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November 30, 2009

How XMP is used in Annotate

Our Annotate software uses the XMP (eXtensible Meta Platform) notation that was developed by Adobe back in 2001 to store the coordinate-bound annotations (comments) and virtual crop information in a non-destructible way in an image.

XMP metadata can be embedded into almost any file format that is being used today. Annotate V1.10 stores the XMP information into the JPG file's header and future releases will support NEF and other raw formats as well, storing the meta data with the same XMP data structure.

You may already be using XMP to store metadata in your image withouth even knowing it -- if you are adding keywords to your photographs, these are written using the IPTC Core schema in XMP format.

XMP allows anybody to extend it by declaring so called "schemas" describing the structure of the stored data. There is a range of photo editing software that is already using XMP to store metadata, and that is aware of some of the existing schemas (the currently supported schemas include Dublin Core & Extension, IPTC Core and PLUS)

Some catalogs and editing software are storing metadata using sidecar .xmp files that are stored next to your jpeg/raw images. These sidecar files contain the metadata describing the image, but they can get lost if you move the image, send it to someone via email or upload the image to a web gallery.

When developing Annotate, we have extended the XMP schema to be able store metadata about the image bound to coordinates. This way, the annotations you make using Annotate are stored as XMP image metadata in the same way as the keywords or tags you make in your favorite image workflow software.

The main difference between keywords and annotations is that annotations are bound to coordinates, while tags describe an image as a whole. You can think about annotations as keywords bound to coordinates.

Annotate stores XMP metadata describing the annotations directly in the image (as opposed to sidecar .xmp files). When you e.g. share an image with your friend by sending it to him via email, the meta data is kept inside the file. It is possible to send an email directly from Annotate. To learn how, see our wiki on how to send images via email.

The approach of storing your comments in the image in XMP format has many advantages. The annotations are non destructive: Your original image is unchanged. Furthermore, as opposed to drawings made in Photoshop, annotations are included in your images as text. And text can be processed by your computer. For example, a computer can quickly search for specific annotations in large volumes of your image catalogue.

An example: Someone is annotating a photograph with 10 people in it. Using keywords you would only enumerate the people, while annotations will identify the persons accurately. When you are searching based on keywords, you will find the photograph, but you may not know who is who. When searching in annotations, you will find the image and immediately know who is who in the photograph.

A search feature will come in a future version of Annotate, but you can start annotating your image collection right now.

Posted by bgs at November 30, 2009 4:16 PM