Base64Encode HGLOBAL from clipboard

From:

Jeff <jeff.hillman@gmail.com>

Newsgroups:

microsoft.public.vc.atl,microsoft.public.win32.programmer.ole

Date:

Wed, 11 Jun 2008 21:08:20 -0700 (PDT)

Message-ID:

<47272150-358f-4dcb-9616-485bb12dab03@i36g2000prf.googlegroups.com>

I am trying to base64 encode some binary data stored on the
clipboard. The resulting string will be stored in an XML file. The
data is a PNG image, and the string I get from ATL::Base64Encode seems
to be very wrong. The data on the clipboard seems to be fine, and I
believe that I am retrieving it correctly, but the string has several
invalid characters at the end ("=CD=FD=FD=FD=FD=AB=AB=AB=AB=AB=AB=AB=AB=FE=
=EE=FE"), and there are no
'=' characters. Here is the code:

hr = spDataObject->GetData( &formatEtc, &stgMedium );

if ( SUCCEEDED( hr ) )
{
    if ( stgMedium.hGlobal != NULL )
    {
        BYTE *pImage = (LPBYTE)::GlobalLock( stgMedium.hGlobal ) );

        // this call works just fine, so the data appears to be valid
        std::fstream filestream( "D:\\image.png", std::ios::out |
                                                  std::ios::binary |
                                                  std::ios::app );
        filestream.write( reinterpret_cast<char *>( pImage ),
                          ::GlobalSize( stgMedium.hGlobal ) );
        filestream.close();

        if ( pImage )
        {
            int iSize = Base64EncodeGetRequiredLength(
                ::GlobalSize( stgMedium.hGlobal ),
                ATL_BASE64_FLAG_NOPAD | ATL_BASE64_FLAG_NOCRLF );

            char *szBase64Image = new char[ iSize ];

            if ( Base64Encode( pImage,
                               ::GlobalSize( stgMedium.hGlobal ),
                               szBase64Image,
                               &iSize,
                               ATL_BASE64_FLAG_NOPAD |
                               ATL_BASE64_FLAG_NOCRLF ) )
            {
                // store szBase64Image in XML...
            }

            delete [] szBase64Image;
        }

        ::GlobalUnlock( stgMedium.hGlobal );
    }

    ::ReleaseStgMedium( &stgMedium );
}

I have tried other methods for obtaining the BYTE array, including
CreateILockBytesOnHGlobal. I don't think that is the problem. I
don't have a lot of experience with the clipboard, and I have never
used ATL::Base64Encode before, so any help with what I am doing wrong
would be appreciated.

Thank you.

Jeff