使用C ++ STL而不复制数据

Question

I am using Opencv Mat container to read frames from video steam. I need both current and previous frames.

For now I am copying the current frame to the previous frame at the end of each iteration. Is it possible to avoid this deep copy using one of the STL containers?

std::string VidPath;
VideoCapture VidStream;
cv::Mat Prev,Curr;

if (!VidStream.open(VidPath))
{
    cout << "Cant open video" << endl;
    return 1;
}

VidStream.read(Prev);

while(VidStream.read(Curr))
{
   //do some operations between Curr and Prev 
   Curr.copyTo(Prev)// is it possible to avoid this copy?
}

Answer 1

Yes, this is called swapping.

One option would be to hold two pointers in your class. One is for the current frame and one for the previous frame.
When you are done processing your current frame, just swap the pointers and start working on the next frame again (which then can override the current frame).

An other option would be to use two std::vector which provide the swap method, which means no copying.
Other Container like std::list or std::dequeu also provide the swap method.

You may find additional information when searching for double buffering, which is a technique for flicker free content displaying.