Using CImage.Save (InMemory) - c++

Question

I'm working with some pictures in a MFC application, and I realized that the CImage class (from MFC) has 2 types of save, to a file and to a IStream interface. I'm trying to use that IStream interface to save to memory, using the convention features of the CImage class without another library to do that (for example bmp to jpg convertion). I don't want to save a file, just work with the memory buffers. The CImage object is already loaded with a picture file.
But I'm not able to use this IStream interface because I cannot create a object from that class and not realized how to create the buffer to use with that Save(IStream * pStream...) feature.
Any example will be very helpful.
Thanks,
Vitor

Answer 1

First, you should add your picture to a resource id, and to do like this:
BOOL ImageFromIDResource(UINT nID, LPCTSTR sTR, CImage * & pImg)
{
HINSTANCE hInst = AfxGetResourceHandle();
HRSRC hRsrc = ::FindResource(hInst, MAKEINTRESOURCE(nID), sTR); // type
if (!hRsrc)
return FALSE;
// load resource into memory
DWORD len = SizeofResource(hInst, hRsrc);
BYTE* lpRsrc = (BYTE*)LoadResource(hInst, hRsrc);
if (!lpRsrc)
return FALSE;
// Allocate global memory on which to create stream
HGLOBAL m_hMem = GlobalAlloc(GMEM_FIXED, len);
BYTE* pmem = (BYTE*)GlobalLock(m_hMem);
memcpy(pmem, lpRsrc, len);
IStream* pstm = NULL;
CreateStreamOnHGlobal(m_hMem, FALSE, &pstm);
// load from stream
//pImg = Gdiplus::Image::FromStream(pstm);
pImg = new CImage();
pImg->Load(pstm);
DWORD err = GetLastError();
// free/release stuff
GlobalUnlock(m_hMem);
pstm->Release();
FreeResource(lpRsrc);
return TRUE;
}