目标

您会找到以下问题的答案：如何使用YAML或XML文件打印和读取文本和OpenCV文本条目？

OpenCV数据结构如何做同样的操作？

如何为您的数据结构做这个？

源代码

您可以从这里下载，也可以在samples/cpp/tutorial_code/core/file_input_output/file_input_output.cppOpenCV源代码库中找到它。

以下是如何实现目标列表中枚举的所有内容的示例代码。#include

#include

#include

using namespace cv;

using namespace std;

static void help(char** av)

{

cout << endl

<< av[0] << " shows the usage of the OpenCV serialization functionality." << endl

<< "usage: " << endl

<< av[0] << " outputfile.yml.gz" << endl

<< "The output file may be either XML (xml) or YAML (yml/yaml). You can even compress it by "

<< "specifying this in its extension like xml.gz yaml.gz etc... " << endl

<< "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;

}

class MyData

{

public:

MyData() : A(0), X(0), id()

{}

explicit MyData(int) : A(97), X(CV_PI), id("mydata1234") // explicit to avoid implicit conversion

{}

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"];

}

public: // Data Members

int A;

double X;

string id;

};

//These write and read functions must be defined for the serialization in FileStorage to work

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);

}

// This function will print our custom class to the console

static ostream& operator<

{

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_::eye(3, 3),

T = Mat_::zeros(3, 1);

MyData m(1);

FileStorage fs(filename, FileStorage::WRITE);

fs << "iterationNr" << 100;

fs << "strings" << "["; // text - string sequence

fs << "image1.jpg" << "Awesomeness" << "../data/baboon.jpg";

fs << "]"; // close sequence

fs << "Mapping"; // text - mapping

fs << "{" << "One" << 1;

fs << "Two" << 2 << "}";

fs << "R" << R; // cv::Mat

fs << "T" << T;

fs << "MyData" << m; // your own data structures

fs.release(); // explicit close

cout << "Write Done." << endl;

}

{//read

cout << endl << "Reading: " << endl;

FileStorage fs;

fs.open(filename, FileStorage::READ);

int itNr;

//fs["iterationNr"] >> itNr;

itNr = (int) fs["iterationNr"];

cout << itNr;

if (!fs.isOpened())

{

cerr << "Failed to open " << filename << endl;

help(av);

return 1;

}

FileNode n = fs["strings"]; // Read string sequence - Get node

if (n.type() != FileNode::SEQ)

{

cerr << "strings is not a sequence! FAIL" << endl;

return 1;

}

FileNodeIterator it = n.begin(), it_end = n.end(); // Go through the node

for (; it != it_end; ++it)

cout << (string)*it << endl;

n = fs["Mapping"]; // Read mappings from a sequence

cout << "Two " << (int)(n["Two"]) << "; ";

cout << "One " << (int)(n["One"]) << endl << endl;

MyData m;

Mat R, T;

fs["R"] >> R; // Read cv::Mat

fs["T"] >> T;

fs["MyData"] >> m; // Read your own structure_

cout << endl

<< "R = " << R << endl;

cout << "T = " << T << endl << endl;

cout << "MyData = " << endl << m << endl << endl;

//Show default behavior for non existing nodes

cout << "Attempt to read NonExisting (should initialize the data structure with its default).";

fs["NonExisting"] >> m;

cout << endl << "NonExisting = " << endl << m << endl;

}

cout << endl

<< "Tip: Open up " << filename << " with a text editor to see the serialized data." << endl;

return 0;

}

说明

这里我们仅谈论XML和YAML文件输入。您的输出(及其相应的输入)文件可能只有这些扩展中的一个和结构来自此。它们是可以序列化的两种数据结构：映射(如STL映射)和元素序列(如STL向量)。这些之间的区别是，在地图中，每个元素都有一个唯一的名称，通过您可以访问它。对于序列，您需要通过它们查询特定项目。XML / YAML文件打开和关闭。在将任何内容写入此类文件之前，您需要将其打开并结束关闭。OpenCV中的XML / YAML数据结构是cv :: FileStorage。要指定文件在硬盘驱动器上绑定的结构，您可以使用其构造函数或open()函数：string filename = "I.xml";

FileStorage fs(filename, FileStorage::WRITE);

//...

fs.open(filename, FileStorage::READ);

您使用第二个参数中的任何一个是一个常数，指定您可以在其上执行的操作类型：WRITE，READ或APPEND。文件名中指定的扩展名也可以确定要使用的输出格式。如果指定扩展名，例如* .xml.gz *，输出可能会被压缩。

当cv :: FileStorage对象被销毁时，文件会自动关闭。但是，您可以使用发布功能显式地调用此功能：fs.release(); // explicit close文本和数字的输入和输出。数据结构使用与STL库相同的<

读入是一个简单的寻址(通过[]操作符)和转换操作或通过>>操作符读取：int itNr;

fs["iterationNr"] >> itNr;

itNr = (int) fs["iterationNr"];

OpenCV数据结构的输入/输出。那么这些行为就像基本的C ++类型一样：Mat R = Mat_::eye (3, 3),

T = Mat_::zeros(3, 1);

fs << "R" << R; // Write cv::Mat

fs << "T" << T;

fs["R"] >> R; // Read cv::Mat

fs["T"] >> T;

向量(数组)和关联图的输入/输出。如前所述，我们可以输出地图和序列(数组，向量)。再次，我们首先打印变量的名称，然后我们必须指定我们的输出是序列还是地图。对于第一个元素之前的序列打印“[”字符，最后一个“]”字符后：fs << "strings" << "["; // text - string sequence

fs << "image1.jpg" << "Awesomeness" << "baboon.jpg";

fs << "]"; // close sequence

对于地图，钻头是一样的，现在我们使用“{”和“}”分隔符：fs << "Mapping"; // text - mapping

fs << "{" << "One" << 1;

fs << "Two" << 2 << "}";FileNode n = fs["strings"]; // Read string sequence - Get node

if (n.type() != FileNode::SEQ)

{

cerr << "strings is not a sequence! FAIL" << endl;

return 1;

}

FileNodeIterator it = n.begin(), it_end = n.end(); // Go through the node

for (; it != it_end; ++it)

cout << (string)*it << endl;

对于地图，您可以再次使用[]运算符来访问给定项目(或>>运算符)：n = fs["Mapping"]; // Read mappings from a sequence

cout << "Two " << (int)(n["Two"]) << "; ";

cout << "One " << (int)(n["One"]) << endl << endl;

读写自己的数据结构。假设你有一个数据结构，如：class MyData

{

public:

MyData() : A(0), X(0), id() {}

public: // Data Members

int A;

double X;

string id;

};

通过OpenCV I / O XML / YAML接口(就像OpenCV数据结构一样)，可以通过在类中添加一个读取和写入函数来对其进行序列化。对于内部：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"];

}

那么你需要在类之外添加以下函数定义：void write(FileStorage& fs, const std::string&, const MyData& x)

{

x.write(fs);

}

void read(const FileNode& node, MyData& x, const MyData& default_value = MyData())

{

if(node.empty())

x = default_value;

else

x.read(node);

}

在这里您可以看到，在阅读部分中，我们定义了如果用户尝试读取不存在的节点会发生什么。在这种情况下，我们只返回默认的初始化值，但是更详细的解决方案是返回一个对象ID的减号值。

一旦添加了这四个函数，就可以使用>>操作符进行写操作，而<

fs << "MyData" << m; // your own data structures

fs["MyData"] >> m; // Read your own structure_

或尝试阅读一个不存在的阅读：fs["NonExisting"] >> m; // Do not add a fs << "NonExisting" << m command for this to work

cout << endl << "NonExisting = " << endl << m << endl;

结果

主要是我们打印出定义的数字。您可以在控制台的屏幕上看到：Write Done.

Reading:

100image1.jpg

Awesomeness

baboon.jpg

Two 2; One 1

R = [1, 0, 0;

0, 1, 0;

0, 0, 1]

T = [0; 0; 0]

MyData =

{ id = mydata1234, X = 3.14159, A = 97}

Attempt to read NonExisting (should initialize the data structure with its default).

NonExisting =

{ id = , X = 0, A = 0}

Tip: Open up output.xml with a text editor to see the serialized data.

不过，输出xml文件中可能会看到的更有趣：<?xml version="1.0"?>

100

image1.jpg Awesomeness baboon.jpg

1

2

3

3

u

1 0 0 0 1 0 0 0 1

3

1

d

0. 0. 0.

97

3.1415926535897931e+000

mydata1234

或YAML文件：%YAML:1.0

iterationNr: 100

strings:

- "image1.jpg"

- Awesomeness

- "baboon.jpg"

Mapping:

One: 1

Two: 2

R: !!opencv-matrix

rows: 3

cols: 3

dt: u

data: [ 1, 0, 0, 0, 1, 0, 0, 0, 1 ]

T: !!opencv-matrix

rows: 3

cols: 1

dt: d

data: [ 0., 0., 0. ]

MyData:

A: 97

X: 3.1415926535897931e+000

id: mydata1234