初识Opencv4.X----Mat类

1、Mat类

//Mat的常见构造方法
#include 
#include 
#include 
#include 
using namespace std;
using namespace cv;

int main()
{
	//Mat类的构造
	Mat a = cv::Mat::Mat();//a的属性由所赋的值决定
	a = (cv::Mat_<int>(3, 2) << 1, 2, 3, 4, 5, 6);
	Mat b = cv::Mat::Mat(3, 2, CV_8UC1);//指定行数和列数构造单通道的3x2矩阵
	Mat c = cv::Mat::Mat(Size(3, 2), CV_8UC1);//指定行数和列数构造单通道的2x3矩阵，注意与上面语句相反
	Mat d = cv::Mat::Mat(c);//通过已有Mat对象构造一个新的Mat对象,c和d的指向内容一样
	Mat e = d.clone();//通过复制构造一个新的Mat对象,d和e的指向内容不一样
	/*
	@param rowRange Range of the m rows to take.As usual, the range start is inclusive and the range
		end is exclusive.Use Range::all() to take all the rows.
	@param colRange Range of the m columns to take.Use Range::all() to take all the columns.
	这两个注释是对应cv::Mat::Mat(a, Range(0, 2), Range(0, 2))中Range(0, 2), Range(0, 2)，说明这样写就是取0~1行和0~1列
	*/
	Mat f = cv::Mat::Mat(a, Range(0, 2), Range(0, 2));//通过已有Mat对象构造一个Mat子对象
	cout << "a:" << endl << a << endl;
	cout << "b:" << endl << b << endl;
	cout << "c:" << endl << c << endl;
	cout << "d:" << endl << d << endl;
	cout << "e:" << endl << e << endl;
	cout << "f:" << endl << f << endl;
	return 0;
}

//Mat类的常见赋值
#include 
#include 
#include 
#include 
using namespace std;
using namespace cv;

int main()
{
	//Mat类的赋值
	Mat a, b, c;
	a = b = c = cv::Mat::Mat();
	b = (cv::Mat_<int>(3, 2) << 1, 2, 3, 4, 5, 6);//枚举赋值法，必须加括号，不然VS2017会报错
	c = cv::Mat::Mat(2, 2, CV_8UC3, cv::Scalar(0, 0, 255));//3通道矩阵，每个像素的三个通道值都是0, 0, 255
	//循环赋值法
	Mat d = cv::Mat_<int>(3, 3);
	for (int i = 0; i < d.rows; i++)
	{
		for (int j = 0; j < d.cols; j++)
		{
			d.at<int>(i, j) = 1;
		}
	}
	Mat e = cv::Mat::Mat::zeros(2, 2, CV_8UC1);//类方法赋值
	float m_array[8] = { 1,2,3,4,5,6,7,8 };
	Mat f = cv::Mat(2, 2, CV_32FC2, m_array);//利用数组赋值
	cout << "a:" << endl << a << endl;
	cout << "b:" << endl << b << endl;
	cout << "c:" << endl << c << endl;
	cout << "d:" << endl << d << endl;
	cout << "e:" << endl << e << endl;
	cout << "f:" << endl << f << endl;
	return 0;
}

//Mat类的运算
#include 
#include 
#include 
#include 
using namespace std;
using namespace cv;

int main()
{
	//Mat类的运算
	Mat a, b, c;
	a = (cv::Mat_<float>(3, 3) << 1, 1, 1, 1, 1, 1, 1, 1, 1);
	b = (cv::Mat_<float>(3, 3) << 1, 1, 1, 1, 1, 1, 1, 1, 1);
	c = (cv::Mat_<float>(3, 3) << 1, 1, 1, 1, 1, 1, 1, 1, 1);
	cout << "加法:" << endl;
	cout << a << "+" << endl << b << "=" << endl << a + b << endl;
	cout << "减法:" << endl;
	cout << a << "-" << endl << b << "=" << endl << a - b << endl;
	cout << "数乘:" << endl;
	cout << a << "*" << endl << 2 << "=" << endl << a * 2 << endl;
	cout << "除法:" << endl;
	cout << a << "/" << endl << 2 << "=" << endl << a / 2 << endl;
	cout << "内积:" << endl;
	cout << a << "*" << endl << c << "=" << endl << a.dot(c) << endl;
	cout << "点乘:" << endl;
	cout << a << ".*" << endl << b << "=" << endl << a.mul(b) << endl;
	return 0;
}

//Mat类元素的读取
#include 
#include 
#include 
#include 
using namespace std;
using namespace cv;

int main()
{
	//Mat类元素的读取
	//1、通过at方法读取
	Mat a = cv::Mat(3, 3, CV_8UC3, Scalar(1,1,1));
	cv::Vec3b b = a.at<Vec3b>(0, 0);//Vec3b对应uchar类型
	cout << "a[0,0]=" << b << endl;
	//2、通过指针读取
	uchar* ptr;
	for (int i = 0; i < a.rows; i++)
	{
		ptr = a.ptr<uchar>(i);
		for (int j = 0; j < a.cols*a.channels(); j++)//注意列数循环要乘上通道数
		{
			cout << (int)ptr[j] << " ";//注意要转换为int类型
		}
		cout << endl;
	}
	//3、通过迭代器
	//我不会迭代器
	//4、通过地址
	//int c = (int)(*(a.data + a.step[0]*row + a.step[1]*col + channel));
	cv::Mat d(3, 3, CV_8UC3, Scalar(0, 1, 2));
	int c = (int)(*(d.data + d.step[0] * 0 + d.step[1] * 0 + 0));
	cout << "d[0,0,1]=" << c << endl;
	c = (int)(*(d.data + d.step[0] * 0 + d.step[1] * 0 + 1));
	cout << "d[0,0,2]=" << c << endl;
	c = (int)(*(d.data + d.step[0] * 0 + d.step[1] * 0 + 2));
	cout << "d[0,0,3]=" << c << endl;
	return 0;
}

对于一些定义有疑问的地方，其实通过VS2017看源码是较好的方法