Opencv XML/YAML读写教程翻译

学习目标：
本文档将解决以下问题：
 如何在OpenCV中利用XML和YAML读取和打印文件？
 如何利用XML和YAML对OpenCV内建的数据结构读取和打印？
 如何利用XML和YAML对用户自定义的数据结构打印？
 学习使用OpenCV的相关数据结构，cv::FileStorage,cv::FileNode,cv::FileN

odeIterator。
源文件：
以下源文件可以在OpenCVd的官方网站上下载（其中的注释被改写为中文）。

#include<opencv2/core.hpp>#include<iostream>#include<string>using namespace std;using namespace cv;static void help(char** av){    cout<<endl        <<av[0]<<"shows the usage of the OpenCV serialization functionality." <<endl        <<"Usage:"        <<av[0]<<"outputfile.yml.gz"                                           <<endl        <<"The output file may be either XML or YAML(yml/yaml).You can even compress it "        <<"by specifying this in its extension like xml.gz yaml.gz etc..."        <<"With FileStorage you can serialize objects in OpenCV by using the << and >> operators"<<endl        <<"For example: -create a class and have it serialized"         <<endl        <<"             -use it to read and write matrices."<<endl;        // 以上是对程序的介绍，说明了可以对XML和YAML或者压缩文件打开，对自定义的类也可以使用，同时"<<"">>"        // 这两个操作符被重载 }class myData{pubic:    MyData():A(0),X(0),id(0)    {}    explicit MyData(int):A(97),X(CV_PI),id("mydata1234")    {}    void write(FileStorage& fs) const  // 向文件写入函数，将MyData的数据以map的形式写入文件    {                                   //"{"表示map,"["表示sequence.        fs<<"{"<<"A"<<A<<"X"<<X<<"id"<<id<<"}";    }    void read(const FileNode& node)    // 读文件函数，将文件中特定的数据读入MyData的数据成员中    {        A = (int)node["A"];        X = (double)node["X"];        id = (string)node["id"];    }public：    int A;    double X;    string id;}; // end MyDatastatic void write(FileStorage& fs,const std::string& ,const MyData& x){    x.write(fs);}static void read(const FileNode& node,MyData& x,const MyData& default_value = MyData()){    if(node.empty())        x = default_value;    else        x.read(node);}static ostream& operator<<(ostream& out,const MyData& m){    out<<"{ id = "<<m.id<<",";    out<<"X = "<<m.X<<",";    out<<"A = "<<m.A<<"}";    return out;}int main(int ac,char** av){    if(ac != 2)    {        help(av);        return 1;    }    string filename = av[1];    {        // write        Mat R = Mat_<uchar>::eye(3,3);            T = Mat_<double>::zeros(3,1);        MyData m(1);        FileStorage fs(filename,FileStorage::WRITE);  // 将fs对象和文件关联起来，即打开一个文件。        fs<<"iterationNr"<<100;        fs<<"strings"<<"[";                    // 写一个字符序列，注意"["表示sequence        fs<<"image1.jpg"<<"Awesomeness"<<"../data/bacoon.jpg";        fs<<"]";                               // 字符写完毕        fs<<"Mapping";        fs<<"R"<<R;        fs<<"T"<<T;        fs<<"MyData"<<m;        fs.reslease();                        // 关闭fs打开的文件        cout<<"Write done."<<endl;    }    {// 读操作        cout<<endl<<"Reading: "<<endl;        FileStorage fs;        fs.open(filename,FileStorage::READ);        int itNr;        // fs["iterationNr"]>>itNr;        itNr = (int)fs["iterationNr"]; // 读取文件中的某一项并赋值给itNr,注意此处强制类型转换，和上面功能相同        cout<<itNr;        if(!fs.isOpened())        {            cerr<<"Failed to open "<<filename<<endl;            help(av);            return 1;        }        FileNode n = fs["strings"];    // 读取string 序列        if(n.type() != FileNode::SEQ)  // 检查n是否是序列对象        {            cerr<<"strings is not a sequence! FAIL"<<endl;            return 1;        }        FileNodeIterator it = n.begin(),it_end = n.end(); // 和STL风格类似的迭代器        for(; it != it_end;it++)        {            cout<<(string)*it<<endl;        }        n = fs["Mapping"];              // 读取map结构        cout<<"Two "<<(int)(n["Two"])<<";";        cout<<"One "<<(int)(n["One"])<<endl<<endl;        MyData m;        Mat R,T;        fs["R"]>>R;        fs["T"]>>T;        fs["MyData"]>>m;        cout<<endl            <<"R = "<<R<<endl;        cout<<"T = "<<T<<endl;        cout<<"MyData = "<<m<<endl<<endl;        // 展示对不存在的节点的读取特性        cout<<"Attempt to reand NonExisting(should initialize the data structure with its default)."        fs["NonExisting"]>>m;        cout<<endl<<"NonExisting"<<m<<endl;    }    cout<<endl        <<"Tip: Open up "<<filename<<" with a text editor to see the serialized data."    return 0;}