Opencv之像素值的获取

　　灰度图像${ m{M}} imes { m{N}}$的像素矩阵值为0~255，像素值越大越亮。${{ m{I}}_{{ m{i}}{ m{j}}}}$,i表示行的位置，j 表示列的位置即i行j列。RGB图像在Opencv中内存顺序为：BGR三个通道。

获取像素的方式有三种：代码如下

#include<opencv2/opencv.hpp>
#include<iostream>

using namespace std;
using namespace cv;
void point(Mat& inputImage, Mat& result, int div);//指针方式
void iteraton_operate(Mat& inputImage, Mat& result, int div);//迭代器方式
void dynamic_address(Mat& inputImage, Mat& result, int div);//动态地址方式
Mat src, gray, dst;
int main(int argc, char** argv)
{
    
    src = imread("H:/cv_code/image/home.jpg");
    if (src.empty())
    {
        printf("could not find image");
        return -1;
    }
    namedWindow("input");
    imshow("input",src);
    cvtColor(src,gray,COLOR_BGR2GRAY);
    namedWindow("result");
    point(src, dst, 32);
    iteraton_operate(src, dst, 32);
    dynamic_address(src, dst, 32);
    waitKey(0);
    return 0;
}
void point(Mat& inputImage, Mat& result, int div)
{
    result = inputImage.clone();
    int channels = result.channels();
    int rows = result.rows;
    int cols = result.cols * channels;
    for (int i = 0; i < rows; i++)
    {
        uchar* value = result.ptr<uchar>(i);
        for (int j = 0; j < cols; j++)
        {
            value[j] = value[j] / div * div + div / 2;
        }
    }
}
void iteraton_operate(Mat& inputImage, Mat& result, int div)
{
    result = inputImage.clone();
    Mat_<Vec3b>::iterator itbegin = result.begin<Vec3b>();
    Mat_<Vec3b>::iterator itend = result.end<Vec3b>();
    for (;itbegin !=itend;++itbegin)
    {
        (*itbegin)[0] = (*itbegin)[0] / div * div + div / 2;
        (*itbegin)[1] = (*itbegin)[1] / div * div + div / 2;
        (*itbegin)[2] = (*itbegin)[2] / div * div + div / 2;

    }

}
void dynamic_address(Mat& inputImage, Mat& result, int div)
{
    result = inputImage.clone();
    int rows = result.rows;
    int cols = result.cols;
    for (int i = 0; i < rows; i++)
    {
        
        for (int j = 0; j < cols; j++)
        {
            result.at<Vec3b>(i, j)[0] = result.at<Vec3b>(i, j)[0] / div * div + div / 2;
            result.at<Vec3b>(i, j)[1] = result.at<Vec3b>(i, j)[1] / div * div + div / 2;
            result.at<Vec3b>(i, j)[2] = result.at<Vec3b>(i, j)[2] / div * div + div / 2;
        }
    }
}