WIA 2.0, C++: IWiaDevMgr2::EnumDeviceInfo doesn't detect connected camera - c++

Question

I'm trying to write a program that transfers images and videos from a camera (for my personal use, on Win 8.1). I'm using Microsoft's example code as a starting point (WIA Tutorial), and I've hit a wall trying to detect connected camera devices. The problem is that there are no errors and the code seems to work, but it just doesn't detect any connected camera (I've tried with two different cameras), while the camera is clearly detected by the OS (shows up in Windows Explorer).
Am I missing something? Is IWiaDevMgr2::EnumDeviceInfo not the way to detect connected devices? Here's the code I'm using:
HRESULT WiaCreateDeviceManager(IWiaDevMgr2 **ppWiaDevMgr)
{
if(NULL == ppWiaDevMgr) return E_INVALIDARG;
*ppWiaDevMgr = NULL;
// Create an instance of the device manager
HRESULT hr = CoCreateInstance(CLSID_WiaDevMgr2, NULL, CLSCTX_LOCAL_SERVER, IID_IWiaDevMgr2, (void**)ppWiaDevMgr);
return hr;
}
HRESULT WiaEnumerateDevices(IWiaDevMgr2 *pWiaDevMgr)
{
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);
assert(hr == S_OK);
if(SUCCEEDED(hr))
{
ULONG count(911);
HRESULT res = pWiaEnumDevInfo->GetCount(&count);
if(res == S_OK) printf("EnumDeviceInfo: count = %lu\n", count); // count is always zero
else printf("IEnumWIA_DEV_INFO::GetCount() failed!\n");
// Loop until you get an error or pWiaEnumDevInfo->Next returns
// S_FALSE to signal the end of the list.
while(S_OK == hr)
{
// Get the next device's property storage interface pointer
IWiaPropertyStorage *pWiaPropertyStorage = NULL;
hr = pWiaEnumDevInfo->Next(1, &pWiaPropertyStorage, NULL);
// 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*
WiaReadProperties(pWiaPropertyStorage); // this line is never reached
// 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 hr;
}
int main()
{
...
IWiaDevMgr2 *wiamgr;
WiaCreateDeviceManager(&wiamgr);
HRESULT res = WiaEnumerateDevices(wiamgr); // res is always S_OK, but no device is detected
...
}

Answer 1

Apparently, WIA does not support camera devices on Windows Vista and later. I've only seen this implied or mentioned in passing twice in the WIA documentation, the last time being on this page. I can't believe this is happening, after I've spent so much time researching WIA. Apparently, I'm supposed to be using WPD for cameras, not WIA.
Edit: That being said, I'm still not sure what's going on. If I can't use WIA programmatically on Win 8.1, then why do these PowerShell commands work?
$WIAdialog = New-Object -ComObject "WIA.CommonDialog"
$Device = $WIAdialog.ShowSelectDevice()
$i=$WIAdialog.ShowAcquireImage()
$i.SaveFile("$pwd\test.$($i.fileExtension)")
Is it that only the API doesn't work for cameras, while the Scripting Model does?