Guidelines for Derived JPEG Thumbnail Images
These Guidelines indicate requirements for web-deliverable thumbnail JPEG image files created for PALMM Visual Collections projects. JPEG thumbnails correspond to larger display images in JPEG 2000 or SID scaleable format.


File Format:

JPEG (Joint Photographic Expert Group)
Specification: ISO 10918-1/2




Minimum (highest image quality)
Not greater than 15% (image quality not less than 85% of source file)


Same as source file


Same as source file

Image Dimensions:

Width = 100 pixels; Height = variable
Maintain original image aspect ratio
Note: JPEG Thumbnails for PALMM Visual Collections are used by patrons to select larger, zoomable images. For this reason, the thumbnail may highlight a significant aspect of the larger image rather than the entire image in totality.

Interpolation: Resample
File Header: Append structured information about the derivation process as appropriate to the SUSDL XML Metadata DTD (forthcoming)
A structured information template will be added in a future revision of these Guidelines

No single method of processing is recommended. 

Quality Control:
A visual inspection together with a query of the file header should be completed by spot check.  Spot check requires inspection of every image in thumbnail view and of no less than 10% of the images in full-image view.
A variety of factors effecting on-screen and print legibility should be examined.  For additional guidance, we  recommend reading Cornell University's Digital Imaging Tutorial: Quality Control.