opencv之mat元素访问

• 单通道mat元素访问：使用 img.at<float>(row,col)

#include <stdlib.h>
#include <stdio.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <opencv2/opencv.hpp>

using namespace std;
using namespace cv;
int main()
{
    Mat img(3, 4, CV_32FC1, Scalar_<float>(12.625));
    
    cout<<img<<endl;
    cout<<endl;
    /*cout << "dims:" << img.dims << endl;   
    cout << "rows:" << img.rows << endl;   
    cout << "cols:" << img.cols << endl;   
    cout << "channels:" << img.channels() << endl;
    
    cout << "elemSize:" << img.elemSize() << endl;  
    cout << "elemSize1:" << img.elemSize1() << endl;*/

    

    //元素的遍历：
    for(int row = 0; row < img.rows; row++)
    {
        for(int col = 0;col < img.cols; col++)
        {
            cout<<img.at<float>(row,col)<<" ";
        }
        cout<<endl;
    }
    
    system("pause");
    return 0;
}

备注1：创建图像Mat时候可以用到

 Mat img(3, 4, CV_32FC1, Scalar_<float>(12.625));
3乘4的图片~
Mat_<uchar>对应的是CV_8U，
Mat_<char>对应的是CV_8S，
Mat_<int>对应的是CV_32S，
Mat_<float>对应的是CV_32F，
Mat_<double>对应的是CV_64F，对应的数据深度如下：

Scalar_<**>的**处填上对应的类型！！

 CV_8U - 8-bit unsigned integers ( 0..255 )
 CV_8S - 8-bit signed integers ( -128..127 )
 CV_16U - 16-bit unsigned integers ( 0..65535 )
 CV_16S - 16-bit signed integers ( -32768..32767 )
 CV_32S - 32-bit signed integers ( -2147483648..2147483647 )
 CV_32F - 32-bit ?oating-point numbers ( -FLT_MAX..FLT_MAX, INF, NAN )
 CV_64F - 64-bit ?oating-point numbers ( -DBL_MAX..DBL_MAX, INF, NAN )

备注2

因为单通道，所以上例访问元素时候对应写成

img.at<float>(row,col)

...

• 多通道mat元素访问：

#include <stdlib.h>
#include <stdio.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <opencv2/opencv.hpp>

using namespace std;
using namespace cv;
int main()
{
    Mat img(3, 4, CV_64FC2, Scalar_<double>(12.625,3.141592653));
    //Mat_(Vec)
    cout<<img<<endl;
    cout<<endl;
    /*cout << "dims:" << img.dims << endl;   
    cout << "rows:" << img.rows << endl;   
    cout << "cols:" << img.cols << endl;   
    cout << "channels:" << img.channels() << endl;
    
    cout << "elemSize:" << img.elemSize() << endl;  
    cout << "elemSize1:" << img.elemSize1() << endl;*/


    //元素的遍历：
    for(int row = 0; row < img.rows; row++)
    {
        for(int col = 0;col < img.cols; col++)
        {
            cout<<img.at<Vec2d>(row,col)[0]<<" "<<img.at<Vec2d>(row,col)[1]<<"	";
        }
        cout<<endl;
    }


    system("pause");
    return 0;
}

备注3：创建图像Mat时候，注意点同上~

备注4：使用at时img.at<**>(row,col)的**处对应选项~

typedef Vec<uchar, 2> Vec2b;
typedef Vec<uchar, 3> Vec3b;
typedef Vec<uchar, 4> Vec4b;

typedef Vec<short, 2> Vec2s;
typedef Vec<short, 3> Vec3s;
typedef Vec<short, 4> Vec4s;

typedef Vec<ushort, 2> Vec2w;
typedef Vec<ushort, 3> Vec3w;
typedef Vec<ushort, 4> Vec4w;

typedef Vec<int, 2> Vec2i;
typedef Vec<int, 3> Vec3i;
typedef Vec<int, 4> Vec4i;
typedef Vec<int, 6> Vec6i;
typedef Vec<int, 8> Vec8i;

typedef Vec<float, 2> Vec2f;
typedef Vec<float, 3> Vec3f;
typedef Vec<float, 4> Vec4f;
typedef Vec<float, 6> Vec6f;

typedef Vec<double, 2> Vec2d;
typedef Vec<double, 3> Vec3d;
typedef Vec<double, 4> Vec4d;
typedef Vec<double, 6> Vec6d;

 题外话：

我一次Mat img(3,4,CV8S,~)....而访问时候，用的img.at<int>(i,j)出现访存错误，我的本意是用CV32S，不对应就会出现访存错误。。。