CExifEntry Class Reference

EXIF data entry in an image file. More...

#include <ExifEntry.hpp>

Collaboration diagram for CExifEntry:

[legend]List of all members.

Public Member Functions

• CExifEntry (tag_t tag, const TagSpace &tspace)
• CExifEntry (tag_t tag, const TagSpace &tspace, uint16_t type, uint32_t count, uint32_t offset, CTiff *file)
• bool operator< (const CExifEntry &rhs) const
• tag_t Tag () const
• uint32_t Count () const
• const char * LongName () const
• const char * TagName () const
• unsigned char * Data ()
• const unsigned char * Data () const
• uint32_t Size () const
• template<typename T> const T As (std::size_t idx=0) const
• std::string Format () const

Private Member Functions

• bool IsReference () const
• bool IsDataReady () const
• void EnsureDataReady () const

Private Attributes

• CTagDef m_tag

  definition of the tag of this entry
  

• uint16_t m_type

  type of data of this entry.
  

• uint32_t m_count

  number of values of this entry
  

• uint32_t m_offset

  offset of the values in the file
  

• CTiff * m_file

  owner of this entry
  

• std::vector< unsigned char > m_data

Friends

• std::ostream & operator<< (std::ostream &os, const CExifEntry &e)

Classes

• struct Convert

  internal helper function object template More...
  

---

Detailed Description

EXIF data entry in an image file.

this class represents a data entry in a EXIF file.

---

Constructor & Destructor Documentation

CExifEntry (  tag_t  tag, const TagSpace &  tspace )

construct a dummy entry for binary searching with the tag. use only when binary search: iterator it = std::lower_bound( m_entries.begin( ), m_entries.end( ), CExifEntry( tag, tspace ) ) ;

CExifEntry (  tag_t  tag, const TagSpace &  tspace, uint16_t  type, uint32_t  count, uint32_t  offset, CTiff *  file )

initialize the entry with all known values

---

Member Function Documentation

template const double As< double > (  std::size_t  idx = 0  )  const

retrieve the value in the entry as a type T. the data will be converted from the actual type stored in the entry to the requested type T, i.e. there is no undefined behaviour even if the requested type and the actual type is different. Parameters: idx  the index of the value to be retrived. since entry can store multiple instances of values, you need to provide the index of the value you want. T  template parameter to be explicitly specified. it can be one of the following types: uint8_t, uint16_t, uint32_t, int8_t, int16_t, int32_t, Rational<uint32_t>, Rational<int32_t>, double and std::string. Note: when T is std::string, all instances of values in the entry will be formatted to the resulting string. thus "idx" will be ignored. Returns: the converted value of the entry Exceptions: std::runtime_error  when trying to convert a string value to any type other than std::string.

unsigned char * Data (   )

return the raw data read from the file. it will be in the file byte order, not host byte order.

void EnsureDataReady (   )  const [private]

ensure the data is available by reading them from file if needed. do nothing if the data is already ready.

std::string Format (   )  const

returns a formatted string of the value of the entry. this function will translate the value of tag properly according to the type of the tag. Parameters: idx  ignored Returns: the formatted string

bool IsDataReady (   )  const [private]

return true if the data has already been read from file. the Formatted() function will read it if it returns false.

bool IsReference (   )  const [private]

according to the TIFF spec, if the size of the field is less than 4 bytes, the value will be encoded in the offset field. in this case, this function will return false. Returns: return true if the data is stored somewhere in the file pointed by m_offset. return false if the data is stored AS m_offset.

const char * LongName (   )  const

return the long name of the tag. it is a human readable name that can be shown in user interfaces. Returns: name of the tag. the member is static. the caller does not need to free it.

bool operator< (  const CExifEntry &  rhs  )  const

provides a sort order for CExifEntry objects. used in std::map's or binary searches

uint32_t Size (   )  const

size of the data in bytes

tag_t Tag (   )  const

returns the tag ID of the entry. the value of the tag is defined by the EXIF spec.

const char * TagName (   )  const

return the short name of tag. it is an abbeviation without spaces in between. Returns: name of the tag. the member is static. the caller does not need to free it.

---

Friends And Related Function Documentation

std::ostream& operator<< (  std::ostream &  os, const CExifEntry &  e )  [friend]

output a formatted string of the entry to the ostream "os". this function will translate the value of tag properly according to the type of the tag.

---

Member Data Documentation

std::vector<unsigned char> m_data [mutable, private]

cached data. if empty(), data is either not read from file yet or the data is small enough to be packed in m_offset (i.e. IsReference() returns false). it is always in the byte order of the file (i.e. not swapped)

---

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

• src/ExifEntry.hpp
• src/ExifEntry.cpp

---