Opencv计算机视觉编程攻略-第一节 图像读取与基本处理

1. 图像读取

导入依赖项的h文件

#include <iostream>

#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>

二 读取图片

Mat image; // 图像矩阵
std::cout << "This image is " << image.rows << " x "
	<< image.cols << std::endl;
// read the input image as a gray-scale image
image = cv::imread("E:/CODE/images/puppy.bmp", cv::IMREAD_GRAYSCALE);

cv::IMREAD_GRAYSCALE 以灰度图 ，默认是彩色图

1. Mat 常见操作

//创建Mat图像矩阵 CV_8U CV_8UC3 参数对应位数 通道数
Mat image1(240, 320, CV_8U, 100); 
//100 为默认值，三通道使用cv::Scalar(0, 0, 255)
//图像直接复制
image3.copyTo(image2);
//图像对象直接继承
Mat image4(image3);
// 图像对象格式转换
image1.convertTo(image2, CV_32F, 1 / 255.0, 0.0);
// 获取mat块某一片区域
image=  cv::imread("puppy.bmp");
// define image ROI at image bottom-right
imageROI= image(cv::Rect(image.cols-logo.cols,image.rows-logo.rows,
	                     logo.cols,logo.rows));
 // use the logo as a mask (must be gray-level)
 cv::Mat mask(logo);

// insert by copying only at locations of non-zero mask 0值区域为透明
logo.copyTo(imageROI,mask);

2. Matx 矩阵计算

	// a 3x3 matrix of double-precision
	cv::Matx33d matrix(3.0, 2.0, 1.0,
		2.0, 1.0, 3.0,
		1.0, 2.0, 3.0);
	// a 3x1 matrix (a vector)
	cv::Matx31d vector(5.0, 1.0, 3.0);
	// multiplication
	cv::Matx31d result = matrix * vector;

三 窗口响应函数

下列函数实现opencv窗口的点击事件监听

void onMouse(int event, int x, int y, int flags, void* param) {

	Mat* im = reinterpret_cast<Mat*>(param);
	switch (event) {	// dispatch the event
	case cv::EVENT_LBUTTONDOWN: // mouse button down event
	// display pixel value at (x,y)
	cout << "at (" << x << "," << y << ") value is: "
		<< static_cast<int>(im->at<uchar>(cv::Point(x, y))) << std::endl;
	break;
	}
}

将监听函数绑定到窗口

	namedWindow("Original Image"); // define the window (optional)
	imshow("Original Image", image); // show the image
	// 绑定点击事件
	setMouseCallback("Original Image", onMouse, reinterpret_cast<void*>(&image));

四 图像绘制内容

flip(image, result, 1); // 图像翻转
// 0 for vertical,                     
// negative for both
// 保存位图
imwrite("output.bmp", result); // save result

// 在image中画圆
cv::circle(image,              // destination image 
	cv::Point(155, 110), // center coordinate
	65,                 // radius  
	0,                  // color (here black)
	3);                 // thickness
// 在图像上写字
cv::putText(image,                   // destination image
	"This is a dog.",        // text
	cv::Point(40, 200),       // text position
	cv::FONT_HERSHEY_PLAIN,  // font type
	2.0,                     // font scale
	255,                     // text color (here white)
	2);                      // text thickness