IWiaItem2::GetExtension method
Gets the extension interfaces that might come with a Windows Image Acquisition (WIA) 2.0 device driver.
Syntax
HRESULT GetExtension(
[in] LONG lFlags,
[in] BSTR bstrName,
[in] REFIID riidExtensionInterface,
[out] VOID **ppOut
);
Parameters
-
lFlags [in]
-
Type: LONG
Currently unused. Should be set to zero.
-
bstrName [in]
-
Type: BSTR
Specifies the name of the extension that the calling application requires a pointer to.
-
SegmentationFilter
-
The segmentation filter extension. This is currently the only valid value for this parameter.
riidExtensionInterface [in]
Type: REFIID
Specifies the identifier of the extension interface.
ppOut [out]
Type: VOID**
Receives the address of a pointer to the extension interface.
Return value
Type: HRESULT
If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.
Remarks
An application invokes this method to create an extension object implementing one of the WIA 2.0 driver extension interfaces. IWiaItem2::GetExtension stores the address of the extension object's extension interface in the riidExtensionInterface parameter. The application then uses the interface pointer to call its methods.
Applications must call the IUnknown::Release method on the interface pointers they receive through the riidExtensionInterface parameter.
Examples
CreateSegmentationFilter creates an instance of the driver's segmentation filter (IWiaSegmentationFilter) by calling IWiaItem2::GetExtension on the passed-in IWiaItem2 interface.
HRESULT
CreateSegmentationFilter(
IWiaItem2 *pWiaItem2,
IWiaSegmentationFilter **ppSegmentationFilter)
{
HRESULT hr = S_OK;
IWiaSegmentationFilter *pSegFilter = NULL;
if (!pWiaItem2 || !ppSegmentationFilter)
{
hr = E_INVALIDARG;
}
if (SUCCEEDED(hr))
{
BSTR bstrFilterString = SysAllocString(WIA_SEGMENTATION_FILTER_STR);
if (bstrFilterString)
{
hr = pWiaItem2->GetExtension(0,
bstrFilterString,
IID_IWiaSegmentationFilter,
(void**)&pSegFilter);
SysFreeString(bstrFilterString);
bstrFilterString = NULL;
}
else
{
hr = E_OUTOFMEMORY;
}
}
if (SUCCEEDED(hr))
{
*ppSegmentationFilter = pSegFilter;
pSegFilter = NULL;
}
return hr;
}
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows Vista [desktop apps only] |
| Minimum supported server |
Windows Server 2008 [desktop apps only] |
| Header |
|
| IDL |
|