我如何得到一个多维cv :: Mat的大小？ （Mat或MatND） [英] How do i get the size of a multi-dimensional cv::Mat? (Mat, or MatND)

问题描述

我创建了一个多维的MAT对象，并想获得对象的大小 - 例如

I am creating a multi-dimensional MAT object, and would like to get the size of the object - e.g.,

const int sz[] = {10,10,9};
Mat temp(3,sz,CV_64F);
std::cout << "temp.dims = " << temp.dims << " temp.size = " << temp.size() << " temp.channels = " << temp.channels() << std::endl;

我相信结果MAT为10x10x9，我想确认，但COUT语句给出：

I believe the resulting MAT to be 10x10x9, and I'd like to confirm, but the COUT statement gives:

temp.dims = 3 temp.size = [10 x 10] temp.channels = 1

temp.dims = 3 temp.size = [10 x 10] temp.channels = 1

我希望看到：

temp.dims = 3 temp.size = [10 x 10 x 9] temp.channels = 1

temp.dims = 3 temp.size = [10 x 10 x 9] temp.channels = 1

或：

temp.dims = 3 temp.size = [10 x 10] temp.channels = 9

temp.dims = 3 temp.size = [10 x 10] temp.channels = 9

如何获得这个Mat对象的维度？我在Mat :: Mat或MatND中没有看到任何方法

How can I get the dimensionality of this Mat object? I didn't see any methods in Mat::Mat or MatND

推荐答案

你刚刚发现自己是OpenCV C ++ API。

You just found yourself one of the many flaws of the OpenCV C++ API.

如果你看看OpenCV的源代码版本2.4.6.1，你会实现 cv :: Mat： ：size 是类型 cv :: Mat :: MSize 的成员对象，其定义为

If you take a look at the source code of OpenCV, version 2.4.6.1, you will realize cv::Mat::size is a member object of type cv::Mat::MSize, which is defined as

struct CV_EXPORTS MSize
{
    MSize(int* _p);
    Size operator()() const;
    const int& operator[](int i) const;
    int& operator[](int i);
    operator const int*() const;
    bool operator == (const MSize& sz) const;
    bool operator != (const MSize& sz) const;

    int* p;
};

因此 cv :: Mat :: size（）实际上是指 cv :: Mat :: MSize :: operator（）（），其返回类型 Size 定义为

Thus cv::Mat::size() actually refers to cv::Mat::MSize::operator ()(), whose return type Size is defined as

typedef Size_<int> Size2i;
typedef Size2i Size;

引用 OpenCV手册，大小是

用于指定图片或矩形大小的模板类别该类包含两个成员，名称为width和height。

换句话说， Size 只适用于2D矩阵。

In other words, Size is only suitable for 2D matrices.

幸运的是，所有希望都不会丢失，因为可以使用 cv :: Mat :: MSize :: operator []（int i）以获取矩阵沿其第i个维度的大小。

Fortunately all hope is not lost as you can use cv::Mat::MSize::operator [](int i) to get the size of the matrix along its i-th dimension.

const int sz[] = {10,10,9}; 
cv::Mat temp(3,sz,CV_64F); 
std::cout << "temp.dims = " << temp.dims << "temp.size = [";
for(int i = 0; i < temp.dims; ++i) {
    if(i) std::cout << " X ";
    std::cout << temp.size[i];
}
std::cout << "] temp.channels = " << temp.channels() << std::endl;

temp.dims = 3 temp.size = [10 x 10 x 9] temp.channels = 1

temp.dims = 3 temp.size = [10 x 10 x 9] temp.channels = 1

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