OpenCV  2.4.13.2
Open Source Computer Vision
cv::FileStorage Class Reference

#include <core.hpp>

Public Types

enum  {
  READ =0, WRITE =1, APPEND =2, MEMORY =4,
  FORMAT_MASK =(7<<3), FORMAT_AUTO =0, FORMAT_XML =(1<<3), FORMAT_YAML =(2<<3)
}
 file storage mode More...
 
enum  { UNDEFINED =0, VALUE_EXPECTED =1, NAME_EXPECTED =2, INSIDE_MAP =4 }
 

Public Member Functions

 FileStorage ()
 the default constructor More...
 
 FileStorage (const string &source, int flags, const string &encoding=string())
 the full constructor that opens file storage for reading or writing More...
 
 FileStorage (CvFileStorage *fs)
 the constructor that takes pointer to the C FileStorage structure More...
 
virtual ~FileStorage ()
 the destructor. calls release() More...
 
virtual bool open (const string &filename, int flags, const string &encoding=string())
 opens file storage for reading or writing. The previous storage is closed with release() More...
 
virtual bool isOpened () const
 returns true if the object is associated with currently opened file. More...
 
virtual void release ()
 closes the file and releases all the memory buffers More...
 
string releaseAndGetString ()
 closes the file, releases all the memory buffers and returns the text string More...
 
FileNode getFirstTopLevelNode () const
 returns the first element of the top-level mapping More...
 
FileNode root (int streamidx=0) const
 returns the top-level mapping. YAML supports multiple streams More...
 
FileNode operator[] (const string &nodename) const
 returns the specified element of the top-level mapping More...
 
FileNode operator[] (const char *nodename) const
 returns the specified element of the top-level mapping More...
 
CvFileStorageoperator* ()
 returns pointer to the underlying C FileStorage structure More...
 
const CvFileStorageoperator* () const
 returns pointer to the underlying C FileStorage structure More...
 
void writeRaw (const string &fmt, const uchar *vec, size_t len)
 writes one or more numbers of the specified format to the currently written structure More...
 
void writeObj (const string &name, const void *obj)
 writes the registered C structure (CvMat, CvMatND, CvSeq). See cvWrite() More...
 

Static Public Member Functions

static string getDefaultObjectName (const string &filename)
 returns the normalized object name for the specified file name More...
 

Public Attributes

Ptr< CvFileStoragefs
 the underlying C FileStorage structure More...
 
string elname
 the currently written element More...
 
vector< char > structs
 the stack of written structures More...
 
int state
 the writer state More...
 

Detailed Description

XML/YAML File Storage Class.

The class describes an object associated with XML or YAML file. It can be used to store data to such a file or read and decode the data.

The storage is organized as a tree of nested sequences (or lists) and mappings. Sequence is a heterogenious array, which elements are accessed by indices or sequentially using an iterator. Mapping is analogue of std::map or C structure, which elements are accessed by names. The most top level structure is a mapping. Leaves of the file storage tree are integers, floating-point numbers and text strings.

For example, the following code:

// open file storage for writing. Type of the file is determined from the extension
fs << "test_int" << 5 << "test_real" << 3.1 << "test_string" << "ABCDEFGH";
fs << "test_mat" << Mat::eye(3,3,CV_32F);
fs << "test_list" << "[" << 0.0000000000001 << 2 << CV_PI << -3435345 << "2-502 2-029 3egegeg" <<
"{:" << "month" << 12 << "day" << 31 << "year" << 1969 << "}" << "]";
fs << "test_map" << "{" << "x" << 1 << "y" << 2 << "width" << 100 << "height" << 200 << "lbp" << "[:";
const uchar arr[] = {0, 1, 1, 0, 1, 1, 0, 1};
fs.writeRaw("u", arr, (int)(sizeof(arr)/sizeof(arr[0])));
fs << "]" << "}";

will produce the following file:

%YAML:1.0
test_int: 5
test_real: 3.1000000000000001e+00
test_string: ABCDEFGH
test_mat: !!opencv-matrix
    rows: 3
    cols: 3
    dt: f
    data: [ 1., 0., 0., 0., 1., 0., 0., 0., 1. ]
test_list:
    - 1.0000000000000000e-13
    - 2
    - 3.1415926535897931e+00
    - -3435345
    - "2-502 2-029 3egegeg"
    - { month:12, day:31, year:1969 }
test_map:
    x: 1
    y: 2
    width: 100
    height: 200
    lbp: [ 0, 1, 1, 0, 1, 1, 0, 1 ]

and to read the file above, the following code can be used:

// open file storage for reading.
// Type of the file is determined from the content, not the extension
int test_int = (int)fs["test_int"];
double test_real = (double)fs["test_real"];
string test_string = (string)fs["test_string"];
Mat M;
fs["test_mat"] >> M;
FileNode tl = fs["test_list"];
CV_Assert(tl.type() == FileNode::SEQ && tl.size() == 6);
double tl0 = (double)tl[0];
int tl1 = (int)tl[1];
double tl2 = (double)tl[2];
int tl3 = (int)tl[3];
string tl4 = (string)tl[4];
CV_Assert(tl[5].type() == FileNode::MAP && tl[5].size() == 3);
int month = (int)tl[5]["month"];
int day = (int)tl[5]["day"];
int year = (int)tl[5]["year"];
FileNode tm = fs["test_map"];
int x = (int)tm["x"];
int y = (int)tm["y"];
int width = (int)tm["width"];
int height = (int)tm["height"];
int lbp_val = 0;
FileNodeIterator it = tm["lbp"].begin();
for(int k = 0; k < 8; k++, ++it)
lbp_val |= ((int)*it) << k;

Member Enumeration Documentation

§ anonymous enum

anonymous enum

file storage mode

Enumerator
READ 
WRITE 

read mode

APPEND 

write mode

MEMORY 

append mode

FORMAT_MASK 
FORMAT_AUTO 
FORMAT_XML 
FORMAT_YAML 

§ anonymous enum

anonymous enum
Enumerator
UNDEFINED 
VALUE_EXPECTED 
NAME_EXPECTED 
INSIDE_MAP 

Constructor & Destructor Documentation

§ FileStorage() [1/3]

cv::FileStorage::FileStorage ( )

the default constructor

§ FileStorage() [2/3]

cv::FileStorage::FileStorage ( const string &  source,
int  flags,
const string &  encoding = string() 
)

the full constructor that opens file storage for reading or writing

§ FileStorage() [3/3]

cv::FileStorage::FileStorage ( CvFileStorage fs)

the constructor that takes pointer to the C FileStorage structure

§ ~FileStorage()

virtual cv::FileStorage::~FileStorage ( )
virtual

the destructor. calls release()

Member Function Documentation

§ getDefaultObjectName()

static string cv::FileStorage::getDefaultObjectName ( const string &  filename)
static

returns the normalized object name for the specified file name

§ getFirstTopLevelNode()

FileNode cv::FileStorage::getFirstTopLevelNode ( ) const
inline

returns the first element of the top-level mapping

§ isOpened()

virtual bool cv::FileStorage::isOpened ( ) const
virtual

returns true if the object is associated with currently opened file.

§ open()

virtual bool cv::FileStorage::open ( const string &  filename,
int  flags,
const string &  encoding = string() 
)
virtual

opens file storage for reading or writing. The previous storage is closed with release()

§ operator*() [1/2]

CvFileStorage* cv::FileStorage::operator* ( )
inline

returns pointer to the underlying C FileStorage structure

§ operator*() [2/2]

const CvFileStorage* cv::FileStorage::operator* ( ) const
inline

returns pointer to the underlying C FileStorage structure

§ operator[]() [1/2]

FileNode cv::FileStorage::operator[] ( const string &  nodename) const

returns the specified element of the top-level mapping

§ operator[]() [2/2]

FileNode cv::FileStorage::operator[] ( const char *  nodename) const

returns the specified element of the top-level mapping

§ release()

virtual void cv::FileStorage::release ( )
virtual

closes the file and releases all the memory buffers

§ releaseAndGetString()

string cv::FileStorage::releaseAndGetString ( )

closes the file, releases all the memory buffers and returns the text string

§ root()

FileNode cv::FileStorage::root ( int  streamidx = 0) const

returns the top-level mapping. YAML supports multiple streams

§ writeObj()

void cv::FileStorage::writeObj ( const string &  name,
const void obj 
)

writes the registered C structure (CvMat, CvMatND, CvSeq). See cvWrite()

§ writeRaw()

void cv::FileStorage::writeRaw ( const string &  fmt,
const uchar vec,
size_t  len 
)

writes one or more numbers of the specified format to the currently written structure

Member Data Documentation

§ elname

string cv::FileStorage::elname

the currently written element

§ fs

Ptr<CvFileStorage> cv::FileStorage::fs

the underlying C FileStorage structure

§ state

int cv::FileStorage::state

the writer state

§ structs

vector<char> cv::FileStorage::structs

the stack of written structures


The documentation for this class was generated from the following files: