国内最全IT社区平台 联系我们 | 收藏本站
阿里云优惠2流量王
您当前位置:首页 > php开源 > php教程 > OpenCV3.0 Examples学习笔记(8)-filestorage.cpp

OpenCV3.0 Examples学习笔记(8)-filestorage.cpp

来源:程序员人生   发布时间:2017-03-09 08:35:43 阅读次数:1672次
这个系列的目的是通过对OpenCV示例,进1步了解OpenCV函数的使用,不触及具体原理。

目录
简介
Example运行截图
Example分析
Example代码

简介
本文记录了对OpenCV示例filestorage.cpp的分析。
资料地址:http://docs.opencv.org/3.0.0/d6/d03/filestorage_8cpp-example.html

这个示例主要讲述了如何使用FileStorage类读写yml文件。

FileStorage类提供了对xml,yml文件的读写操作。
FileStorage 具体定义可以参见cv::FileStorage Class Reference



Example截图

生成YML文件内容
%YAML:1.0
images:
   - "image1.jpg"
   - "myfi.png"
   - "../data/baboon.jpg"
R: !!opencv-matrix
   rows: 3
   cols: 3
   dt: d
   data: [ 1., 0., 0., 0., 1., 0., 0., 0., 1. ]
T: !!opencv-matrix
   rows: 3
   cols: 1
   dt: d
   data: [ 0., 0., 0. ]
mdata:
   A: 97
   X: 3.1415926535897931e+000
   id: mydata1234


Example分析
1.使用FileStorage 写文件
1.1.打开1个文件并准备进行写操作
FileStorage fs(filename, FileStorage::WRITE);

注意:
(1)FileStorage处理支持xml,yml外, 还支持gz的紧缩格式。


1.2.创建images结点,并写入"image1.jpg", "myfi.png" ,"../data/baboon.jpg"3个字段
fs << "images" << "[";

    fs << "image1.jpg" << "myfi.png" << "../data/baboon.jpg";
    cout << "image1.jpg" << " myfi.png" << " ../data/baboon.jpg" << endl;

    fs << "]";

1.3.在文件中嵌入Mat数据,并分别生成节点R,T
cout << "writing mats\n";
    Mat R =Mat_<double>::eye(3, 3),T = Mat_<double>::zeros(3, 1);
    cout << "R = " << R << "\n";
    cout << "T = " << T << "\n";
    fs << "R" << R;
    fs << "T" << T;

1.4.在文件中嵌入自定义数据,并生成mdata节点
cout << "writing MyData struct\n";
    MyData m(1);
    fs << "mdata" << m;
    cout << m << endl;

注意:
根据MyData 结构体定义,其初始化时调用构造函数赋初值。

2.使用FileStorage 读取文件
2.1.打开1个文件并准备进行读操作
FileStorage fs(filename, FileStorage::READ);

    if (!fs.isOpened())
    {
      cerr << "failed to open " << filename << endl;
      help(av);
      return 1;
    }

2.2.读取文件中images节点
    FileNode n = fs["images"];
    if (n.type() != FileNode::SEQ)
    {
      cerr << "images is not a sequence! FAIL" << endl;
      return 1;
    }

2.3.遍历images节点中字符串
    cout << "reading images\n";
    FileNodeIterator it = n.begin(), it_end = n.end();
    for (; it != it_end; ++it)
    {
      cout << (string)*it << "\n";
    }

2.4.读取R,T节点(依照Mat)
    Mat R, T;
    cout << "reading R and T" << endl;

    fs["R"] >> R;
    fs["T"] >> T;

    cout << "R = " << R << "\n";
    cout << "T = " << T << endl;

2.5.读取mdata节点(依照自定义结构体MyData 
    MyData m;
    fs["mdata"] >> m;

    cout << "read mdata\n";
    cout << m << endl;

2.6.尝试读取不存在的节点,验证鲁棒性
    cout << "attempting to read mdata_b\n";   //Show default behavior for empty matrix
    fs["mdata_b"] >> m;
    cout << "read mdata_b\n";
    cout << m << endl;

3.从string中读
3.1创建string 
cout << "Read data from string\n";
    string dataString =
        "%YAML:1.0\n"
        "mdata:\n"
        "   A: 97\n"
        "   X: 3.1415926535897931e+00\n"
        "   id: mydata1234\n";

3.2创建自定义结构体MyData 对象
MyData m;

3.3创建对内存读取的FileStorage 对象
    FileStorage fs(dataString, FileStorage::READ | FileStorage::MEMORY);

注意:
 (1)FileStorage::MEMORY,表示从source读数据,或向内部缓存写入数据(由FileStorage::release返回)

3.4将dataString内容写入,MyData 对象m中
    cout << "attempting to read mdata_b from string\n";   //Show default behavior for empty matrix
    fs["mdata"] >> m;
    cout << "read mdata\n";
    cout << m << endl;

4.向string中写数据
4.1打开1个文件并进行写操作
cout << "Write data to string\n";
FileStorage fs(filename, FileStorage::WRITE | FileStorage::MEMORY | FileStorage::FORMAT_YAML);

注意:
 (1)由于包括FileStorage::MEMORY,所以其实其实不会写入文件,只是在内存中操作。


4.2创建自定义结构体MyData 对象m
cout << "writing MyData struct\n";
MyData m(1);

4.3将数据m写入mdata节点
fs << "mdata" << m;
    cout << m << endl;

4.4关闭对象,并获得其内容
string createdString = fs.releaseAndGetString();
    cout << "Created string:\n" << createdString << "\n";

Example源码

/*
 * filestorage_sample demonstrate the usage of the opencv serialization functionality
 */

#include "opencv2/core/core.hpp"
#include <iostream>
#include <string>

using std::string;
using std::cout;
using std::endl;
using std::cerr;
using std::ostream;
using namespace cv;

static void help(char** av)
{
  cout << "\nfilestorage_sample demonstrate the usage of the opencv serialization functionality.\n"
      << "usage:\n"
      <<  av[0] << " outputfile.yml.gz\n"
      << "\n   outputfile above can have many different extenstions, see below."
      << "\nThis program demonstrates the use of FileStorage for serialization, that is use << and >>  in OpenCV\n"
      << "For example, how to create a class and have it serialize, but also how to use it to read and write matrices.\n"
      << "FileStorage allows you to serialize to various formats specified by the file end type."
          << "\nYou should try using different file extensions.(e.g. yaml yml xml xml.gz yaml.gz etc...)\n" << endl;
}

struct MyData
{
  MyData() :
    A(0), X(0), id()
  {
  }
  explicit MyData(int) :
    A(97), X(CV_PI), id("mydata1234")
  {
  }
  int A;
  double X;
  string id;
  void write(FileStorage& fs) const //Write serialization for this class
  {
    fs << "{" << "A" << A << "X" << X << "id" << id << "}";
  }
  void read(const FileNode& node)  //Read serialization for this class
  {

    A = (int)node["A"];
    X = (double)node["X"];
    id = (string)node["id"];
  }
};

//These write and read functions must exist as per the inline functions in operations.hpp
static 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
  {
    FileStorage fs(filename, FileStorage::WRITE);

    cout << "writing images\n";
    fs << "images" << "[";

    fs << "image1.jpg" << "myfi.png" << "../data/baboon.jpg";
    cout << "image1.jpg" << " myfi.png" << " ../data/baboon.jpg" << endl;

    fs << "]";

    cout << "writing mats\n";
    Mat R =Mat_<double>::eye(3, 3),T = Mat_<double>::zeros(3, 1);
    cout << "R = " << R << "\n";
    cout << "T = " << T << "\n";
    fs << "R" << R;
    fs << "T" << T;

    cout << "writing MyData struct\n";
    MyData m(1);
    fs << "mdata" << m;
    cout << m << endl;
  }

  //read
  {
    FileStorage fs(filename, FileStorage::READ);

    if (!fs.isOpened())
    {
      cerr << "failed to open " << filename << endl;
      help(av);
      return 1;
    }

    FileNode n = fs["images"];
    if (n.type() != FileNode::SEQ)
    {
      cerr << "images is not a sequence! FAIL" << endl;
      return 1;
    }

    cout << "reading images\n";
    FileNodeIterator it = n.begin(), it_end = n.end();
    for (; it != it_end; ++it)
    {
      cout << (string)*it << "\n";
    }

    Mat R, T;
    cout << "reading R and T" << endl;

    fs["R"] >> R;
    fs["T"] >> T;

    cout << "R = " << R << "\n";
    cout << "T = " << T << endl;

    MyData m;
    fs["mdata"] >> m;

    cout << "read mdata\n";
    cout << m << endl;

    cout << "attempting to read mdata_b\n";   //Show default behavior for empty matrix
    fs["mdata_b"] >> m;
    cout << "read mdata_b\n";
    cout << m << endl;

  }

  cout << "Try opening " << filename << " to see the serialized data." << endl << endl;

  //read from string
  {
    cout << "Read data from string\n";
    string dataString =
        "%YAML:1.0\n"
        "mdata:\n"
        "   A: 97\n"
        "   X: 3.1415926535897931e+00\n"
        "   id: mydata1234\n";
    MyData m;
    FileStorage fs(dataString, FileStorage::READ | FileStorage::MEMORY);
    cout << "attempting to read mdata_b from string\n";   //Show default behavior for empty matrix
    fs["mdata"] >> m;
    cout << "read mdata\n";
    cout << m << endl;
  }

  //write to string
  {
    cout << "Write data to string\n";
    FileStorage fs(filename, FileStorage::WRITE | FileStorage::MEMORY | FileStorage::FORMAT_YAML);

    cout << "writing MyData struct\n";
    MyData m(1);
    fs << "mdata" << m;
    cout << m << endl;
    string createdString = fs.releaseAndGetString();
    cout << "Created string:\n" << createdString << "\n";
  }

  return 0;
}

参考资料:

1.《OpenCV使用FileStorage保存Mat数据
2.《OpenCV编程->FileStorage解析
3.《OpenCV FileStorage 使用记录
4.《Yml文件的读取与写入
5.《OpenCV —FileStorage类的数据读写操作与示例
6.《OpenCV持久化(1)
生活不易,码农辛苦
如果您觉得本网站对您的学习有所帮助,可以手机扫描二维码进行捐赠
程序员人生
------分隔线----------------------------
分享到:
------分隔线----------------------------
关闭
程序员人生