WIA，无法枚举本机系统中的扫描仪

HRESULT CreateWiaDeviceManager(IWiaDevMgr2 **ppWiaDevMgr) //Vista or later

{

	//

	// Validate arguments

	//

	if (NULL == ppWiaDevMgr)

	{

		return E_INVALIDARG;

	}



	//

	// Initialize out variables

	//

	*ppWiaDevMgr = NULL;



	//

	// Create an instance of the device manager

	//



	//XP or earlier:

	//HRESULT hr = CoCreateInstance(CLSID_WiaDevMgr, NULL, CLSCTX_LOCAL_SERVER, IID_IWiaDevMgr, (void**)ppWiaDevMgr);



	//Vista or later:

	HRESULT hr = CoCreateInstance(CLSID_WiaDevMgr2, NULL, CLSCTX_LOCAL_SERVER, IID_IWiaDevMgr2, (void**)ppWiaDevMgr);



	//

	// Return the result of creating the device manager

	//

	return hr;

}



HRESULT EnumerateWiaDevices(IWiaDevMgr2 *pWiaDevMgr) //Vista or later

{

	//

	// Validate arguments

	//

	if (NULL == pWiaDevMgr)

	{

		return E_INVALIDARG;

	}



	//

	// Get a device enumerator interface

	//

	IEnumWIA_DEV_INFO *pWiaEnumDevInfo = NULL;

	HRESULT hr = pWiaDevMgr->EnumDeviceInfo(WIA_DEVINFO_ENUM_LOCAL, &pWiaEnumDevInfo);

	if (SUCCEEDED(hr))

	{

		//

		// Loop until you get an error or pWiaEnumDevInfo->Next returns

		// S_FALSE to signal the end of the list.

		//

		while (S_OK == hr)

		{



			u_long dicount = 0;

			hr = pWiaEnumDevInfo->GetCount(&dicount);

                        //此处hr返回s_ok，但dicount为0，但我电脑上确实连接了一个扫描仪，驱动也装好了，可以正常使用

			//

			// Get the next device's property storage interface pointer

			//

			IWiaPropertyStorage *pWiaPropertyStorage = NULL;

			hr = pWiaEnumDevInfo->Next(1, &pWiaPropertyStorage, NULL);

                        //这里直接返回S_FAILED

			//

			// pWiaEnumDevInfo->Next will return S_FALSE when the list is

			// exhausted, so check for S_OK before using the returned

			// value.

			//

			if (hr == S_OK)

			{

				//

				// Do something with the device's IWiaPropertyStorage*

				//



				PROPSPEC PropSpec[3] = { 0 };

				PROPVARIANT PropVar[3] = { 0 };

				

				const u_long propcount = sizeof(PROPSPEC) / sizeof(PropSpec[0]);



				//

				// Define which properties you want to read:

				// Device ID.  This is what you would use to create

				// the device.

				//

				PropSpec[0].ulKind = PRSPEC_PROPID;

				PropSpec[0].propid = WIA_DIP_DEV_ID;



				//

				// Device Name

				//

				PropSpec[1].ulKind = PRSPEC_PROPID;

				PropSpec[1].propid = WIA_DIP_DEV_NAME;



				//

				// Device description

				//

				PropSpec[2].ulKind = PRSPEC_PROPID;

				PropSpec[2].propid = WIA_DIP_DEV_DESC;





				hr = pWiaPropertyStorage->ReadMultiple(propcount, PropSpec, PropVar);

				if (SUCCEEDED(hr))

				{

					//

					// IWiaPropertyStorage::ReadMultiple will return S_FALSE if some

					// properties could not be read, so you have to check the return

					// types for each requested item.

					//



					//

					// Check the return type for the device ID

					//

					if (VT_BSTR == PropVar[0].vt)

					{

						//

						// Do something with the device ID

						//

						_tprintf(TEXT("WIA_DIP_DEV_ID: %ws\n"), PropVar[0].bstrVal);

					}



					//

					// Check the return type for the device name

					//

					if (VT_BSTR == PropVar[1].vt)

					{

						//

						// Do something with the device name

						//

						_tprintf(TEXT("WIA_DIP_DEV_NAME: %ws\n"), PropVar[1].bstrVal);

					}



					//

					// Check the return type for the device description

					//

					if (VT_BSTR == PropVar[2].vt)

					{

						//

						// Do something with the device description

						//

						_tprintf(TEXT("WIA_DIP_DEV_DESC: %ws\n"), PropVar[2].bstrVal);

					}



					//

					// Free the returned PROPVARIANTs

					//

					FreePropVariantArray(propcount, PropVar);



				}



				//

				// Release the device's IWiaPropertyStorage*

				//

				pWiaPropertyStorage->Release();

				pWiaPropertyStorage = NULL;

			}

		}



		//

		// If the result of the enumeration is S_FALSE (which

		// is normal), change it to S_OK.

		//

		if (S_FALSE == hr)

		{

			hr = S_OK;

		}



		//

		// Release the enumerator

		//

		pWiaEnumDevInfo->Release();

		pWiaEnumDevInfo = NULL;

	}



	//

	// Return the result of the enumeration

	//

	return hr;

}









int main()

{

	CoInitialize(NULL);

	IWiaDevMgr2 *pWait;

	HRESULT hr = CreateWiaDeviceManager(&pWait);

	if (hr != S_OK)

	{

		_tprintf(_T("create devicemanager error %d"), GetLastError());

		CoUninitialize();

		return -1;

	}



	EnumerateWiaDevices(pWait);

	getchar();

	pWait->Release();

	CoUninitialize();

	return 0;

}