创建Mat

#include<opencv2/opencv.hpp>  
#include<iostream>  
#include<cassert>  
#include<vector>  
#include<stdio.h>
#include <sys/time.h>

using namespace cv;  
using namespace std;  

double abtic() 
{  
    double result = 0.0;  
    struct timeval tv;  
    gettimeofday(&tv, NULL);  
    result = tv.tv_sec*1000*1000 + tv.tv_usec;  
    return result;  
}

int main(int argc, char** argv)
{
    double time = 0.0;
    Mat srcImage=imread(argv[1], CV_LOAD_IMAGE_COLOR);  
    Mat B;
    Mat C;

    B = Mat(srcImage);
    printf("B-data address:%p
", B.data);
    printf("srcImage-data address:%p
", srcImage.data);

    B.copyTo(C);//deep copy
    printf("C-data address:%p
", C.data);

    Mat D(B);
    printf("D-data address:%p
", D.data);

    Mat E;
    E = B.clone();//deep copy
    printf("E-data address:%p
", E.data);

    Mat F = Mat_<uchar>(B);//same Mat(m)
    printf("F-data address:%p
", F.data);
    //Mat G = Mat_<int>(B);//datatype is different,cat not work

    time = abtic();
    Mat G; 
    B.convertTo(G, CV_64FC3);//矩阵元素数据类型的转换
    cout << "time(ms):" << (abtic()-time)/1000 << endl;
    printf("G-data address:%p
", G.data);
    cout << "G.channels:" << G.channels() << endl;
    cout << G.at<Vec3d>(1,1)[0] << endl;
    cout << G.at<Vec3d>(1,1)[1] << endl;
    cout << G.at<Vec3d>(1,1)[2] << endl;
    cout << "G.size:" << G.total() << endl;
    cout << "G.rows:" << G.rows << endl;
    cout << "G.cols:" << G.cols << endl;

    Mat H = Mat_<double>(G);//多通道强转单通道，列数会增加，即高度不变，宽度变为原来的3倍
    printf("H-data address:%p
", H.data);
    cout << "H.channels:" << H.channels() << endl;
    cout << H.at<double>(1,1) << endl;
    cout << "H.size:" << H.total() << endl;
    cout << "H.rows:" << H.rows << endl;
    cout << "H.cols:" << H.cols << endl;
    
    //result print:
    //B-data address:0x7ff653b2c020
    //srcImage-data address:0x7ff653b2c020
    //C-data address:0x7ff653a6b020
    //D-data address:0x7ff653b2c020
    //E-data address:0x7ff645b6b020
    //F-data address:0x7ff653b2c020
    //G-data address:0x7ff64556a020
    //H-data address:0x7ff64556a020
    
    return 0;
}

Mat::clone

Creates a full copy of the array and the underlying data.

C++: Mat Mat::clone() const

The method creates a full copy of the array. The original step[] is not taken into account. So, the array copy is a continuous array occupying total()*elemSize() bytes.

inline Mat Mat::clone() const
{
    Mat m;
    copyTo(m);
    return m;
}

Mat::copyTo

Copies the matrix to another one.

C++: void Mat::copyTo(OutputArray m) const

C++: void Mat::copyTo(OutputArray m, InputArray mask) const

Parameters:	m – Destination matrix. If it does not have a proper size or type before the operation, it is reallocated. mask – Operation mask. Its non-zero elements indicate which matrix elements need to be copied.

The method copies the matrix data to another matrix. Before copying the data, the method invokes

m.create(this->size(), this->type());

so that the destination matrix is reallocated if needed. While m.copyTo(m); works flawlessly, the function does not handle the case of a partial overlap between the source and the destination matrices.

When the operation mask is specified, if the Mat::create call shown above reallocates the matrix, the newly allocated matrix is initialized with all zeros before copying the data.

Mat::convertTo

Converts an array to another data type with optional scaling.

C++: void Mat::convertTo(OutputArray m, int rtype, double alpha=1, double beta=0 ) const

Parameters:	m – output matrix; if it does not have a proper size or type before the operation, it is reallocated. rtype – desired output matrix type or, rather, the depth since the number of channels are the same as the input has; if rtype is negative, the output matrix will have the same type as the input. alpha – optional scale factor. beta – optional delta added to the scaled values.

The method converts source pixel values to the target data type. saturate_cast<> is applied at the end to avoid possible overflows:

　　　　　　　　m(x,y)=saturate_case<rType>(a(*this)(x,y)+b)