OpenCV在循环中调整大小-内存泄漏

Question

I'm trying to resize Mats stored in vector. As a result I'd like to have all resized Mats stored in original vector. Using resize(original_mat, original_mat ....) in for loop results in memory leak. The same thing is when I use the code below - loop acts like the whole vector was copied and stored in memory.

Mat temp;
for (int i=0; i< im.size();i++){
    resize(im[i],temp,size,0,0,CV_INTER_LINEAR);
    im[i] = temp.clone();
}

Is there a way to avoid copying whole vector and allocate memory only for single Mats? Thanks in advance.

Edit: I perform a lot of operations on my input frames before resizing them (for example - downsampling), so I tried to see what happens when I resize frames form vector right after reading the video. So, I made this:

VideoCapture input_file(input_filename);
int number_of_frames = input_file.get(CV_CAP_PROP_FRAME_COUNT);
vector <Mat> im;
for (int i=0; i<number_of_frames; i++){
    Mat frame;
    bool isFrame = input_file.read(frame);
    im.push_back(frame);
    frame.release();
}
Mat temp;
for (int i=0; i< im.size();i++){
    resize(im[i],temp,Size,0,0,CV_INTER_LINEAR);
    im[i] = temp.clone();
}

Now memory leaks in first for loop, which makes my problem similar to this: out of memory when reading file (I'm also using OpenCV 3.0.0). So, I think that I'm just forced to avoid holding my whole video in a vector.

Answer 1

frame.release(); will cause problem where you are freeing the actual data of the frame. The item in the vector will contain then just a header without data.

Notice that when you push_back an item to a vector, the copy constructor of that item is called. The copy constructor of the Mat is a shallow copy not a deep copy which means that only the header will be copied and no deep copy will happen. In other words, both Mat will reference the same actual data.

There must not be any memory leak. How you know there is a memory leak? if you are using a profiler, it may be wrong. If you are watching memory using and see it increasing significantly, it is normal because you are storing a video in the memory without any encoding. Which means that each frame may be 5-6 MB with basic math : 5(MB)*30(FPS)*60(Sec)~ 9 GB per minute . So there is no memory leak, there is a huge data in the memory and they are not the same.