exif2rdf - reads Exif meta data from files then prints or stores as RDF statements
Using ExifTool and Redland RDF Libraries.
exif2rdf [-c config] [-b base_uri] [-s syntax] file...
exif2rdf [-c config] [-b base_uri] -p path [-n|-u] file...
exif2rdf [-c config] -d
exif2rdf -h
-b|--base_uri set base URI, must be absolute HTTP,
default is http://www.theflints.net.nz/
-c|--config load configuration from file
-d|--dump print current configuration
-h|--help print help
-n|--new create new database, default
-p|--path path of RDF database to store statements
-s|--syntax serialize statements in RDF syntax,
for example turtle or rdfxml-abbrev,
default is ntriples.
For a list of possible values
run the Redland serializer utility
"rapper --help" and see output FORMATs.
-u|--update update existing database
file containing Exif meta data
This class, RDF::Redland::Model::ExifTool , extends the Redland model or set of RDF statements (RDF::Redland::Model) to read Exif meta data from instances of ExifTool (Image::ExifTool). This document explains how to use the class through the example script exif2rdf .
Exif meta data is in tag and value pairs, for example:
Aperture 4.0
RDF is in subject, predicate (verb) and object triples called statements, for example:
<file://.../t/data/lighthouse.jpg>; <http://...#apertureValue>; "4.0" .
This class can:
translate an Exif tag and its value into an RDF statement
parse RDF statements from the values of Exif tags
The following sections give examples of translating and parsing Exif into RDF. Those examples serialize or print RDF, the final one stores RDF in a database. The final section explains how to find out more.
Let's get some meta data from an image by running the script on one of the test images in this class' distribution:
exif2rdf t/data/lighthouse.jpg
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#focalLengthIn35mmFilm>; "6.3 mm" .
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#ISOSpeedRatings>; "100" .
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#apertureValue>; "5.6" .
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#shutterSpeedValue>; "1/1200" .
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#make>; "FUJIFILM" .
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#model>; "FinePix S5600" .
<file://.../t/data/lighthouse.jpg>; <http://www.w3.org/2003/12/exif/ns#dateTimeOriginal>; "2009-01-19T11:37:53" .
The RDF statements, in ntriples syntax, contains meta data from the camera: exposure, camera model and when the image was taken.
Here's how it works. First the script creates an instance of this class, a model or container for RDF statements. Then the class creates a subject URI from the image file's full path name. The TranslateTag hash in the class' configuration maps an Exif tag name to the equivalent RDF predicate URI. The class tries to translate each tag into a predicate. If successful an RDF statement is created from the subject and predicate with the tag's value as the object. Otherwise the tag is ignored. Finally the script serializes or prints out all the statements in the model.
All the examples in this tutorial use the default configuration which can be replaced.
People can add their own meta data to images with Exif tags including Artist, ImageDescription and Comment. Let's try another image:
exif2rdf t/data/ship.jpg
<file://.../tutorial/ship.jpg>; <http://www.w3.org/2003/12/exif/ns#imageDescription>; "a model container ship made of Lego" .
<file://.../tutorial/ship.jpg>; <http://www.w3.org/2003/12/exif/ns#artist>; "Andrew Flint" .
...camera meta data...
The human meta data describes the image and names the artist!
This class can only read meta data from an image, use ExifTool to add or update.
Both exif2rdf and exiftool -X translate but only exif2rdf can parse meta data from the values of Exif tags.
The human meta data in the last image was plain old text. But the next image has RDF statements in the value of the Comment tag. Try:
exif2rdf --syntax turtle t/data/family.jpg
<file://.../t/data/family.jpg>;
<http://purl.org/dc/terms/description>; "family eating fish and chip lunch by the beach" ;
<http://purl.org/dc/terms/spatial>; "Raumati South, Wellington, NZ" ;
<http://xmlns.com/foaf/0.1/depicts>; (
<http://www.theflints.net.nz/gregory/about#me>;
<http://www.theflints.net.nz/alison/about#me>;
<http://www.theflints.net.nz/russell/about#me>;
<http://www.theflints.net.nz/oliver/about#me>;
) ;
<http://xmlns.com/foaf/0.1/maker>; <http://www.theflints.net.nz/andrew/about#me>; .
<http://www.w3.org/2003/12/exif/ns#ISOSpeedRatings>; "50" ;
<http://www.w3.org/2003/12/exif/ns#apertureValue>; "4.5" ;
...more camera meta data...
This time there is a wider range of human meta data, in the turtle syntax, including who appears in the image and where it was taken. The human and camera meta data are simply merged.
In the configuration, ParseTag lists the Exif tags to check for statements and ParseSyntax lists the RDF syntax to parse with. If a value does not contain RDF that tag is translated instead.
So far the RDF statements have been serialized or printed. This time the statements will be stored in a database. Try:
exif2rdf --path exif_meta_data t/data/lighthouse.jpg t/data/ship.jpg t/data/family.jpg
This creates a set of database files, in the current directory, called exif_meta_data-*.db , containing the meta data from all the images in this tutorial. To serialize with Redland RDF try:
rdfproc exif_meta_data serialize turtle
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>; .
<file://.../t/data/ship.jpg>;
...
<file://.../t/data/family.jpg>;
...
<file://.../t/data/lighthouse.jpg>;
...
this example script by running exif2rdf --help or looking at the code
this class the RDF::Redland::Model::ExifTool manpage and its Configuration
ExifTool the Image::ExifTool manpage
Redland RDF Libraries Perl interface http://librdf.org/docs/perl.html including querying and reasoning with RDF databases
Copyright 2008-2010 Andrew Flint, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.