QExifImageHeader Class Reference
[QtBaseModule]

Detailed Description

The QExifImageHeader class provides functionality for reading and writing EXIF image headers.

EXIF headers are a collection of properties that describe the image they're embedded in. Each property is identified by a tag of which there are three kinds. Image tags which mostly describe the format (dimensions, resolution, orientation) but also include some descriptive information (description, camera make and model, artist). EXIF extended tags which elaborate on some of the image tags and record the camera settings at time of capture among other things. Finally there are GPS tags which record the location the image was captured.

EXIF tags are typically found in JPEG images but may be found in other image formats. To read headers from a JPEG image QExifImageHeader provides the loadFromJpeg() function, and the complementary saveToJpeg() function for writing. To allow reading and writing arbitrary formats QExifImageHeader provides the read() and write() functions which work with just the EXIF header data itself.

Member Type Documentation

enum QExifImageHeader::ExifExtendedTag

Enumerates the extended EXIF tag IDs defined in the EXIF specification.

enum QExifImageHeader::GpsTag

Enumerates the GPS tag IDs from the EXIF specification.

enum QExifImageHeader::ImageTag

Enumerates the TIFF image tag IDs defined in the EXIF specification.

Member Function Documentation

QExifImageHeader::QExifImageHeader ()

Constructs a new EXIF image data editor.

QExifImageHeader::QExifImageHeader ( const QString & fileName )

Constructs a new EXIF image data editor and reads the meta-data from a JPEG image with the given fileName.

QExifImageHeader::~QExifImageHeader ()

Destroys an EXIF image data editor.

QSysInfo::Endian QExifImageHeader::byteOrder () const

Returns the byte order of EXIF file.

void QExifImageHeader::clear ()

Clears all image meta-data.

bool QExifImageHeader::contains ( ImageTag tag ) const

Returns true if an EXIf header contains a value for an image tag and false otherwise.

bool QExifImageHeader::contains ( ExifExtendedTag tag ) const

This is an overloaded member function, provided for convenience.

Returns true if a header contains a a value for an extended EXIF tag and false otherwise.

bool QExifImageHeader::contains ( GpsTag tag ) const

This is an overloaded member function, provided for convenience.

Returns true if an EXIf header contains a value for a GPS tag and false otherwise.

QList<ExifExtendedTag> QExifImageHeader::extendedTags () const

Returns a list of all extended EXIF tags in a header.

QList<GpsTag> QExifImageHeader::gpsTags () const

Returns a list of all GPS tags in an EXIF header.

QList<ImageTag> QExifImageHeader::imageTags () const

Returns a list of all image tags in an EXIF header.

bool QExifImageHeader::loadFromJpeg ( const QString & fileName )

Reads meta-data from a JPEG image with the given fileName.

Returns true if the data was successfully parsed and false otherwise.

bool QExifImageHeader::loadFromJpeg ( QIODevice * device )

This is an overloaded member function, provided for convenience.

Reads meta-data from an I/O device containing a JPEG image.

Returns true if the data was successfully parsed and false otherwise.

bool QExifImageHeader::read ( QIODevice * device )

Reads the contents of an EXIF header from an I/O device.

Returns true if the header was read and false otherwise.

See also loadFromJpeg() and write().

void QExifImageHeader::remove ( ImageTag tag )

Removes the value for an image tag.

void QExifImageHeader::remove ( ExifExtendedTag tag )

This is an overloaded member function, provided for convenience.

Removes the value for an extended EXIF tag.

void QExifImageHeader::remove ( GpsTag tag )

This is an overloaded member function, provided for convenience.

Removes the value for a GPS tag.

bool QExifImageHeader::saveToJpeg ( const QString & fileName ) const

Saves meta-data to a JPEG image with the given fileName.

Returns true if the data was successfully written.

bool QExifImageHeader::saveToJpeg ( QIODevice * device ) const

This is an overloaded member function, provided for convenience.

Save meta-data to the given I/O device.

The device must be non-sequential and already contain a valid JPEG image.

Returns true if the data was successfully written.

void QExifImageHeader::setThumbnail ( const QImage & thumbnail )

Sets the image thumbnail.

See also thumbnail().

void QExifImageHeader::setValue ( ImageTag tag, const QExifValue & value )

Sets the value for an image tag.

See also value().

void QExifImageHeader::setValue ( ExifExtendedTag tag, const QExifValue & value )

This is an overloaded member function, provided for convenience.

Sets the value for an extended EXIF tag.

void QExifImageHeader::setValue ( GpsTag tag, const QExifValue & value )

This is an overloaded member function, provided for convenience.

Sets the value for an GPS tag.

qint64 QExifImageHeader::size () const

Returns the size of EXIF data in bytes.

QImage QExifImageHeader::thumbnail () const

Returns the image thumbnail.

See also setThumbnail().

QExifValue QExifImageHeader::value ( ImageTag tag ) const

Returns the value for an image tag.

See also setValue().

QExifValue QExifImageHeader::value ( ExifExtendedTag tag ) const

This is an overloaded member function, provided for convenience.

Returns the value for an extended EXIF tag.

QExifValue QExifImageHeader::value ( GpsTag tag ) const

This is an overloaded member function, provided for convenience.

Returns the value for a GPS tag.

qint64 QExifImageHeader::write ( QIODevice * device ) const

Writes an EXIF header to an I/O device.

Returns the total number of bytes written.