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Transferring Image Data in WIA 2.0

Note  This tutorial demonstrates how to transfer image data in applications that run on Windows Vista or later. See Transfering Image Data in WIA 1.0 for information about transferring image data in applications that run on Windows XP or earlier.

Because image data transfer is stream-based in Windows Image Acquisition (WIA) 2.0, you do not need to specify a destination type (e.g. memory or file). The application simply gives WIA 2.0 the stream to use, and the driver reads or writes to the stream. The stream can be a file stream, a memory stream, or any other type of stream, and is transparent to the driver. Using streams also provides an easy integration with the Image Processing filter.

Use the methods of the IWiaTransfer interface to transfer data from a WIA 2.0 device to an application. This interface is available through the IWiaItem2 interface. The IWiaTransfer interface has methods for requesting uploading or downloading of data to and from a device. These methods take a callback that the application provides, and use an IStream provided by the application for the actual destination of the data transfer.

Applications must query an image item to obtain a pointer to its IWiaTransfer interface, as shown in the following code sample:


    // Get the IWiaTransfer interface
    //
    IWiaTransfer *pWiaTransfer = NULL;
    hr = pIWiaItem2->QueryInterface(IID_IWiaTransfer,(void**)&pWiaTransfer);


In the previous code, we assume that pWiaItem2 is a valid pointer to the IWiaItem2 interface. The call to IUnknown::QueryInterface fills pWiaTransfer with a pointer to the IWiaTransfer interface of the item referred to by pWiaItem2.

The application then instantiates the callback object, as shown here.


    //   Instantiate the object which receives the callbacks
    //
    CWiaTransferCallback *pWiaClassCallback = new CWiaTransferCallback;


The application next sets the properties by using IWiaPropertyStorage interface of IWiaItem2 item, and performs the transfer.

Downloading:


    // Download   
    hr = pWiaTransfer->Download(0,pWiaClassCallback);


Uploading:


    //Create child item which eventually will be the uploaded image 
    IWiaItem2* pWiaItemChild = NULL;
    HRESULT hr = pIWiaItem2->CreateChildItem(WiaItemTypeImage|WiaItemTypeFile,0,bzUploadFileName,&pWiaItemChild);
    
    if(SUCCEEDED(hr))
    {
                
        //Set the format for the child item as BMP 
        IWiaPropertyStorage* pWiaChildPropertyStorage = NULL;
        hr = pWiaItemChild->QueryInterface( IID_IWiaPropertyStorage, (void**)&pWiaChildPropertyStorage );
        if(SUCCEEDED(hr))
        {
            WritePropertyGuid(pWiaChildPropertyStorage,WIA_IPA_FORMAT,WiaImgFmt_BMP );

            //release pWiaChildPropertyStorage
            pWiaChildPropertyStorage->Release();
            pWiaChildPropertyStorage = NULL;
        }
        

        //Get the IWiaTransfer interface of the child
        IWiaTransfer* pWiaTransferChild = NULL;
        hr = pWiaItemChild->QueryInterface( IID_IWiaTransfer, (void**)&pWiaTransferChild );
        if(SUCCEEDED(hr)){
            IStream* pUploadStream = NULL;
                                        
            //Create stream on test.BMP file
            hr = SHCreateStreamOnFile(L"test.BMP",STGM_READ, &pUploadStream);
            if(SUCCEEDED(hr)){
                pWiaTransferChild->Upload(0,pUploadStream,pWiaClassCallback);
                
            }
         }
   
      }


Here is the complete data transfer sample:


HRESULT TransferWiaItem( IWiaItem2 *pIWiaItem2)
{
    // Validate arguments
    if (NULL == pIWiaItem2)
    {
        _tprintf(TEXT("\nInvalid parameters passed"));
        return E_INVALIDARG;
    }
    
    // Get the IWiaTransfer interface
    IWiaTransfer *pWiaTransfer = NULL;
    HRESULT hr = pIWiaItem2->QueryInterface( IID_IWiaTransfer, (void**)&pWiaTransfer );
    if (SUCCEEDED(hr))
    {
        // Create our callback class
        CWiaTransferCallback *pWiaClassCallback = new CWiaTransferCallback;
        if (pWiaClassCallback)
        {
            
              LONG lItemType = 0;
              hr = pIWiaItem2->GetItemType( &lItemType );

              //download all items which have WiaItemTypeTransfer flag set
              if(lItemType & WiaItemTypeTransfer)
              {

                  // If it is a folder, do folder download . Hence with one API call, all the leaf nodes of this folder 
                  // will be transferred
                  if ((lItemType & WiaItemTypeFolder))
                  {
                        _tprintf ( L"\nI am a folder item");
                        hr = pWiaTransfer->Download(WIA_TRANSFER_ACQUIRE_CHILDREN, pWiaClassCallback);
                        if(S_OK == hr)
                        {
                            _tprintf(TEXT("\npWiaTransfer->Download() on folder item SUCCEEDED"));
                        }
                        else if(S_FALSE == hr)
                        {
                            ReportError(TEXT("\npWiaTransfer->Download() on folder item returned S_FALSE. Folder may not be having child items"),hr);
                        }
                        else if(FAILED(hr))
                        {
                            ReportError(TEXT("\npWiaTransfer->Download() on folder item failed"),hr);
                        }
                   }

                  
                  // If this is an file type, do file download
                  else if (lItemType & WiaItemTypeFile )
                  {
                      hr = pWiaTransfer->Download(0,pWiaClassCallback);
                      if(S_OK == hr)
                      {
                          _tprintf(TEXT("\npWiaTransfer->Download() on file item SUCCEEDED"));
                      }
                      else if(S_FALSE == hr)
                      {
                          ReportError(TEXT("\npWiaTransfer->Download() on file item returned S_FALSE. File may be empty"),hr);
                      }
                      else if(FAILED(hr))
                      {
                         ReportError(TEXT("\npWiaTransfer->Download() on file item failed"),hr);
                      }
                  }                     
                }
                
                // Release our callback.  It should now delete itself.
                pWiaClassCallback->Release();
                pWiaClassCallback = NULL;
        }
        else
        {
            ReportError( TEXT("\nUnable to create CWiaTransferCallback class instance") );
        }
            
        // Release the IWiaTransfer
        pWiaTransfer->Release();
        pWiaTransfer = NULL;
    }
    else
    {
        ReportError( TEXT("\npIWiaItem2->QueryInterface failed on IID_IWiaTransfer"), hr );
    }
    return hr;
}

// Callback Class should be something like this:

class CWiaTransferCallback : public IWiaTransferCallback
{
public: // Constructors, destructor
    CWiaTransferCallback () : m_cRef(1) {};
    ~ CWiaTransferCallback () {};

public: // IWiaTransferCallback
    HRESULT __stdcall TransferCallback(
        LONG                lFlags,
        WiaTransferParams   *pWiaTransferParams)
    {
        HRESULT hr = S_OK;

        switch (pWiaTransferParams->lMessage)
        {
            case WIA_TRANSFER_MSG_STATUS:
                ...
                break;
            case WIA_TRANSFER_MSG_END_OF_STREAM:
                ...
                break;
            case WIA_TRANSFER_MSG_END_OF_TRANSFER:
                ...
                break;
            default:
                break;
        }

        return hr;
    }

    HRESULT __stdcall GetNextStream(
        LONG    lFlags,
        BSTR    bstrItemName,
        BSTR    bstrFullItemName,
        IStream **ppDestination)
    {

        HRESULT hr = S_OK;

        //  Return a new stream for this item's data.
        //
        hr = CreateDestinationStream(bstrItemName, ppDestination);
        return hr;
    }

public: // IUnknown
        .
        .
        . // Etc.

private:
    /// For ref counting implementation
    LONG                m_cRef;
};



 

 

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