Extensible Metadata Platform (XMP) is an XML-based standard for storage and interchange of metadata, developed by Adobe Systems Inc. The standard defines the rules for storage and processing of the metadata, and provides a number of schemas for storage of information that is typically associated with images and documents, such as Title, Author, Creation date/time, Rating, etc. Applications can add their own schemas to store arbitrary information.

XMP metadata can be attached to files of various formats, such as TIFF, JPEG, PSD and PDF, or stored as a standalone file.

ImageGear provides the following ways for working with XMP metadata:

• Accessing XMP properties via the ImageGear Metadata API. In this mode, ImageGear decodes XMP properties and sends them to the application via metadata callbacks.
• Working with unprocessed XMP metadata. In this mode, ImageGear passes XMP to the application as a byte array, treating it as a single tag of the containing metadata format.

By default, ImageGear parses the XMP stream into its metadata structure, and does not provide the Raw XMP stream. If you don't want ImageGear to parse the XMP stream, and prefer to instead access the unprocessed XMP stream, set global control parameter XMP.Parse to FALSE.

During saving, if XMP.Parse is TRUE, ImageGear expects a tree under the XMP tag, and serializes this tree into the output file. If XMP.Parse is FALSE, ImageGear expects a byte array in the XMP tag, and saves it verbatim to the file.

Since the XMP standard identifies schema properties using string names, rather than numbers, ImageGear also uses names to identify XMP properties. However, it uses numeric identifiers to differentiate between the kinds of entities, such as Description (schema), Array, Property, Qualifier, etc. All properties have ID = ImGearXMPTagIDs.Property, but differ by their names.

See XMP Non-Image Data Structure for a description of XMP metadata structure in ImageGear.

Example:

Representation of XMP metadata tree.

• XMP
  • http://ns.adobe.com/xap/1.0/
    • About = ""
    • Namespace
      • Prefix = "xmp"
      • URI = "http://ns.adobe.com/xap/1.0/"
    • Properties
      • xap:Rating
        • Value = 4
      • xap:Identifier
        • Value = "1234.0345.34532.234231"
  • http://purl.org/dc/elements/1.1/
  • Namespace
    • Prefix = "dc"
    • URI = http://purl.org/dc/elements/1.1/
  • Properties
    • dc:subject
      • Bag
    • Item
      • Value = "Test subject 1"
    • Item
      • Value = "Test subject 2"
    • dc:title
      • Alt
    • Item
      • Lang = "x-default"
      • Value = "XMP Support Specification"