CImage::Load() from memory without using CreateStreamOnHGlobal

问题

I am displaying a live view video from camera. Every frame I download into a byte array (pImageData) which I have to allocate.

Now, to display, I am using a CImage (MFC). However, all samples I find are based on using GlobalAlloc, yet another memcpy and CreateStreamOnHGlobal.

I'd like to avoid doing another allocation/deallocation and memory copy. Each frame is over 2mb and I am pushing 30 fps!

Is it possible to create an IStream on non-HGLOBAL based memory? OR Is it somehow possible to coerce Image::Load() to work with byte array?

Here is the code:

// pImageData is an array with bytes, size is the sizeOfThatArray

CComPtr<IStream> stream;

HGLOBAL hMem = ::GlobalAlloc(GHND, size);
LPVOID pBuff = ::GlobalLock(hMem);

memcpy(pBuff, pImageData, size); // <-- would like to avoid this

::GlobalUnlock(hMem);

CreateStreamOnHGlobal(hMem, TRUE, &stream); // <-- or create stream on non-hglobal memory

CImage image;
image.Load(stream); // <-- Or load directly from pImageData

// .. display image

image.Destroy();

::GlobalFree(hMem);

回答1:

Thanks to Hans for pointing out SHCreateMemStream, which I did not know existed. The code is much cleaner, but still unsure whether SHCreateMemStream creates a copy internally (documentation is unclear)

[edit] As per Jonathan' comments, looks like it still has to make a copy internally. Dang ..

Final code

// pImageData is an array with bytes, size is the sizeOfThatArray

// Still not clear if this is making a copy internally
IStream* pMemStream = SHCreateMemStream(pImageData, size);

CComPtr<IStream> stream;

stream.Attach(pMemStream); // Need to Attach, otherwise ownership is not transferred and we leak memory

CImage image;
image.Load(stream); 

// .. display image

image.Destroy();

// No need for further cleanup, CComPtr does the job

来源：https://stackoverflow.com/questions/38691416/cimageload-from-memory-without-using-createstreamonhglobal