java opencv Mat 面积 opencv中mat的用法

在《OpenCV Mat主要用法(1)》主要是详细分析了Mat类中的主要Method用法，可以了解到Mat中常用的创建，访问，变量等一些方法，但是有时候还远远不够。OpenCV Mat主要功能就是将图片信息统一保存到Mat 矩阵中，使之能够按照矩阵的方式进行各种算法的演进，但实际上Mat存储方式为矩阵，为了使用方便就应该提供各种常见的加减乘除矩阵式操作方式，如果每次让开发人员来自己实现两个矩阵的加减乘除操作，想想就是非常可怕。OpenCV提供了各种常见的数学表达式操作。

Mat是如何实现常见表达式操作

Mat实现常见表达式操作，是通过operator=重构来实现的，在《OpenCV Mat主要用法(1)》中Mat对operator=重构中有两个API，其中有一个重要的API:

在API中有详细的说明 expr为支持常见的Mat 矩阵表达式，Mat是通过MatExpr类来实现常见的表达式。每次写Mat表达式时就相当于调用到了operator=重构函数，最后调用到了MatExpr类。OpenCV通过这种设计方式将其API与表达式进行了功能上完美隔离。在《Learning OpenCV3》:第四章“Images and Large Array Types”中的Matrix Expression:Algebra and cv:Mat部分中有明确的提到，感兴趣的读者可以读下原著。下面摘自其部分原话：

The result of the computation is finally placed in the destination array by operator=().However,  one important distinction is that this form of operator=() is not assigning a cv::Mat or a cv::Mat(as it might appear),but rather a cv::MatExpr(the expression itself) to a cv::mat.

Mat支持的常见的矩阵表达式

Mat支持的常见表达式如下：

Example	Description
m0 + m1, m0-m1	m0, m1为两个Mat矩阵，支持两个矩阵相加或相减 m0中相对应的矩阵位置值与m1中相对应的矩阵位置值相加或相减
m0+ s；m0-s; s+mo; s-m1;	s为离散值，支持离散值与矩阵向加或相减，此时矩阵中每个值都相加或相减同一个s值
-m0	支持对矩阵中的每个值取符号相反
s*m0;m0*s	矩阵乘以一个s常数
m0.mul(m1); m0/m1	支持两个矩阵每个值相乘或相除
m0*m1	矩阵相乘
m0.inv(method)	支持矩阵的逆
m0.t()	支持矩阵转置
m0>m1;m0>=m1;m0 == m1; m0<=m1; m0<m1	支持两个矩阵比较，比较的结果为0或者255

下面为几个简单例子：

两个矩阵相加或相减用例：

#include <stdio.h>
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace cv;
using namespace std;


void main()
{
	Mat A(3, 3, CV_32FC1);
	Mat B(3, 3, CV_32FC1);
	
	A.at<float>(0, 0) = 1;
	A.at<float>(0, 1) = 2;
	A.at<float>(0, 2) = 3;
	A.at<float>(1, 0) = 4;
	A.at<float>(1, 1) = 5;
	A.at<float>(1, 2) = 6;
	A.at<float>(2, 0) = 1;
	A.at<float>(2, 1) = 2;
	A.at<float>(2, 2) = 3;


	B.at<float>(0, 0) = 3;
	B.at<float>(0, 1) = 2;
	B.at<float>(0, 2) = 1;
	B.at<float>(1, 0) = 6;
	B.at<float>(1, 1) = 5;
	B.at<float>(1, 2) = 4;
	B.at<float>(2, 0) = 1;
	B.at<float>(2, 1) = 2;
	B.at<float>(2, 2) = 3;
	cout << "A = "<<endl<<  A<< endl;
	cout << "B= "  <<endl<< B << endl;
	cout << "A+B = "  <<endl<< A+B << endl;
	cout << "A-B = " << endl << A - B << endl;

}

运行结果：

常量与矩阵相加减用例：

 

#include <stdio.h>
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace cv;
using namespace std;


void main()
{
	Mat A(3, 3, CV_32FC1);
	Mat B(3, 3, CV_32FC1);
	
	A.at<float>(0, 0) = 1;
	A.at<float>(0, 1) = 2;
	A.at<float>(0, 2) = 3;
	A.at<float>(1, 0) = 4;
	A.at<float>(1, 1) = 5;
	A.at<float>(1, 2) = 6;
	A.at<float>(2, 0) = 1;
	A.at<float>(2, 1) = 2;
	A.at<float>(2, 2) = 3;


	B.at<float>(0, 0) = 3;
	B.at<float>(0, 1) = 2;
	B.at<float>(0, 2) = 1;
	B.at<float>(1, 0) = 6;
	B.at<float>(1, 1) = 5;
	B.at<float>(1, 2) = 4;
	B.at<float>(2, 0) = 1;

	B.at<float>(2, 1) = 2;
	B.at<float>(2, 2) = 3;
	cout << "A = "<<endl<<  A<< endl;
	cout << "B= "  <<endl<< B << endl;
	cout << "A+B = "  <<endl<< A+2 << endl;
	cout << "A-B = " << endl << A - 2 << endl;

}

运行结果：

 

 矩阵符号取反：

#include <stdio.h>
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace cv;
using namespace std;


void main()
{
	Mat A(3, 3, CV_32FC1);
	Mat B(3, 3, CV_32FC1);
	
	A.at<float>(0, 0) = 1;
	A.at<float>(0, 1) = 2;
	A.at<float>(0, 2) = 3;
	A.at<float>(1, 0) = 4;
	A.at<float>(1, 1) = 5;
	A.at<float>(1, 2) = 6;
	A.at<float>(2, 0) = 1;
	A.at<float>(2, 1) = 2;
	A.at<float>(2, 2) = 3;


	B.at<float>(0, 0) = 3;
	B.at<float>(0, 1) = 2;
	B.at<float>(0, 2) = 1;
	B.at<float>(1, 0) = 6;
	B.at<float>(1, 1) = 5;
	B.at<float>(1, 2) = 4;
	B.at<float>(2, 0) = 1;

	B.at<float>(2, 1) = 2;
	B.at<float>(2, 2) = 3;
	cout << "A = "<<endl<<  A<< endl;
	cout << "B= "  <<endl<< B << endl;
	cout << "-A = "  <<endl<< -A << endl;
	cout << "-B= " << endl << -B << endl;

}

运行结果：

矩阵相乘或相除：

 

#include <stdio.h>
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace cv;
using namespace std;


void main()
{
	Mat A(3, 3, CV_32FC1);
	Mat B(3, 3, CV_32FC1);
	
	A.at<float>(0, 0) = 1;
	A.at<float>(0, 1) = 2;
	A.at<float>(0, 2) = 3;
	A.at<float>(1, 0) = 4;
	A.at<float>(1, 1) = 5;
	A.at<float>(1, 2) = 6;
	A.at<float>(2, 0) = 1;
	A.at<float>(2, 1) = 2;
	A.at<float>(2, 2) = 3;


	B.at<float>(0, 0) = 3;
	B.at<float>(0, 1) = 2;
	B.at<float>(0, 2) = 1;
	B.at<float>(1, 0) = 6;
	B.at<float>(1, 1) = 5;
	B.at<float>(1, 2) = 4;
	B.at<float>(2, 0) = 1;

	B.at<float>(2, 1) = 2;
	B.at<float>(2, 2) = 3;
	cout << "A = "<<endl<<  A<< endl;
	cout << "B= "  <<endl<< B << endl;
	cout << "A.mul(B) = "  <<endl<< A.mul(B)<< endl;
	cout << "A/B " << endl << A/B<< endl;

}

运行结果：

 

 矩阵乘以或者除以一个常数：

#include <stdio.h>
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace cv;
using namespace std;


void main()
{
	Mat A(3, 3, CV_32FC1);
	Mat B(3, 3, CV_32FC1);
	
	A.at<float>(0, 0) = 1;
	A.at<float>(0, 1) = 2;
	A.at<float>(0, 2) = 3;
	A.at<float>(1, 0) = 4;
	A.at<float>(1, 1) = 5;
	A.at<float>(1, 2) = 6;
	A.at<float>(2, 0) = 1;
	A.at<float>(2, 1) = 2;
	A.at<float>(2, 2) = 3;


	B.at<float>(0, 0) = 3;
	B.at<float>(0, 1) = 2;
	B.at<float>(0, 2) = 1;
	B.at<float>(1, 0) = 6;
	B.at<float>(1, 1) = 5;
	B.at<float>(1, 2) = 4;
	B.at<float>(2, 0) = 1;

	B.at<float>(2, 1) = 2;
	B.at<float>(2, 2) = 3;
	cout << "A = "<<endl<<  A<< endl;
	cout << "B= "  <<endl<< B << endl;
	cout << "A*2 = "  <<endl<< A*2<< endl;
	cout << "B/2 " << endl << B/2<< endl;

}

运行结果：

 两个矩阵比较

#include <stdio.h>
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

using namespace cv;
using namespace std;


void main()
{
	Mat A(3, 3, CV_32FC1);
	Mat B(3, 3, CV_32FC1);
	
	A.at<float>(0, 0) = 1;
	A.at<float>(0, 1) = 2;
	A.at<float>(0, 2) = 3;
	A.at<float>(1, 0) = 4;
	A.at<float>(1, 1) = 5;
	A.at<float>(1, 2) = 6;
	A.at<float>(2, 0) = 1;
	A.at<float>(2, 1) = 2;
	A.at<float>(2, 2) = 3;


	B.at<float>(0, 0) = 3;
	B.at<float>(0, 1) = 2;
	B.at<float>(0, 2) = 1;
	B.at<float>(1, 0) = 6;
	B.at<float>(1, 1) = 5;
	B.at<float>(1, 2) = 4;
	B.at<float>(2, 0) = 1;

	B.at<float>(2, 1) = 2;
	B.at<float>(2, 2) = 3;
	cout << "A = "<<endl<<  A<< endl;
	cout << "B= "  <<endl<< B << endl;
	cout << "A>=B "  <<endl<< (A>=B)<< endl;
	

}

运行结果：

MatExpr类

由上述分析可知，mat的矩阵表达式是通过MatExpr类来实现的 ，而MatExpr类中大部分的实现基本上都是通过C++的operator特性，通过对常用表达式重构来实现的，可以查看MatExpr类都重构了哪些常用的操作符

operator	Method
+ 加	CV_EXPORTS MatExpr operator + (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator + (const Mat& a, const Scalar& s)
	CV_EXPORTS MatExpr operator + (const Scalar& s, const Mat& a)
	CV_EXPORTS MatExpr operator + (const MatExpr& e, const Mat& m)
	CV_EXPORTS MatExpr operator + (const Mat& m, const MatExpr& e)
	CV_EXPORTS MatExpr operator + (const MatExpr& e, const Scalar& s)
	CV_EXPORTS MatExpr operator + (const Scalar& s, const MatExpr& e)
	CV_EXPORTS MatExpr operator + (const MatExpr& e1, const MatExpr& e2)
	template<typename _Tp, int m, int n> static inline MatExpr operator + (const Mat& a, const Matx<_Tp, m, n>& b
	template<typename _Tp, int m, int n> static inline MatExpr operator + (const Matx<_Tp, m, n>& a, const Mat& b)
-减	CV_EXPORTS MatExpr operator - (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator - (const Mat& a, const Scalar& s)
	CV_EXPORTS MatExpr operator - (const Scalar& s, const Mat& a)
	CV_EXPORTS MatExpr operator - (const MatExpr& e, const Mat& m)
	CV_EXPORTS MatExpr operator - (const Mat& m, const MatExpr& e)
	CV_EXPORTS MatExpr operator - (const MatExpr& e, const Scalar& s)
	CV_EXPORTS MatExpr operator - (const Scalar& s, const MatExpr& e)
	CV_EXPORTS MatExpr operator - (const MatExpr& e1, const MatExpr& e2)
	template<typename _Tp, int m, int n> static inline MatExpr operator - (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator - (const Matx<_Tp, m, n>& a, const Mat& b)
	CV_EXPORTS MatExpr operator - (const Mat& m)
	CV_EXPORTS MatExpr operator - (const MatExpr& e)
*乘 注意：如果是两个矩阵，则做的是两个矩阵相乘，如果要两个矩阵每个对应位置的元素相乘则使用mul函数接口	CV_EXPORTS MatExpr operator * (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator * (const Mat& a, double s)
	CV_EXPORTS MatExpr operator * (double s, const Mat& a)
	CV_EXPORTS MatExpr operator * (const MatExpr& e, const Mat& m)
	CV_EXPORTS MatExpr operator * (const Mat& m, const MatExpr& e)
	CV_EXPORTS MatExpr operator * (const MatExpr& e, double s)
	CV_EXPORTS MatExpr operator * (double s, const MatExpr& e)
	CV_EXPORTS MatExpr operator * (const MatExpr& e1, const MatExpr& e2)
	template<typename _Tp, int m, int n> static inline MatExpr operator * (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator * (const Matx<_Tp, m, n>& a, const Mat& b)
/：除	CV_EXPORTS MatExpr operator / (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator / (const Mat& a, double s)
	CV_EXPORTS MatExpr operator / (double s, const Mat& a)
	CV_EXPORTS MatExpr operator / (const MatExpr& e, const Mat& m)
	CV_EXPORTS MatExpr operator / (const Mat& m, const MatExpr& e)
	CV_EXPORTS MatExpr operator / (const MatExpr& e, double s)
	CV_EXPORTS MatExpr operator / (double s, const MatExpr& e)
	CV_EXPORTS MatExpr operator / (const MatExpr& e1, const MatExpr& e2)
	template<typename _Tp, int m, int n> static inline MatExpr operator / (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator / (const Matx<_Tp, m, n>& a, const Mat& b)
<:小于	CV_EXPORTS MatExpr operator < (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator < (const Mat& a, double s)
	CV_EXPORTS MatExpr operator < (double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator < (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator < (const Matx<_Tp, m, n>& a, const Mat& b)
<=:小于等于	CV_EXPORTS MatExpr operator <= (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator <= (const Mat& a, double s)
	CV_EXPORTS MatExpr operator <= (double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator <= (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator <= (const Matx<_Tp, m, n>& a, const Mat& b)
==：等于	CV_EXPORTS MatExpr operator == (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator == (const Mat& a, double s)
	CV_EXPORTS MatExpr operator == (double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator == (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator == (const Matx<_Tp, m, n>& a, const Mat& b)
！=:不等于	CV_EXPORTS MatExpr operator != (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator != (const Mat& a, double s)
	CV_EXPORTS MatExpr operator != (double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator != (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator != (const Matx<_Tp, m, n>& a, const Mat& b)
>=:大于等于	CV_EXPORTS MatExpr operator >= (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator >= (const Mat& a, double s)
	CV_EXPORTS MatExpr operator >= (double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator >= (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator >= (const Matx<_Tp, m, n>& a, const Mat& b)
>:大于	CV_EXPORTS MatExpr operator > (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator > (const Mat& a, double s)
	CV_EXPORTS MatExpr operator > (double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator > (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator > (const Matx<_Tp, m, n>& a, const Mat& b)
&：与操作	CV_EXPORTS MatExpr operator & (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator & (const Mat& a, const Scalar& s)
	CV_EXPORTS MatExpr operator & (const Scalar& s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator & (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator & (const Matx<_Tp, m, n>& a, const Mat& b)
|：或操作	CV_EXPORTS MatExpr operator | (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator | (const Mat& a, const Scalar& s)
	CV_EXPORTS MatExpr operator | (const Scalar& s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator | (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator | (const Matx<_Tp, m, n>& a, const Mat& b)
^：异或	CV_EXPORTS MatExpr operator ^ (const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr operator ^ (const Mat& a, const Scalar& s)
	CV_EXPORTS MatExpr operator ^ (const Scalar& s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr operator ^ (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr operator ^ (const Matx<_Tp, m, n>& a, const Mat& b)
~:取反	CV_EXPORTS MatExpr operator ~(const Mat& m)
min:取两者最小值	CV_EXPORTS MatExpr min(const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr min(const Mat& a, double s)
	CV_EXPORTS MatExpr min(double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr min (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr min (const Matx<_Tp, m, n>& a, const Mat& b)
max:两者最大值	CV_EXPORTS MatExpr max(const Mat& a, const Mat& b)
	CV_EXPORTS MatExpr max(const Mat& a, double s)
	CV_EXPORTS MatExpr max(double s, const Mat& a)
	template<typename _Tp, int m, int n> static inline MatExpr max (const Mat& a, const Matx<_Tp, m, n>& b)
	template<typename _Tp, int m, int n> static inline MatExpr max (const Matx<_Tp, m, n>& a, const Mat& b)
abs:两者差的绝对值	CV_EXPORTS MatExpr abs(const Mat& m)
	CV_EXPORTS MatExpr abs(const MatExpr& e)
t	MatExpr t()
inv	MatExpr inv(int method = DECOMP_LU)
mul	MatExpr mul(const Mat& m, double scale=1)
cross	Mat cross(const Mat& m)
dot	double dot(const Mat& m)