Changes for online API documentation.
Andreas Huggel
18 years ago
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<h2><a href="namespaces.html">Namespaces</a></h2>
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<p>The <a href="index.html">Exiv2 library</a> is made up of all
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elements defined in the <a href="namespaceExiv2.html">Exiv2
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namespace</a>. The Action and Util namespaces are only used by the
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Exiv2 command line utility.</p>
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<h2><a href="classes.html">Classes</a></h2>
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<p>The top-level class of the Exiv2 library is
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<a class="el" href="classExiv2_1_1Image.html">Exiv2::Image</a>
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(don't let the components diagram below mislead you). Exiv2::Image
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defines the interface to access various image metadata. Derived from
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Exiv2::Image are the implementations of different image formats. Most
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applications will use
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<a class="el" href="classExiv2_1_1ImageFactory.html">Exiv2::ImageFactory</a>
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to access images in files or memory, in which case the image format
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is transparent to them.</p>
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<p>Exif and IPTC metadata is manipulated through the classes
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<a class="el" href="classExiv2_1_1ExifData.html">Exiv2::ExifData</a>
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and <a class="el" href="classExiv2_1_1IptcData.html">Exiv2::IptcData</a>.
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They hold a container of Exif and IPTC metadata, respectively, and define
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related methods to access and manipulate the metadata. The containers hold
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objects derived from
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<a class="el" href="classExiv2_1_1Metadatum.html">Exiv2::Metadatum</a>.
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Interface class Exiv2::Metadatum defines methods to access the
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information of one Exif tag or IPTC dataset. It models the tag data as
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a key and value pair.
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The abstract base class
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<a class="el" href="classExiv2_1_1Key.html">Exiv2::Key</a> defines the
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interface for a key. Concrete keys implement Exif and IPTC keys.
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The abstract base class
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<a class="el" href="classExiv2_1_1Value.html">Exiv2::Value</a> defines
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the interface to access tag information, from which concrete values are
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derived. The actual value used in a metadatum depends on the type of
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the Exif tag or IPTC dataset. It is usually determined when the Exif metadata
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is read from an image. It is also possible to manually create a Value and
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together with a key add it to an ExifData or IptcData container.</p>
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Top-level Exiv2 classes to access XMP metadata are
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<a class="el" href="classExiv2_1_1XmpData.html">Exiv2::XmpData</a>,
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<a class="el" href="classExiv2_1_1Xmpdatum.html">Exiv2::Xmpdatum</a>
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and <a class="el" href="classExiv2_1_1XmpKey.html">Exiv2::XmpKey</a>.
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They work similar to the corresponding Exif and IPTC classes.
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The property-repository is <a class="el" href="classExiv2_1_1XmpProperties.html">Exiv2::XmpProperties</a>.
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In addition to the expected new members, class
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<a class="el" href="classExiv2_1_1Image.html">Exiv2::Image</a>
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also has an interface to access the raw XMP packet.
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All XMP value types are supported: Simple types, structures,
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arrays, property qualifiers and language alternatives.
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XMP properties are accessed through keys of the form
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"Xmp.<Prefix>.<PropertyPath>", where <Prefix> is the preferred
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(or rather, registered) prefix for a schema namespace and
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<PropertyPath> is the path of the XMP node. In its most basic
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form, to address simple properties, <PropertyPath> is the name
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of the property. In general, <PropertyPath> can be used to
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address any XMP node, including array items, structure fields
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qualifiers and deeply nested properties.
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Any properties in known namespaces are supported and additional
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namespaces can be registered.
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The specialized Exiv2 values
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<a class="el" href="classExiv2_1_1XmpTextValue.html">Exiv2::XmpTextValue</a>,
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<a class="el" href="classExiv2_1_1XmpArrayValue.html">Exiv2::XmpArrayValue</a>
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and <a class="el" href="classExiv2_1_1LangAltValue.html">Exiv2::LangAltValue</a> are
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provided to simplify the use of XMP properties.
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Note: Unlike Exif and IPTC tags, XMP properties do not have
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a tag number.
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<h2><a href="examples.html">Examples</a></h2>
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<p>There are several simple examples that demonstrate the basic use of Exiv2
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functionality: <a href="exifprint_8cpp-example.html">Exifprint</a>
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shows how the Exif data of an image can be read and written to the screen.
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<a href="iptcprint_8cpp-example.html">Iptcprint</a> is a similar
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example to print IPTC data.
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<a href="addmoddel_8cpp-example.html">Addmoddel</a> shows how to
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add, modify and delete Exif metadata.
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<a href="exifcomment_8cpp-example.html">Exifcomment</a> shows how to
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set the exif comment of an image.
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<a href="xmpsample_8cpp-example.html">Xmpsample.cpp</a> contains examples
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of how to set various types of XMP properties.<br>
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For more real-world code have a look at the implementation of the
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different actions of the Exiv2 utility (actions.cpp).</p>
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<h2><a href="makernote.html">Makernotes</a></h2>
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<p>Exif Makernote data can be accessed through ExifData in the same
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way as the standard Exif tags. In other words, for each entry of a
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known Makernote, there is a corresponding Metadatum in the ExifData
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container. The abstract base class
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<a class="el" href="classExiv2_1_1MakerNote.html">Exiv2::MakerNote</a> defines
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the Makernote interface. Subclass
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<a class="el" href="classExiv2_1_1IfdMakerNote.html">Exiv2::IfdMakerNote</a>
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models makernotes encoded in IFD format.
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<a href="classExiv2_1_1MakerNote.html#_details">Implementing a new
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IFD makernote</a> is straightforward. Implementing a new makernote that is not
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encoded in IFD format however, is more difficult. Please
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<a href="mailto:ahuggel@gmx.net"> contact me</a> if you have such a
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makernote specification and would like assistance adding it to Exiv2.</p>
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<h2><a class="anchor">IFD (Image File Directory)</a></h2>
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<p><a class="el" href="classExiv2_1_1Ifd.html">Exiv2::Ifd</a> is a generic
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low-level class that models an image file directory as defined by TIFF
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and used in the Exif standard. Exiv2::Ifd could be used to implement
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read only as well as read/write access to Exif (or TIFF) data without
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the overhead (and convenience) of Exiv2::ExifData.</p>
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<h2><a class="anchor">Components</a></h2>
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<p>The picture below shows the components that make up the Exiv2
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library and how they depend on each other. Component names are the
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same as the basenames of their source files. Each component has its
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own header and source files.</p>
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<center>
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<h3><a class="anchor">Exiv2 Components Diagram</a></h3>
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<p><img src="../include/exiv2-components.png" width="660" height="543" alt="Exiv2 components diagram"></p>
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</center>
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<p> </p>
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