1. XML、YAML文件的打開和關(guān)閉
XML\YAML文件在OpenCV中的數(shù)據(jù)結(jié)構(gòu)為FileStorage,,打開操作例如:
- string filename = "I.xml";
- FileStorage fs(filename, FileStorage::WRITE);
- \\...
- fs.open(filename, FileStorage::READ);
文件關(guān)閉操作會在FileStorage結(jié)構(gòu)銷毀時(shí)自動(dòng)進(jìn)行,,但也可調(diào)用如下函數(shù)實(shí)現(xiàn)
2.文本和數(shù)字的輸入和輸出
寫入文件使用 << 運(yùn)算符,例如:
- fs << "iterationNr" << 100;
讀取文件,,使用 >> 運(yùn)算符,,例如
- int itNr;
- fs["iterationNr"] >> itNr;
- itNr = (int) fs["iterationNr"];
3. OpenCV數(shù)據(jù)結(jié)構(gòu)的輸入和輸出,和基本的C++形式相同
- Mat R = Mat_<uchar >::eye (3, 3),
- T = Mat_<double>::zeros(3, 1);
- fs << "R" << R; // Write cv::Mat
- fs << "T" << T;
- fs["R"] >> R; // Read cv::Mat
- fs["T"] >> T;
4. vector(arrays) 和 maps的輸入和輸出
vector要注意在第一個(gè)元素前加上“[”,,在最后一個(gè)元素前加上"]",。例如:
- fs << "strings" << "["; // text - string sequence
- fs << "image1.jpg" << "Awesomeness" << "baboon.jpg";
- fs << "]"; // close sequence
對于map結(jié)構(gòu)的操作使用的符號是"{"和"}",例如:
- fs << "Mapping"; // text - mapping
- fs << "{" << "One" << 1;
- fs << "Two" << 2 << "}";
讀取這些結(jié)構(gòu)的時(shí)候,,會用到FileNode和FileNodeIterator數(shù)據(jù)結(jié)構(gòu),。對FileStorage類的[]操作符會返回FileNode數(shù)據(jù)類型,對于一連串的node,,可以使用FileNodeIterator結(jié)構(gòu),,例如:
- 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;
5. 讀寫自己的數(shù)據(jù)結(jié)構(gòu)
這部分比較復(fù)雜,參考最后的實(shí)例中的MyData結(jié)構(gòu)自己領(lǐng)悟吧
最后,,我這里上一個(gè)實(shí)例,,供大家參考,。
源文件里填入如下代碼:
- #include <opencv2/core/core.hpp>
- #include <iostream>
- #include <string>
-
- using namespace cv;
- using namespace std;
-
- 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
- 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);
- }
-
- // This function will print our custom class to the console
- 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);
-
- fs << "iterationNr" << 100;
- fs << "strings" << "["; // text - string sequence
- fs << "image1.jpg" << "Awesomeness" << "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;
- }
編譯后,在命令行進(jìn)入到文件目錄,,執(zhí)行test test.xml,,運(yùn)行結(jié)果如下,生成一個(gè)test . xml文件,,內(nèi)容如下:
- <?xml version="1.0" ?>
- - <opencv_storage>
- <iterationNr>100</iterationNr>
- <strings>image1.jpg Awesomeness baboon.jpg</strings>
- - <Mapping>
- <One>1</One>
- <Two>2</Two>
- </Mapping>
- - <R type_id="opencv-matrix">
- <rows>3</rows>
- <cols>3</cols>
- <dt>u</dt>
- <data>1 0 0 0 1 0 0 0 1</data>
- </R>
- - <T type_id="opencv-matrix">
- <rows>3</rows>
- <cols>1</cols>
- <dt>d</dt>
- <data>0. 0. 0.</data>
- </T>
- - <MyData>
- <A>97</A>
- <X>3.1415926535897931e+000</X>
- <id>mydata1234</id>
- </MyData>
- </opencv_storage>
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