Re: Create a CBitmap from SAFEARRAY

On 14 Mar 2007 08:43:17 -0700, dom_perron@hotmail.com wrote:


Hi,

sorry, but I don't know how to mix C++ and .NET stuff.

(Frankly speaking, if I want to use .NET, I would use C# - a well
designed language - and not what I consider an ugly "genetic-modified"
:) C++ with managed .NET extensions: the so called "managed C++".

And if I need communication between .NET managed world and native
Win32 world, I would use simple C-interface DLLs or COM interop.
But it's just IMHO.)

However, if you have a pointer to the SAFEARRAY, and you want to use
its data, this is how you might consider to do:

<CODE>

// SAFEARRAY * psa;

HRESULT hr;
BYTE * pBytes = NULL;

// Get a pointer to the elements of the array
hr = SafeArrayAccessData( psa, (void HUGEP**)&pBytes );
if (FAILED(hr))
  // Error ...

// *** Use the data pointed by pBytes ***

....
....

// Release array
SafeArrayUnaccessData( psa );
pBytes = NULL;

</CODE>

If your byte array is just a memory copy of a bitmap file, you may
consider using the following function to create the bitmap from this
data.

It's just:

HBITMAP hbmpMyImage = LoadBitmapFromMemory( pBytes );

(The routine uses ::CreateDIBSection.)

Here's the code:

<CODE>

//------------------------------------------------------------------
// Load a DIB file from memory buffer.
// Return bitmap handle on success, NULL on error
//
// by MrAsm
//------------------------------------------------------------------
HBITMAP LoadBitmapFromMemory( void * pBmpFileData )
{
    // Check parameter
    ASSERT( pBmpFileData != NULL );
    if ( pBmpFileData == NULL )
        return NULL;

    // Pointer to file bytes
    BYTE * pFileBytes = (BYTE *)pBmpFileData;

    // DIB bits (will be set by CreateDIBSection)
    BYTE * pBits = NULL;

    // Access the BITMAPINFOHEADER section
    BITMAPINFOHEADER * pbmih = (BITMAPINFOHEADER *)(pFileBytes +
                                  sizeof(BITMAPFILEHEADER));

    // Create the DIB
    HBITMAP hBitmap = ::CreateDIBSection(
        NULL, // No HDC used
        (BITMAPINFO *)pbmih, // Pointer to DIB information
        0, // Default
        (void **)&pBits, // The function will return pointer to
                                // bitmap bits
        NULL, // No file mapping
        0 ); // No file mapping
    if ( hBitmap == NULL )
        return NULL;

    // Get pointer to bitmap bits in original file
    // (we obtain the offset from BITMAPFILEHEADER.bfOffBits field)
    BITMAPFILEHEADER * pbmfh = (BITMAPFILEHEADER *)pFileBytes;
    BYTE * pSourceBitmapBits = pFileBytes + pbmfh->bfOffBits;

    // Copy bits
    memcpy(pBits, pSourceBitmapBits, pbmih->biSizeImage);

    // Return bitmap handle
    return hBitmap;
}

</CODE>

Hope it helps,
MrAsm