFFFFFF);
            MAX_DEVICE_ID_LEN = 200;
            SPDRP_DEVICEDESC = ([=11=]000000) ;
            DEVPKEY_Device_BusReportedDeviceDesc : TDEVPROPKEY = (fmtid : '{540b947e-8b40-45bc-a8a2-6a0b894cbda2}' ; pid : pointer(4) );

implementation

        function GetNumCam: integer;
        var
        MemberIndex: integer;
        dev: HDEVINFO;
        DeviceInfoData: SP_DEVINFO_DATA;
        begin
        DeviceInfoData.cbSize := sizeof(DeviceInfoData);
        dev := SetupDiGetClassDevsA(@GUID_DEVINTERFACE_IMAGE, nil, nil, DIGCF_PRESENT);
         if dev = nil then  begin
         //raise exception.Create('Nenhum dispositivo encontrado');
         exit;
         end
         else
           while SetupDiEnumDeviceInfo(dev,MemberIndex, @DeviceInfoData) do
           begin
            MemberIndex:= MemberIndex + 1;
           end;
        Result:= MemberIndex;
        end;

但是我很难在 Delphi 中找到 GUID_DEVINTERFACE_IMAGE 的值，然后为这个常量分配这个值。我在 (this unit) 中看到，但没有这个常量，因为我抓住了价值。

有人知道这个常量的确切值吗？

提前致谢。

Answer 1

可以在documentation中找到该值：

{0x6bdd1fc6L, 0x810f, 0x11d0, 0xbe, 0xc7, 0x08, 0x00, 0x2b, 0xe2, 0x09, 0x2f}

在 Delphi 中，您可以这样声明：

const
  GUID_DEVINTERFACE_IMAGE: TGUID = (
    D1:bdd1fc6; D2:0f; D3:d0; D4:($be, $c7, , [=10=], b, $e2, , f)
  );

或者像这样：

const
  GUID_DEVINTERFACE_IMAGE: TGUID = '{6bdd1fc6-810f-11d0-bec7-08002be2092f}';

Jedi：需要 GUID_DEVINTERFACE_IMAGE 的价值：TGUID

Jedi: Needing of value for GUID_DEVINTERFACE_IMAGE: TGUID

delphi