Opencv - 释放内存将cv :: Mat引用计数器更改为零

Question

可以使用此方法释放内存吗？

while(true){ 
     Mat img = imread("C:/image.jpg"); 
     img.refcount = 0; 
     img.release(); 
    } 

如果内存以这种方式释放，会发生什么情况？假设所指出的点是安全的。

Answer 1

如果你试图释放这样的内存，你将不会成功。查看源代码（请参阅下文），如果recount为NULL，则不执行解除分配。实际上，当用指向用户分配数据的指针构造Mat时，refcount被设置为NULL。

inline void Mat::release() 
{ 
    if(refcount && CV_XADD(refcount, -1) == 1) 
     deallocate(); 
    data = datastart = dataend = datalimit = 0; 
    size.p[0] = 0; 
    refcount = 0; 
} 

如果在另一方面，通过MariusSiuram的建议，你设定在零引用计数什么百分点，释放一定会成功。 但我不确定为什么你会这样做，因为img的析构函数会为您解除分配。

关于你提到的有关在矢量擦除垫评论，这里是一个演示：

#include<opencv2/core/core.hpp> 
#include "opencv2/highgui/highgui.hpp" 
#include <vector> 
#include <iostream> 
using namespace std; 

int main() 
{ 
    cv::Mat img = cv::imread("lena.jpg"); 
    cout << "*refcount = " << (*img.refcount) << " should be 1" << endl; 
    vector<cv::Mat> v; 
    v.push_back(img); 
    v.push_back(img); 
    v.push_back(img); 
    v.push_back(img); 
    cout << "*refcount = " << (*img.refcount) << " should be 5" << endl; 
    auto f = v.begin(); 
    ++f; 
    v.erase(f); 
    cout << "*refcount = " << (*img.refcount) << " should be 4" << endl; 
    f = v.end(); 
    --f; 
    v.erase(f); 
    cout << "*refcount = " << (*img.refcount) << " should be 3" << endl; 
    v.resize(0); 
    cout << "*refcount = " << (*img.refcount) << " should be 1" << endl; 
    img.release(); 
    cout << "refcount ptr = " << (img.refcount) << " should be 0" << endl; 
} 

输出的结果是：

*refcount = 1 should be 1 
*refcount = 5 should be 5 
*refcount = 4 should be 4 
*refcount = 3 should be 3 
*refcount = 1 should be 1 
refcount ptr = 00000000 should be 0