Generating thumbnails
A thumbnail is a small bitmap image of the first page of a content element. Using thumbnails allows users to quickly verify content before they download or check out documents.
The Content Platform Engine includes a thumbnail generation service for rendering thumbnail images automatically. This service renders a thumbnail image from a document content element. Thumbnails cannot be generated for annotations.
Thumbnails can also be user-generated; that is, the thumbnail images are generated by a third-party application rather than the thumbnail generation service integrated with the server. User-generated thumbnail images are associated with documents and persisted on the Content Platform Engine.
- The Thumbnail Extension Add-on is required for Content Platform Engine thumbnail generation. The add-on is not required for persisting user-generated thumbnails.
- The thumbnail generation process runs outside of the Content Platform Engine Java™ virtual machine (JVM) and uses additional memory. For information about managing the thumbnail generation process, see Tuning Content Platform Engine thumbnail performance.
The Thumbnail Extensions Add-On creates an instance of the "Thumbnail Request Sweep", a queue sweep that processes thumbnail request objects in the ThumbnailRequest table. Thumbnail format, size, and color parameters are configured in the sweep. The default sweep instance is configured to be efficiently continuous. It runs in a wait state until it is notified that a new request is posted.
The queue sweep interacts with IBM® Outside In Image Export, which renders thumbnail images for the first page of documents. A thumbnail object is created that contains the thumbnail image. The object also references the source document and the content element for the generated image.
The system removes successfully completed thumbnail requests from the ThumbnailRequest queue table. It also removes failed requests that cannot be fixed by an administrator, such as non-existent content or source document, or attempts to overwrite a user-generated thumbnail. Failed requests that are fixable by an administrator are automatically tried again up to a configurable number of times. If the retries fail, the requests remain in the queue table. A thumbnail request object provides failure information, and allows an administrator to manually restart retries for failed requests.
Thumbnail request options
| Event-based generation | The class subscription, "Default Thumbnail Generation Subscription", creates thumbnail requests for new documents. |
|---|---|
| Sweep-based generation | A thumbnail generation job sweep creates thumbnail requests for existing documents. You can create one or more thumbnail generation jobs. |
| Ad hoc generation | In ad hoc generation, the user creates a thumbnail request for a particular document. Unlike
event-based and sweep-based generation, ad hoc generation is not limited
to the first content element in a document version. For example, the user
can request two thumbnails for a document version by specifying two
different content elements in the document version.
You can use the administrator console to create a thumbnail request for a document. From the object store navigation pane, open the document for which you want to create a thumbnail. In the details pane, click the Content Elements tab. Select a content element, click Thumbnail and select Add. |