Question

Code to save jpeg in disk:

fwrite( dataPosition, 1, BufferSize, hFileImage );

That code work good.
But something is wrong when I try read data to stream:

HGLOBAL hGlobal = GlobalAlloc(GMEM_FIXED, BufferSize);
CComPtr<IStream> spStream;
HRESULT hr = CreateStreamOnHGlobal(NULL, TRUE, &spStream);
ULONG pcbWritten;//don't understand what it is
spStream->Write(dataPosition, BufferSize, &pcbWritten);
pImage = new Image(spStream, FALSE);

After that it seems that stream (and pImage) is empty. I am not sure what I am doing wrong?

Answer 1

After you wrote to the stream, you perhaps should IStream::Seek the stream to its beginning so that following Image constructor could read the data, and not immediately reach end of stream instead.

static const ULONGLONG g_nZero = 0;
HRESULT nSeekResult = pStream->Seek(reinterpret_cast<const LARGE_INTEGER&>(g_nZero),
  STREAM_SEEK_SET, NULL);