opencv-从图像旋转学习Mat数据訪问

先看一个简单的样例

代码：

// ConsoleApplication3_6_23.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<opencv2/opencv.hpp>
#include<iostream>
#include<vector>
using namespace std;
using namespace cv;

int _tmain(int argc, _TCHAR* argv[])
{
	Mat src,dst,dst1,dst2;
	src = imread("test.png");
	if(!src.data)
		return -1;
	namedWindow("原图",CV_WINDOW_AUTOSIZE);
	namedWindow("x--",CV_WINDOW_AUTOSIZE);
	namedWindow("y--",CV_WINDOW_AUTOSIZE);
	imshow("原图",src);
	int nr = src.rows;
	int nc = src.cols;
	/************************************************************************/
	/* x方向                                                                     */
	/************************************************************************/
	dst = src.clone();
	for (int i = 0;i < nr;++i)
	{
		for (int j = 0;j < nc;++j)
		{
			dst.at<Vec3b>(i,j) = src.at<Vec3b>(i,nc-j-1);
		}
	}
	imshow("x--",dst);
	/************************************************************************/
	/* y方向                                                                     */
	/************************************************************************/
	src.copyTo(dst1);
	for (int i = 0;i < nr;++i)
	{
		for (int j = 0;j < nc;++j)
		{
			dst1.at<Vec3b>(i,j) = src.at<Vec3b>(nr-i-1,j);
		}
	}
	imshow("y--",dst1);
	waitKey(0);
	return 0;
}

1、Mat的ptr和[]

void image_rever(Mat& src,Mat& dst)
{
	int nr = src.rows;
	int nc = src.cols;
	int ch = src.channels();
	for (int i = 0;i < nr;++i)
	{
		uchar* srcr = src.ptr<uchar>(i);
		uchar* dstr = dst.ptr<uchar>(i);
		for (int j = 0;j < nc;++j)
		{
			dstr[ch * j + 0] = srcr[ch * (nc - j - 1) + 0];
			dstr[ch * j + 1] = srcr[ch * (nc - j - 1) + 1];
			dstr[ch * j + 2] = srcr[ch * (nc - j - 1) + 2];
		}
	}
}

2、Mat的ptr和指针

void image_rever(Mat& src,Mat& dst)
{
	int nr = src.rows;
	int nc = src.cols;
	int ch = src.channels();
	for (int i = 0;i < nr;++i)
	{
		uchar* srcr = src.ptr<uchar>(i);
		uchar* dstr = dst.ptr<uchar>(i);
		for (int j = 0;j < nc;++j)
		{

			*(dstr + ch * j + 0) = *(srcr + (ch * (nc - j - 1) + 0));
			*(dstr + ch * j + 1) = *(srcr + (ch * (nc - j - 1) + 1));
			*(dstr + ch * j + 2) = *(srcr + (ch * (nc - j - 1) + 2));
		}
	}
}

3、Mat的迭代器iterator

void image_rever(Mat& src,Mat& dst)
{
	typedef cv::Mat_<cv::Vec3b>::iterator matIterator;
	matIterator	db = dst.begin<cv::Vec3b>();
	matIterator de = dst.end<cv::Vec3b>();

	matIterator se = src.end<cv::Vec3b>() - 1;
	for (; db != de; ++db,--se)
	{
		*db = *se;
	}
}

void image_rever(Mat& src,Mat& dst)
{
	typedef cv::Mat_<cv::Vec3b>::iterator matIterator;
	matIterator	db = dst.begin<cv::Vec3b>();
	matIterator de = dst.end<cv::Vec3b>();

	matIterator se = src.end<cv::Vec3b>() - 1;
	for (; db != de; ++db,--se)
	{
		(*db)[0] = 255 - (*se)[0];
		(*db)[1] = 255 - (*se)[1];
		(*db)[2] = 255 - (*se)[2];
	}
}