OpenCV  4.1.0
Open Source Computer Vision
Public Types | Public Member Functions | Static Public Member Functions | Public Attributes | Related Functions | List of all members
cv::FileStorage Class Reference
XML/YAML Persistence

XML/YAML/JSON file storage class that encapsulates all the information necessary for writing or reading data to/from a file. More...

#include <opencv2/core/persistence.hpp>

Public Types

enum  Mode {
  READ = 0,
  WRITE = 1,
  APPEND = 2,
  MEMORY = 4,
  FORMAT_MASK = (7<<3),
  FORMAT_AUTO = 0,
  FORMAT_XML = (1<<3),
  FORMAT_YAML = (2<<3),
  FORMAT_JSON = (3<<3),
  BASE64 = 64,
  WRITE_BASE64 = BASE64 | WRITE
}
 file storage mode More...
 
enum  State {
  UNDEFINED = 0,
  VALUE_EXPECTED = 1,
  NAME_EXPECTED = 2,
  INSIDE_MAP = 4
}
 

Public Member Functions

 FileStorage ()
 The constructors.
 
 FileStorage (const String &filename, int flags, const String &encoding=String())
 Opens a file.
 
virtual ~FileStorage ()
 the destructor. calls release()
 
void endWriteStruct ()
 
FileNode getFirstTopLevelNode () const
 Returns the first element of the top-level mapping.
 
int getFormat () const
 Returns the current format.
 
virtual bool isOpened () const
 Checks whether the file is opened.
 
virtual bool open (const String &filename, int flags, const String &encoding=String())
 Opens a file.
 
FileNode operator[] (const String &nodename) const
 Returns the specified element of the top-level mapping.
 
FileNode operator[] (const char *nodename) const
 
virtual void release ()
 Closes the file and releases all the memory buffers.
 
virtual String releaseAndGetString ()
 Closes the file and releases all the memory buffers.
 
FileNode root (int streamidx=0) const
 Returns the top-level mapping.
 
void startWriteStruct (const String &name, int flags, const String &typeName)
 
void write (const String &name, int val)
 Simplified writing API to use with bindings.
 
void write (const String &name, double val)
 
void write (const String &name, const String &val)
 
void write (const String &name, const Mat &val)
 
void write (const String &name, const std::vector< String > &val)
 
void writeComment (const String &comment, bool append=false)
 Writes a comment.
 
void writeRaw (const String &fmt, const void *vec, size_t len)
 Writes multiple numbers.
 

Static Public Member Functions

static String getDefaultObjectName (const String &filename)
 Returns the normalized object name for the specified name of a file.
 

Public Attributes

std::string elname
 
Ptr< Impl > p
 
int state
 

Related Functions

(Note that these are not member functions.)

FileStorage & operator<< (FileStorage &fs, const String &str)
 Writes string to a file storage.
 
void write (FileStorage &fs, const String &name, int value)
 
void write (FileStorage &fs, const String &name, float value)
 
void write (FileStorage &fs, const String &name, double value)
 
void write (FileStorage &fs, const String &name, const String &value)
 
void write (FileStorage &fs, const String &name, const Mat &value)
 
void write (FileStorage &fs, const String &name, const SparseMat &value)
 
void writeScalar (FileStorage &fs, int value)
 
void writeScalar (FileStorage &fs, float value)
 
void writeScalar (FileStorage &fs, double value)
 
void writeScalar (FileStorage &fs, const String &value)
 
template<typename _Tp >
static void write (FileStorage &fs, const _Tp &value)
 
template<>
void write (FileStorage &fs, const int &value)
 
template<>
void write (FileStorage &fs, const float &value)
 
template<>
void write (FileStorage &fs, const double &value)
 
template<>
void write (FileStorage &fs, const String &value)
 
template<typename _Tp >
static void write (FileStorage &fs, const Point_< _Tp > &pt)
 
template<typename _Tp >
static void write (FileStorage &fs, const Point3_< _Tp > &pt)
 
template<typename _Tp >
static void write (FileStorage &fs, const Size_< _Tp > &sz)
 
template<typename _Tp >
static void write (FileStorage &fs, const Complex< _Tp > &c)
 
template<typename _Tp >
static void write (FileStorage &fs, const Rect_< _Tp > &r)
 
template<typename _Tp , int cn>
static void write (FileStorage &fs, const Vec< _Tp, cn > &v)
 
template<typename _Tp , int m, int n>
static void write (FileStorage &fs, const Matx< _Tp, m, n > &x)
 
template<typename _Tp >
static void write (FileStorage &fs, const Scalar_< _Tp > &s)
 
static void write (FileStorage &fs, const Range &r)
 
template<typename _Tp >
static void write (FileStorage &fs, const std::vector< _Tp > &vec)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const Point_< _Tp > &pt)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const Point3_< _Tp > &pt)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const Size_< _Tp > &sz)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const Complex< _Tp > &c)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const Rect_< _Tp > &r)
 
template<typename _Tp , int cn>
static void write (FileStorage &fs, const String &name, const Vec< _Tp, cn > &v)
 
template<typename _Tp , int m, int n>
static void write (FileStorage &fs, const String &name, const Matx< _Tp, m, n > &x)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const Scalar_< _Tp > &s)
 
static void write (FileStorage &fs, const String &name, const Range &r)
 
static void write (FileStorage &fs, const String &name, const KeyPoint &kpt)
 
static void write (FileStorage &fs, const String &name, const DMatch &m)
 
template<typename _Tp , typename std::enable_if< std::is_enum< _Tp >::value >::type * = nullptr>
static void write (FileStorage &fs, const String &name, const _Tp &val)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const std::vector< _Tp > &vec)
 
template<typename _Tp >
static void write (FileStorage &fs, const String &name, const std::vector< std::vector< _Tp > > &vec)
 
template<typename _Tp >
static FileStorage & operator<< (FileStorage &fs, const _Tp &value)
 Writes data to a file storage.
 
static FileStorage & operator<< (FileStorage &fs, const char *str)
 Writes data to a file storage.
 
static FileStorage & operator<< (FileStorage &fs, char *value)
 Writes data to a file storage.
 

Detailed Description

XML/YAML/JSON file storage class that encapsulates all the information necessary for writing or reading data to/from a file.

Examples:
samples/cpp/filestorage.cpp, samples/cpp/tutorial_code/features2D/Homography/decompose_homography.cpp, samples/cpp/tutorial_code/features2D/Homography/homography_from_camera_displacement.cpp, and samples/cpp/tutorial_code/features2D/Homography/pose_from_homography.cpp.

Member Enumeration Documentation

enum cv::FileStorage::Mode

file storage mode

Enumerator
READ 

value, open the file for reading

WRITE 

value, open the file for writing

APPEND 

value, open the file for appending

MEMORY 

returned by FileStorage::release)

flag, read data from source or write data to the internal buffer (which is

FORMAT_MASK 

mask for format flags

FORMAT_AUTO 

flag, auto format

FORMAT_XML 

flag, XML format

FORMAT_YAML 

flag, YAML format

FORMAT_JSON 

flag, JSON format

BASE64 

flag, write rawdata in Base64 by default. (consider using WRITE_BASE64)

WRITE_BASE64 

flag, enable both WRITE and BASE64

enum cv::FileStorage::State
Enumerator
UNDEFINED 
VALUE_EXPECTED 
NAME_EXPECTED 
INSIDE_MAP 

Constructor & Destructor Documentation

cv::FileStorage::FileStorage ( )
Python:
<FileStorage object>=cv.FileStorage()
<FileStorage object>=cv.FileStorage(filename, flags[, encoding])

The constructors.

The full constructor opens the file. Alternatively you can use the default constructor and then call FileStorage::open.

cv::FileStorage::FileStorage ( const String &  filename,
int  flags,
const String &  encoding = String() 
)
Python:
<FileStorage object>=cv.FileStorage()
<FileStorage object>=cv.FileStorage(filename, flags[, encoding])

Opens a file.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.See description of parameters in FileStorage::FileStorage. The method calls FileStorage::release before opening the file.

Parameters
filenameName of the file to open or the text string to read the data from. Extension of the file (.xml, .yml/.yaml or .json) determines its format (XML, YAML or JSON respectively). Also you can append .gz to work with compressed files, for example myHugeMatrix.xml.gz. If both FileStorage::WRITE and FileStorage::MEMORY flags are specified, source is used just to specify the output file format (e.g. mydata.xml, .yml etc.). A file name can also contain parameters. You can use this format, "*?base64" (e.g. "file.json?base64" (case sensitive)), as an alternative to FileStorage::BASE64 flag.
flagsMode of operation. One of FileStorage::Mode
encodingEncoding of the file. Note that UTF-16 XML encoding is not supported currently and you should use 8-bit encoding instead of it.
virtual cv::FileStorage::~FileStorage ( )
virtual

the destructor. calls release()

Member Function Documentation

void cv::FileStorage::endWriteStruct ( )
static String cv::FileStorage::getDefaultObjectName ( const String &  filename)
static

Returns the normalized object name for the specified name of a file.

Parameters
filenameName of a file
Returns
The normalized object name.
FileNode cv::FileStorage::getFirstTopLevelNode ( ) const
Python:
retval=cv.FileStorage.getFirstTopLevelNode()

Returns the first element of the top-level mapping.

Returns
The first element of the top-level mapping.
int cv::FileStorage::getFormat ( ) const
Python:
retval=cv.FileStorage.getFormat()

Returns the current format.

Returns
The current format, see FileStorage::Mode
virtual bool cv::FileStorage::isOpened ( ) const
virtual
Python:
retval=cv.FileStorage.isOpened()

Checks whether the file is opened.

Returns
true if the object is associated with the current file and false otherwise. It is a good practice to call this method after you tried to open a file.
Examples:
samples/cpp/filestorage.cpp.
virtual bool cv::FileStorage::open ( const String &  filename,
int  flags,
const String &  encoding = String() 
)
virtual
Python:
retval=cv.FileStorage.open(filename, flags[, encoding])

Opens a file.

See description of parameters in FileStorage::FileStorage. The method calls FileStorage::release before opening the file.

Parameters
filenameName of the file to open or the text string to read the data from. Extension of the file (.xml, .yml/.yaml or .json) determines its format (XML, YAML or JSON respectively). Also you can append .gz to work with compressed files, for example myHugeMatrix.xml.gz. If both FileStorage::WRITE and FileStorage::MEMORY flags are specified, source is used just to specify the output file format (e.g. mydata.xml, .yml etc.). A file name can also contain parameters. You can use this format, "*?base64" (e.g. "file.json?base64" (case sensitive)), as an alternative to FileStorage::BASE64 flag.
flagsMode of operation. One of FileStorage::Mode
encodingEncoding of the file. Note that UTF-16 XML encoding is not supported currently and you should use 8-bit encoding instead of it.
FileNode cv::FileStorage::operator[] ( const String &  nodename) const
Python:
retval=cv.FileStorage.getNode(nodename)

Returns the specified element of the top-level mapping.

Parameters
nodenameName of the file node.
Returns
Node with the given name.
FileNode cv::FileStorage::operator[] ( const char *  nodename) const
Python:
retval=cv.FileStorage.getNode(nodename)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

virtual void cv::FileStorage::release ( )
virtual
Python:
None=cv.FileStorage.release()

Closes the file and releases all the memory buffers.

Call this method after all I/O operations with the storage are finished.

virtual String cv::FileStorage::releaseAndGetString ( )
virtual
Python:
retval=cv.FileStorage.releaseAndGetString()

Closes the file and releases all the memory buffers.

Call this method after all I/O operations with the storage are finished. If the storage was opened for writing data and FileStorage::WRITE was specified

Examples:
samples/cpp/filestorage.cpp.
FileNode cv::FileStorage::root ( int  streamidx = 0) const
Python:
retval=cv.FileStorage.root([, streamidx])

Returns the top-level mapping.

Parameters
streamidxZero-based index of the stream. In most cases there is only one stream in the file. However, YAML supports multiple streams and so there can be several.
Returns
The top-level mapping.
void cv::FileStorage::startWriteStruct ( const String &  name,
int  flags,
const String &  typeName 
)
void cv::FileStorage::write ( const String &  name,
int  val 
)
Python:
None=cv.FileStorage.write(name, val)

Simplified writing API to use with bindings.

Parameters
nameName of the written object
valValue of the written object
void cv::FileStorage::write ( const String &  name,
double  val 
)
Python:
None=cv.FileStorage.write(name, val)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

void cv::FileStorage::write ( const String &  name,
const String &  val 
)
Python:
None=cv.FileStorage.write(name, val)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

void cv::FileStorage::write ( const String &  name,
const Mat &  val 
)
Python:
None=cv.FileStorage.write(name, val)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

void cv::FileStorage::write ( const String &  name,
const std::vector< String > &  val 
)
Python:
None=cv.FileStorage.write(name, val)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

void cv::FileStorage::writeComment ( const String &  comment,
bool  append = false 
)
Python:
None=cv.FileStorage.writeComment(comment[, append])

Writes a comment.

The function writes a comment into file storage. The comments are skipped when the storage is read.

Parameters
commentThe written comment, single-line or multi-line
appendIf true, the function tries to put the comment at the end of current line. Else if the comment is multi-line, or if it does not fit at the end of the current line, the comment starts a new line.
void cv::FileStorage::writeRaw ( const String &  fmt,
const void *  vec,
size_t  len 
)

Writes multiple numbers.

Writes one or more numbers of the specified format to the currently written structure. Usually it is more convenient to use operator << instead of this method.

Parameters
fmtSpecification of each array element, see format specification
vecPointer to the written array.
lenNumber of the uchar elements to write.

Friends And Related Function Documentation

FileStorage & operator<< ( FileStorage &  fs,
const String &  str 
)
related

Writes string to a file storage.

template<typename _Tp >
static FileStorage & operator<< ( FileStorage &  fs,
const _Tp &  value 
)
related

Writes data to a file storage.

static FileStorage & operator<< ( FileStorage &  fs,
const char *  str 
)
related

Writes data to a file storage.

static FileStorage & operator<< ( FileStorage &  fs,
char *  value 
)
related

Writes data to a file storage.

void write ( FileStorage &  fs,
const String &  name,
int  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const String &  name,
float  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const String &  name,
double  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const String &  name,
const String &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const String &  name,
const Mat &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const String &  name,
const SparseMat &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const _Tp &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const int &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const float &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const double &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
void write ( FileStorage &  fs,
const String &  value 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const Point_< _Tp > &  pt 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const Point3_< _Tp > &  pt 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const Size_< _Tp > &  sz 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const Complex< _Tp > &  c 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const Rect_< _Tp > &  r 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp , int cn>
static void write ( FileStorage &  fs,
const Vec< _Tp, cn > &  v 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp , int m, int n>
static void write ( FileStorage &  fs,
const Matx< _Tp, m, n > &  x 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const Scalar_< _Tp > &  s 
)
related
Python:
None=cv.FileStorage.write(name, val)
static void write ( FileStorage &  fs,
const Range &  r 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const std::vector< _Tp > &  vec 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const Point_< _Tp > &  pt 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const Point3_< _Tp > &  pt 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const Size_< _Tp > &  sz 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const Complex< _Tp > &  c 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const Rect_< _Tp > &  r 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp , int cn>
static void write ( FileStorage &  fs,
const String &  name,
const Vec< _Tp, cn > &  v 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp , int m, int n>
static void write ( FileStorage &  fs,
const String &  name,
const Matx< _Tp, m, n > &  x 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const Scalar_< _Tp > &  s 
)
related
Python:
None=cv.FileStorage.write(name, val)
static void write ( FileStorage &  fs,
const String &  name,
const Range &  r 
)
related
Python:
None=cv.FileStorage.write(name, val)
static void write ( FileStorage &  fs,
const String &  name,
const KeyPoint &  kpt 
)
related
Python:
None=cv.FileStorage.write(name, val)
static void write ( FileStorage &  fs,
const String &  name,
const DMatch &  m 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp , typename std::enable_if< std::is_enum< _Tp >::value >::type * = nullptr>
static void write ( FileStorage &  fs,
const String &  name,
const _Tp &  val 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const std::vector< _Tp > &  vec 
)
related
Python:
None=cv.FileStorage.write(name, val)
template<typename _Tp >
static void write ( FileStorage &  fs,
const String &  name,
const std::vector< std::vector< _Tp > > &  vec 
)
related
Python:
None=cv.FileStorage.write(name, val)
void writeScalar ( FileStorage &  fs,
int  value 
)
related
void writeScalar ( FileStorage &  fs,
float  value 
)
related
void writeScalar ( FileStorage &  fs,
double  value 
)
related
void writeScalar ( FileStorage &  fs,
const String &  value 
)
related

Member Data Documentation

std::string cv::FileStorage::elname
Ptr<Impl> cv::FileStorage::p
int cv::FileStorage::state
The documentation for this class was generated from the following file:
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