如何在OpenCV中创建空Mat？ [英] How to create empty Mat in OpenCV?

问题描述

如何在OpenCV中创建空Mat？创建后我想使用push_back方法在Mat中推行。

How to create empty Mat in OpenCV? After creation I want to use push_back method to push rows in Mat.

类似：

Mat M(0,3,CV_32FC1);

或只有选项是：

Mat M;
M.converTo(M,CV_32FC1);

？

推荐答案

您可以使用下列方法创建一个空矩阵：

You can create an empty matrix simply using:

Mat m;

如果您已经知道其类型，您可以执行：

If you already know its type, you can do:

Mat1f m; // Empty matrix of float

如果知道其大小 p>

If you know its size:

Mat1f m(rows, cols);  // rows, cols are int
or 
Mat1f m(size);  // size is cv::Size

还可以添加默认值：

And you can also add the default value:

Mat1f m(2, 3, 4.1f);
//
// 4.1 4.1 4.1
// 4.1 4.1 4.1

如果您要向 push_back 的空矩阵中添加值，您可以按@berak建议的方式进行：

If you want to add values to an empty matrix with push_back, you can do as already suggested by @berak:

Mat1f m;
m.push_back(Mat1f(1, 3, 3.5f));   // The  first push back defines type and width of the matrix
m.push_back(Mat1f(1, 3, 9.1f));
m.push_back(Mat1f(1, 3, 2.7f));

// m
// 3.5 3.5 3.5
// 9.1 9.1 9.1
// 2.7 2.7 2.7 

如果你需要push_back包含在 vector<> 中的数据，并将其转置。

If you need to push_back data contained in vector<>, you should take care to put values in a matrix and transpose it.

vector<float> v1 = {1.1f, 2.2f, 3.3f, 4.4f, 5.5f};
vector<float> v2 = {1.2f, 2.3f, 3.4f, 4.5f, 5.6f};

Mat1f m1(Mat1f(v1).t());
Mat1f m2(Mat1f(v2).t());

Mat1f m;
m.push_back(m1);
m.push_back(m2);

// m
// 1.1 2.2 3.3 4.4 5.5
// 1.2 2.3 3.4 4.5 5.6

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