Display Metadata on Web Page Use Case
Embedded Metadata of a photo is perceived by many people as being invisible. At first sight this is right as when the pixels of a digital image are rendered by photo software or by a web browser nobody can see a rendition of the metadata too.
But if the metadata are embedded in an image file it is not a big challenge to display it on a web page side-by-side with the rendition of the pixels. The big advantage of doing this is the support of the Search Engine Optimization of a web page. As search engines prefer text which is visible to the end user over invisible data it is quite obvious that displaying metadata fields like the caption, the name of the photographer, the location where the picture was taken and a copyright notice has a more direct impact on what is indexed than metadata embedded into the image file.
So let's investigate how metadata values can be displayed - first in generic terms:
1) Use a software that can read the embedded metadata and can write the retrieved values to a temporary file.
2) Create a template for the web page which should show the photo and its metadata. Include placeholders for the metadata fields which should be displayed.
3) Use a software that can read the web page template and which can replace the placeholders by the values from the temporary file, see step 1, and which can finally write this individualized instance of the web page as a file.
This approach has been used to create the Support Gallery of Images of this Embedded Metadata site. People are invited to send in an image with embedded metadata by email - more details can be found on this page.
When a photo is received by the IPTC office it is processed this way:
a) Retrieve the metadata by the ExifTool, created and maintained by Phil Harvey. It not only retrieves Exif metadata but also the IPTC Core and Extension fields in the IPTC IIM and the XMP formats. The output of ExifTool is saved as XML file.
b) A script resizes the photo to a maximum width or height for the individual web page and creates a small thumbnail for the overview page.
c) An XSLT file provides a template for the web page which shows the individual photo in a news story like context using a subset of metadata fields. In addition the page shows a table of all IPTC Core and Extension fields which were found in the photo. When this XSLT is run by an XSLT processor it inserts the corresponding metadata values from the ExifTool output file into this web page template. The result is an individualized web page for each photo.
d) Finally a script collects all available photos and generates an overview page (the home page of the Support Gallery of Images), from it the user can select and display any single image.
Note: the whole procedure is controlled by a Windows PowerShell 2.0 script.
The IPTC office plans to provide a simple and generic version of this generator for displaying embedded metadata on a web page in a package that can be run on a Windows PC in January 2012.
Footnote: This approach could be used for media of other media types like audio or video too. The big challenge for implementing such a generic tool for audio and video is the lack of a shared set of metadata and a common technology to embed them regardless of the file type. The IPTC office currently investigates an audio and video implementation.