exiv2/doc/templates/__intro__

<h2><a href="namespaces.html">Namespaces</a></h2>

<p>The <a href="index.html">Exiv2 library</a> is made up of all
elements defined in the <a href="namespaceExiv2.html">Exiv2
namespace</a>.</p>

<h2><a href="classes.html">Classes</a></h2>

<p>The top-level class of the Exiv2 library is <a class="el"
href="classExiv2_1_1Image.html">Exiv2::Image</a>.  Exiv2::Image
defines the interface to access image metadata.  Derived from
Exiv2::Image are implementations for different image formats. Most
importantly, they contain the logic to read metadata from the image
into Exiv2 metadata containers and write it back to the image.
Most applications will use
<a class="el" href="classExiv2_1_1ImageFactory.html">Exiv2::ImageFactory</a> 
to access images in files or memory, in which case the image format 
is transparent to them. The factory determines the image format from the
data (not the file extension) and creates an object of the corresponding
Image subclass.</p>

<p>Exif and IPTC metadata is manipulated through the classes
<a class="el" href="classExiv2_1_1ExifData.html">Exiv2::ExifData</a> 
and <a class="el" href="classExiv2_1_1IptcData.html">Exiv2::IptcData</a>.
They hold a container of Exif and IPTC metadata, respectively, and define
related methods to access and manipulate the metadata.
<br>
Exif tag and IPTC dataset reference information for the standard tags
and datasets is available in the two static classes
<a class="el" href="classExiv2_1_1ExifTags.html">Exiv2::ExifTags</a> and
<a class="el" href="classExiv2_1_1IptcDataSets.html">Exiv2::IptcDataSets</a>.
<br>
The metadata containers hold objects derived from
<a class="el" href="classExiv2_1_1Metadatum.html">Exiv2::Metadatum</a>.
Interface class Exiv2::Metadatum defines methods to access the
information of one metadatum. It models the tag data as a key and
value pair.
The abstract base class 
<a class="el" href="classExiv2_1_1Key.html">Exiv2::Key</a> defines the 
interface for a key. Concrete keys implement Exif and IPTC keys.
The abstract base class 
<a class="el" href="classExiv2_1_1Value.html">Exiv2::Value</a> defines 
the interface to access tag information, from which concrete values are
derived. The actual value used in a metadatum depends on the type of
the Exif tag or IPTC dataset. It is usually determined when the Exif or
IPTC metadata is read from an image. It is also possible to manually create
a Value and together with a key add it to an ExifData or IptcData 
container.</p>

The classes to access XMP metadata are 
<a class="el" href="classExiv2_1_1XmpData.html">Exiv2::XmpData</a>,
<a class="el" href="classExiv2_1_1Xmpdatum.html">Exiv2::Xmpdatum</a> 
and <a class="el" href="classExiv2_1_1XmpKey.html">Exiv2::XmpKey</a>.
They work similar to the corresponding Exif and IPTC classes.
The property reference information is in
<a class="el" href="classExiv2_1_1XmpProperties.html">Exiv2::XmpProperties</a>.
In addition to the expected new members, class
<a class="el" href="classExiv2_1_1Image.html">Exiv2::Image</a>
now also has an interface to access the raw XMP packet.
<br>
All XMP value types are supported: Simple types, structures,
arrays, property qualifiers and language alternatives.
<br>
XMP properties are accessed through keys of the form
"Xmp.&lt;Prefix&gt;.&lt;PropertyPath&gt;", where &lt;Prefix&gt; is the preferred 
(or rather, registered) prefix for a schema namespace and 
&lt;PropertyPath&gt; is the path of the XMP node. In its most basic
form, to address simple properties, &lt;PropertyPath&gt; is the name
of the property. In general, &lt;PropertyPath&gt; can be used to 
address any XMP node, including array items, structure fields
qualifiers and deeply nested properties.
<br>
Any properties in known namespaces are supported and additional
namespaces can be registered.
<br>
The specialized Exiv2 values 
<a class="el" href="classExiv2_1_1XmpTextValue.html">Exiv2::XmpTextValue</a>,
<a class="el" href="classExiv2_1_1XmpArrayValue.html">Exiv2::XmpArrayValue</a>
and <a class="el" href="classExiv2_1_1LangAltValue.html">Exiv2::LangAltValue</a> are
provided to simplify the use of XMP properties.
<br>
Note: Unlike Exif and IPTC tags, XMP properties do not have
a tag number.

<h2><a href="examples.html">Examples</a></h2>

<p>There are several simple examples that demonstrate the basic use of Exiv2
functionality: <a href="exifprint_8cpp-example.html">Exifprint</a> 
shows how the Exif data of an image can be read and written to the screen.
<a href="iptcprint_8cpp-example.html">Iptcprint</a> is a similar 
example to print IPTC data.
<a href="addmoddel_8cpp-example.html">Addmoddel</a> shows how to
add, modify and delete Exif metadata. 
<a href="exifcomment_8cpp-example.html">Exifcomment</a> shows how to
set the exif comment of an image. 
<a href="xmpsample_8cpp-example.html">Xmpsample.cpp</a> contains examples
of how to set various types of XMP properties.
<br>
For more real-world code have a look at the implementation of the
different actions of the Exiv2 utility (actions.cpp).</p>

<h2><a href="makernote.html">Makernotes</a></h2>

<p>Exif Makernote data can be accessed through ExifData in the same
way as the standard Exif tags. In other words, for each entry of a
known Makernote, there is a corresponding Metadatum in the ExifData
container. Makernote taglists are internally kept in classes
Exiv2::Internal::&lt;Make&gt;MakerNote (e.g.,
<a class="el" href="classExiv2_1_1Internal_1_1CanonMakerNote.html">
Exiv2::Internal::CanonMakerNote</a>.)