C++ 如何确定 cv::Mat 是否为零矩阵？
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How to determine if a cv::Mat is a zero matrix?
提问by JM92
I have a matrix that is dynamically being changed according to the following code;
我有一个根据以下代码动态更改的矩阵；
for( It=all_frames.begin(); It != all_frames.end(); ++It)
{
ItTemp = *It;
subtract(ItTemp, Base, NewData);
cout << "The size of the new data for ";
cout << " is \n" << NewData.rows << "x" << NewData.cols << endl;
cout << "The New Data is: \n" << NewData << endl << endl;
NewData_Vector.push_back(NewData.clone());
}
What I want to do is determine the frames at which the cv::Mat NewData is a zero matrix. I've tried comparing it to a zero matrix that is of the same size, using both the cv::compare() function and simple operators (i.e NewData == NoData), but I can't even compile the program.
我想要做的是确定 cv::Mat NewData 为零矩阵的帧。我尝试将它与大小相同的零矩阵进行比较，同时使用 cv::compare() 函数和简单的运算符（即 NewData == NoData），但我什至无法编译程序。
Is there a simple way of determining when a cv::Mat is populated by zeroes?
有没有一种简单的方法可以确定 cv::Mat 何时填充零？
回答by JM92
I used
我用了
if (countNonZero(NewData) < 1)
{
cout << "Eye contact occurs in this frame" << endl;
}
This is a pretty simple (if perhaps not the most elegant) way of doing it.
这是一种非常简单（如果可能不是最优雅的）的方法。
回答by tomriddle_1234
To check the mat if is empty, use empty(), if NewData is a cv::Mat, NewData.empty()returns true if there's no element in NewData.
要检查 mat 是否为空，请使用empty()，如果 NewData 是 cv::Mat，NewData.empty()如果 NewData 中没有元素，则返回 true。
To check if it's all zero, simply, NewData == Mat::zeros(NewData.size(), NewData.type()).
要检查它是否全部为零，只需，NewData == Mat::zeros(NewData.size(), NewData.type()).
Update:
更新：
After checking the OpenCV source code, you can actually do NewData == 0to check all element is equal to 0.
检查 OpenCV 源代码后，您实际上NewData == 0可以检查所有元素是否等于 0。
回答by malli
countNonZero(Mat ) will give u number of non zeros in mat
countNonZero(Mat ) 将在 mat 中给出 u 个非零值
回答by David Gatti
回答by Spaceghost
How about this..
这个怎么样..
Mat img = Mat::zeros(cvSize(1024, 1024), CV_8UC3);
bool flag = true;
MatConstIterator_<double> it = img.begin<double>();
MatConstIterator_<double> it_end = img.end<double>();
for(; it != it_end; ++it)
{
if(*it != 0)
{
flag = false;
break;
}
}
