Tracker Extract Library Reference Manual: XMP

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XMP

XMP — Extensible Metadata Platform (XMP)

Stability Level

Stable, unless otherwise indicated

Functions

TrackerXmpData *	tracker_xmp_new ()
void	tracker_xmp_free ()
gboolean	tracker_xmp_read ()
gboolean	tracker_xmp_apply ()
gboolean	tracker_xmp_apply_regions ()

Types and Values

	TrackerXmpData
	TrackerXmpRegion

Object Hierarchy

Includes

#include <libtracker-extract/tracker-extract.h>

Description

The Adobe Extensible Metadata Platform (XMP) is a standard, created by Adobe Systems Inc., for processing and storing standardized and proprietary information relating to the contents of a file.

XMP standardizes the definition, creation, and processing of extensible metadata. Serialized XMP can be embedded into a significant number of popular file formats, without breaking their readability by non-XMP-aware applications. Embedding metadata ("the truth is in the file") avoids many problems that occur when metadata is stored separately. XMP is used in PDF, photography and photo editing applications.

This API is provided to remove code duplication between extractors using these standards.

Functions

tracker_xmp_new ()

TrackerXmpData *
tracker_xmp_new (const gchar *buffer,
                 gsize len,
                 const gchar *uri);

This function takes len bytes of buffer and runs it through the XMP library.

Parameters

buffer	a chunk of data with xmp data in it.
len	the size of `buffer` .
uri	the URI this is related to.

Returns

a newly allocated TrackerXmpData struct if XMP data was found, NULL otherwise. Free the returned struct with tracker_xmp_free().

Since 0.10

tracker_xmp_free ()

void
tracker_xmp_free (TrackerXmpData *data);

Frees data and all TrackerXmpData members. NULL will produce a a warning.

Parameters

data

a TrackerXmpData struct

Since 0.10

tracker_xmp_read ()

gboolean
tracker_xmp_read (const gchar *buffer,
                  size_t len,
                  const gchar *uri,
                  TrackerXmpData *data);

tracker_xmp_read has been deprecated since version 0.9. and should not be used in newly-written code.

Use tracker_xmp_new() instead.

This function takes len bytes of buffer and runs it through the XMP library. The result is that data is populated with the XMP data found in uri .

Parameters

buffer	a chunk of data with xmp data in it.
len	the size of `buffer` .
uri	the URI this is related to.
data	a pointer to a TrackerXmpData structure to populate.

Returns

TRUE if the data was populated successfully, otherwise FALSE is returned.

Since 0.8

tracker_xmp_apply ()

gboolean
tracker_xmp_apply (TrackerSparqlBuilder *preupdate,
                   TrackerSparqlBuilder *metadata,
                   const gchar *graph,
                   GString *where,
                   const gchar *uri,
                   TrackerXmpData *data);

This function applies all data in data to metadata .

The graph parameter was added in 0.12.

This function also calls tracker_xmp_apply_regions(), so there is no need to call both functions.

Parameters

preupdate	the preupdate object to apply XMP data to.
metadata	the metadata object to apply XMP data to.
graph	the graph to apply XMP data to.
where	the where object.
uri	the URI this is related to.
data	the data to push into `metadata` .

Returns

TRUE if the data was applied to metadata successfully, otherwise FALSE is returned.

Since 0.8

tracker_xmp_apply_regions ()

gboolean
tracker_xmp_apply_regions (TrackerSparqlBuilder *preupdate,
                           TrackerSparqlBuilder *metadata,
                           const gchar *graph,
                           TrackerXmpData *data);

This function applies all regional data to preupdate and metadata . Regional data exists for image formats like JPEG, PNG, etc. where parts of the image refer to areas of interest. This can be people's faces, places to focus, barcodes, etc. The regional data describes the title, height, width, X, Y and can occur multiple times in a given file.

This data usually is standardized between image formats and that's what makes this function different to tracker_xmp_apply() which is useful for XMP files only.

Parameters

preupdate	the preupdate object to apply XMP data to.
metadata	the metadata object to apply XMP data to.
graph	the graph to apply XMP data to.
data	the data to push into `preupdate` and `metadata` .

Returns

TRUE if the data was applied to preupdate and metadata successfully, otherwise FALSE is returned.

Since 0.12

Types and Values

TrackerXmpData

typedef struct {
	/* NS_DC */
	gchar *title;
	gchar *rights;
	gchar *creator;
	gchar *description;
	gchar *date;
	gchar *keywords;
	gchar *subject;
	gchar *publisher;
	gchar *contributor;
	gchar *type;
	gchar *format;
	gchar *identifier;
	gchar *source;
	gchar *language;
	gchar *relation;
	gchar *coverage;

	/* NS_CC */
	gchar *license;

	/* NS_PDF */
	gchar *pdf_title;
	gchar *pdf_keywords;

	/* NS_EXIF */
	gchar *title2;
	gchar *time_original;
	gchar *artist;
	gchar *make;
	gchar *model;
	gchar *orientation;
	gchar *flash;
	gchar *metering_mode;
	gchar *exposure_time;
	gchar *fnumber;
	gchar *focal_length;
	gchar *iso_speed_ratings;
	gchar *white_balance;
	gchar *copyright;

	/* TODO NS_XAP*/
	gchar *rating;

	/* TODO NS_IPTC4XMP */
	/* TODO NS_PHOTOSHOP */
	gchar *address;
	gchar *country;
	gchar *state;
	gchar *city;

	/* ABI barrier (don't change things above this) */
	gchar *gps_altitude;
	gchar *gps_altitude_ref;
	gchar *gps_latitude;
	gchar *gps_longitude;
	gchar *gps_direction;

	/* List of TrackerXmpRegion */
	GSList *regions;
} TrackerXmpData;

Structure defining XMP data of a given file.

Members

gchar *`title`;	Value for the dc:title property.
gchar *`rights`;	Value for the dc:rights property.
gchar *`creator`;	Value for the dc:creator property.
gchar *`description`;	Value for the dc:description property.
gchar *`date`;	Value for the dc:date property.
gchar *`keywords`;	Value for the dc:keywords property.
gchar *`subject`;	Value for the dc:subject property.
gchar *`publisher`;	Value for the dc:publisher property.
gchar *`contributor`;	Value for the dc:contributor property.
gchar *`type`;	Value for the dc:type property.
gchar *`format`;	Value for the dc:format property.
gchar *`identifier`;	Value for the dc:identifier property.
gchar *`source`;	Value for the dc:source property.
gchar *`language`;	Value for the dc:language property.
gchar *`relation`;	Value for the dc:relation property.
gchar *`coverage`;	Value for the dc:coverage property.
gchar *`license`;	Value for the nie:license property.
gchar *`pdf_title`;	Title of the PDF.
gchar *`pdf_keywords`;	Keywords in the PDF.
gchar *`title2`;	Title from the EXIF data.
gchar *`time_original`;	Original time from the EXIF data.
gchar *`artist`;	Artist from the EXIF data.
gchar *`make`;	Make info from the EXIF data.
gchar *`model`;	Model from the EXIF data.
gchar *`orientation`;	Orientation info from the EXIF data.
gchar *`flash`;	Flash info from the EXIF data.
gchar *`metering_mode`;	Metering mode from the EXIF data.
gchar *`exposure_time`;	Exposure time from the EXIF data.
gchar *`fnumber`;	Focal ratio from the EXIF data.
gchar *`focal_length`;	Focal length from the EXIF data.
gchar *`iso_speed_ratings`;	ISO speed ratings from the EXIF data.
gchar *`white_balance`;	White balance info from the EXIF data.
gchar *`copyright`;	Copyright info from the EXIF data.
gchar *`rating`;	Rating.
gchar *`address`;	Address.
gchar *`country`;	Country.
gchar *`state`;	State.
gchar *`city`;	City.
gchar *`gps_altitude`;	GPS altitude.
gchar *`gps_altitude_ref`;	GPS altitude reference.
gchar *`gps_latitude`;	GPS latitude.
gchar *`gps_longitude`;	GPS longitude.
gchar *`gps_direction`;	GPS direction information.
GSList *`regions`;	List of TrackerXmpRegion items.

TrackerXmpRegion

typedef struct {
	gchar *title;
	gchar *description;
	gchar *type;
	gchar *x;
	gchar *y;
	gchar *width;
	gchar *height;
	gchar *link_class;
	gchar *link_uri;
} TrackerXmpRegion;

Structure defining data of a given region in a TrackerXmpData.

Members

gchar *`title`;	Title of the region.
gchar *`description`;	Description of the region.
gchar *`type`;	Type of the region.
gchar *`x`;	X axis position.
gchar *`y`;	Y axis position.
gchar *`width`;	Width.
gchar *`height`;	Height.
gchar *`link_class`;	Link class.
gchar *`link_uri`;	Link URI.