不使用CreateStreamOnHGlobal的情况下从内存CImage :: Load() [英] CImage::Load() from memory without using CreateStreamOnHGlobal
问题描述
我正在显示来自摄像机的实时取景视频.我将每一帧下载到必须分配的字节数组(pImageData)中.
I am displaying a live view video from camera. Every frame I download into a byte array (pImageData) which I have to allocate.
现在,要显示,我正在使用CImage(MFC). 但是,我发现的所有样本都基于使用GlobalAlloc,另一个memcpy和CreateStreamOnHGlobal.
Now, to display, I am using a CImage (MFC). However, all samples I find are based on using GlobalAlloc, yet another memcpy and CreateStreamOnHGlobal.
我想避免进行其他分配/取消分配和内存复制.每帧超过2mb,我正在推动30 fps!
I'd like to avoid doing another allocation/deallocation and memory copy. Each frame is over 2mb and I am pushing 30 fps!
是否可以在基于非HGLOBAL的内存上创建IStream? 或者 是否可以强制Image :: Load()使用字节数组?
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?
这是代码:
// 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);
推荐答案
感谢Hans指出SHCreateMemStream,我不知道它是否存在. 该代码更简洁,但仍不确定SHCreateMemStream是否在内部创建副本(文档不清楚)
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]根据乔纳森(Jonathan)的评论,看起来它仍然必须在内部进行复制.当..
[edit] As per Jonathan' comments, looks like it still has to make a copy internally. Dang ..
最终密码
// 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
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