samples/cpp/filestorage.cpp

使用 FileStorage 接口的完整示例

/*
* filestorage_sample 演示了 OpenCV 序列化功能的使用
 */
 
#include "opencv2/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 演示了 OpenCV 序列化功能的使用。\n"
<< "用法：\n"
<< av[0] << " outputfile.yml.gz\n"
<< "\n上面的 outputfile 可以有许多不同的扩展名，见下文。"
<< "\n该程序演示了 FileStorage 用于序列化的用法，即在 OpenCV 中使用的 << 和 >> \n"
<< "例如，如何创建类并使其序列化，以及如何使用它来读写矩阵。\n"
<< "FileStorage 允许您将数据序列化为各种格式，这些格式由文件扩展名指定。"
<< "\n您应该尝试使用不同的文件扩展名（例如 yaml yml xml xml.gz yaml.gz 等...）。\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 // 为此类编写序列化
  {
fs << "{" << "A" << A << "X" << X << "id" << id << "}";
  }
  void read(const FileNode& node) // 读取为此类编写的序列化
  {
 
A = (int)node["A"];
X = (double)node["X"];
    id = (string)node["id"];
  }
};
 
// 这些 write 和 read 函数必须存在，如 operations.hpp 中的内联函数
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)
{
  cv::CommandLineParser parser(ac, av,
    "{@input||}{help h ||}"
  );
  if (parser.has("help"))
  {
help(av);
    return 0;
  }
  string filename = parser.get<string>("@input");
  if (filename.empty())
  {
help(av);
    return 1;
  }
 
  // 写入
  {
    FileStorage fs(filename, FileStorage::WRITE);
 
cout << "写入图像\n";
fs << "images" << "[";
 
fs << "image1.jpg" << "myfi.png" << "baboon.jpg";
cout << "image1.jpg" << " myfi.png" << " baboon.jpg" << endl;
 
fs << "]";
 
cout << "写入矩阵\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 << "写入 MyData 结构体\n";
MyData m(1);
fs << "mdata" << m;
cout << m << endl;
  }
 
  // 读取
  {
    FileStorage fs(filename, FileStorage::READ);
 
    if (!fs.isOpened())
    {
cerr << "无法打开 " << filename << endl;
help(av);
      return 1;
    }
 
    FileNode n = fs["images"];
    if (n.type() != FileNode::SEQ)
    {
cerr << "images 不是序列！失败" << endl;
      return 1;
    }
 
cout << "读取图像\n";
    FileNodeIterator it = n.begin(), it_end = n.end();
    for (; it != it_end; ++it)
    {
cout << (string)*it << "\n";
    }
 
    Mat R, T;
cout << "读取 R 和 T" << endl;
 
fs["R"] >> R;
fs["T"] >> T;
 
cout << "R = " << R << "\n";
cout << "T = " << T << endl;
 
MyData m;
fs["mdata"] >> m;
 
cout << "读取 mdata\n";
cout << m << endl;
 
cout << "尝试读取 mdata_b\n"; // 显示空矩阵的默认行为
fs["mdata_b"] >> m;
cout << "读取 mdata_b\n";
cout << m << endl;
 
  }
 
cout << "尝试打开 " << filename << " 以查看序列化数据。" << endl << endl;
 
  // 从字符串读取
  {
cout << "从字符串读取数据\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 << "尝试从字符串读取 mdata_b\n"; // 显示空矩阵的默认行为
fs["mdata"] >> m;
cout << "读取 mdata\n";
cout << m << endl;
  }
 
  // 写入字符串
  {
cout << "将数据写入字符串\n";
    FileStorage fs(filename, FileStorage::WRITE | FileStorage::MEMORY | FileStorage::FORMAT_YAML);
 
cout << "写入 MyData 结构体\n";
MyData m(1);
fs << "mdata" << m;
cout << m << endl;
    string createdString = fs.releaseAndGetString();
cout << "生成的字符串：\n" << createdString << "\n";
  }
 
  return 0;
}