Opencv学习笔记2--像素的访问

#include "opencv2\opencv.hpp"
#include iostream
![成员函数at用来读取像素，image.at<Vec3b>(i,j)[channel] = value;
at方法不会进行类型转换，所以需要制定图像元素类型，并且要和矩阵内类型一致![这里写图片描述](https://img-blog.youkuaiyun.com/20170414140455673?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvcXEzODUxMDU1MDE=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast)
](https://img-blog.youkuaiyun.com/20170414140307218?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvcXEzODUxMDU1MDE=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast)
using namespace cv;
using namespace std;
void main()
{
（1）动态地址访问
Mat img = imread("1.jpg");
imshow("src", img);
Mat dst = img.clone();
int rowNumber = img.rows;
int colNumber = img.cols;
for (int i = 0; i < rowNumber; i++)
{
for (int j = 0; j < colNumber;j++)
{
dst.at<Vec3b>(i, j)[0] = 255;//蓝色通道
dst.at<Vec3b>(i, j)[1] = 0;//绿色通道
dst.at<Vec3b>(i, j)[2] = 0;//红色通道
}
}
imshow("dst", dst);
waitKey(0);
（2）指针访问
/*Mat img = imread("1.jpg");
imshow("src", img);
Mat dst = img.clone();
int rowNumber = img.rows;
int colNumber = img.cols*img.channels();//获取每一行的元素
for (int i = 0; i < rowNumber; i++)
{
uchar *data = dst.ptr<uchar>(i);//获取每一行的首地址
for (int j = 0; j < colNumber; j++)
{
switch (j%3)
{
case 0: //蓝色通道
data[j] = data[j]/64*64+64/2;
break;
case 1: //绿
data[j] = data[j]/64*64+32;
break;
case 2: //红
data[j] = data[j]/64*64+32;
break;
}
}
}
imshow("dst", dst);
waitKey(0);
（3）迭代器访问
Mat img = imread("1.jpg");
Mat dst = img.clone();
imshow("src", img);
Mat_<Vec3b>::iterator it = dst.begin<Vec3b>(); //初始位置
Mat_<Vec3b>::iterator itend = dst.end<Vec3b>(); //终止位置
for (; it != itend; it++)
{
(*it)[0] = 0; //蓝色通道
(*it)[1] = 255; //绿色通道
(*it)[2] = 0; //红色通道
}
imshow("dst", dst);
waitKey(0);
destroyAllWindows();
}
速度：指针>迭代器>动态地址