OpenCV学习笔记（二）——Mat，图像的新容器

基础知识

自从版本2.0，OpenCV采用了新的数据结构，用Mat类结构取代了之前用extended C写的cvMat和lplImage，更加好用啦，最大的好处就是更加方便的进行内存管理，对写更大的程序是很好的消息。

#include<opencv2\opencv.hpp> #include <iostream> using namespace cv; using namespace std; int main(int argc,char *argv[]) { Mat image; //声明类 image = imread("lena.jpg", IMREAD_COLOR); if (!image.data){ // Check for invalid input cout << "Could not open or find the image" << std::endl; return -1; } Mat gray_image; cvtColor(image, gray_image, CV_BGR2GRAY); //将彩色图像变为灰度图像 imwrite("Gray_Image.jpg", gray_image); //write picture namedWindow("Color image", CV_WINDOW_AUTOSIZE); namedWindow("Gray image", CV_WINDOW_AUTOSIZE); imshow("Color image", image); //原图 imshow("Gray image", gray_image); //灰色 waitKey(0); return 0; }

Mat解析

1. Mat是一个类，有构造函数，赋值函数等

1 Mat A, C; // creates just the header parts 2 A = imread(argv[1], CV_LOAD_IMAGE_COLOR); // here we’ll know the method used (allocate matrix) 3 Mat B(A); // Use the copy constructor 4 C = A; // Assignment operator

2. 如果要拷贝自己的矩阵：

1 Mat F = A.clone(); 2 Mat G; 3 A.copyTo(G);

3. 构造函数解析

Mat M(2,2, CV_8UC3, Scalar(0,0,255)); cout << "M = " << endl << " " << M << endl << endl;

构造2*2的矩阵。 CV_[The number of bits per item][Signed or Unsigned][Type Prefix]C[The channel number] CV_8UC3 means we use unsigned char types that are 8 bit long and each pixel has three of these to form the three channels.

4. 与原始的转换

IplImage* img = cvLoadImage("greatwave.png", 1); Mat mtx(img); // convert IplImage* -> Mat Mat I; IplImage* pI = &I.operator IplImage(); CvMat* mI = &I.operator CvMat();

5. 改变矩阵creat()函数 不能用来初始化一个矩阵，它不是构造函数，它用来改变一个已有的矩阵的格式。

Create() function: M.create(4,4, CV_8UC(2)); cout << "M = "<< endl << " " << M << endl << endl;

6. Matlab类型初始化操作

Mat E = Mat::eye(4, 4, CV_64F); cout << "E = " << endl << " " << E << endl << endl; Mat O = Mat::ones(2, 2, CV_32F); cout << "O = " << endl << " " << O << endl << endl; Mat Z = Mat::zeros(3,3, CV_8UC1); cout << "Z = " << endl << " " << Z << endl << endl;