opencv 基本操作

获取图像像素值

1. 获取灰度图像像素值

   cv::Mat map = cv::imread("../asset/grid_map/1.png", cv::IMREAD_GRAYSCALE);
   //row是行数，col是列数
   int  ve_stat = map.ptr<uchar>(row)[col];
   

   dst.at<uchar>(iy, ix) = 255;
   

2. 获取RGB图像像素值

   image.at<Vec3b>(row, col)[0] = 0;
   

缩放操作

1. resize

   cv::resize(image, image_dst, cv::Size(w, h));
   

形态学处理

1. 膨胀
2. 腐蚀
3. 开操作
4. 闭操作

利用上述操作提取水平和垂直线条：

#include "stdafx.h"
#include 
#include 
using namespace cv;
using namespace std;
 
int main()
{
 Mat src, dst;
 src = imread("D:/images/1.png");
 if (src.empty())
 {
 cout << "your image is null,please check your path" << endl;
 return -1;
 }
 char INPUT_WIN[] = "input image";
 char OUTPUT_WIN[] = "result image";
 namedWindow(INPUT_WIN, CV_WINDOW_AUTOSIZE);
 imshow(INPUT_WIN, src);
 
 //输出灰色图像
 Mat gray_src;
 cvtColor(src, gray_src, CV_BGR2GRAY);
 imshow("gray image", gray_src);
 
 //装换成二值图像
 Mat binImg;
 adaptiveThreshold(~gray_src, binImg, 255,
 ADAPTIVE_THRESH_MEAN_C, THRESH_BINARY,15, -2);
 imshow("binary image", binImg);
 
 //水平结构元素
 Mat hline = getStructuringElement(MORPH_RECT, Size(src.cols / 16, 1),
 Point(-1, -1));
 //垂直结构元素
 Mat vline = getStructuringElement(MORPH_RECT,Size(1,src.rows/16),
 Point(-1, -1));
 // 矩形结构
 Mat kernel = getStructuringElement(MORPH_RECT, Size(3, 3),
 Point(-1, -1));
 
 //Mat temp;
 //erode(binImg, temp, kernel);
 //dilate(temp,dst,kernel);
 morphologyEx(binImg, dst, CV_MOP_OPEN, hline); //上面等价这个一句话
 bitwise_not(dst, dst);//值取反 255 - SrcPixel
 imshow("Final Result", dst);
 
 waitKey(0);
 return 0;
}

最小包围旋转矩形框

#include 
#include 
#include 
 
using namespace std;
using namespace cv;
 
int main()
{
	cv::Mat src = imread("test.png",0);
	cv::Mat result = src.clone();
	cv::Mat th1;
	// 最大类间差法，也称大津算法
	threshold(result, th1, 0, 255, THRESH_OTSU);
	// 反相
	th1 = 255 - th1;
	// 确定连通区轮廓
	std::vector<std::vector<cv::Point> > contours;  // 创建轮廓容器
	std::vector<cv::Vec4i> 	hierarchy;
	cv::findContours(th1, contours, hierarchy, cv::RETR_EXTERNAL, cv::CHAIN_APPROX_NONE, cv::Point());
	// 遍历轮廓显示矩形框
	for (int i = 0; i < contours.size(); ++i)
	{
		cv::RotatedRect rotatedrect = cv::minAreaRect(cv::Mat(contours[i]));
		// 存储旋转矩形的四个点
		cv::Point2f ps[4];
		rotatedrect.points(ps);
		std::vector<std::vector<cv::Point>> tmpContours;    // 创建一个InputArrayOfArrays 类型的点集
		std::vector<cv::Point> contour;
		for (int i = 0; i != 4; ++i) {
			contour.emplace_back(cv::Point2i(ps[i]));
		}
		// 插入到轮廓容器中
		tmpContours.insert(tmpContours.end(), contour);
		// 绘制轮廓，也就是绘制旋转矩形
		drawContours(result, tmpContours, -1, Scalar(0), 1, 16);  // 填充mask
	}
 
	imshow("original", src);
	imshow("thresh", th1);
	imshow("result", result);
	waitKey(0);
 
	return 0;
}