Image thumbnails are automatically created when an image is added. These can then be changed and/or deleted through the Entry->Edit Properties page. The Edit properties page also allows you to specify whether the image should be scaled down. Any entry, not just images, can also have a thumbnail associated with through the Entry->Add Properties form. Image entries support a set of Image Change functions through the Entry->Edit->Change Image menu. One can resize the image, convert it to gray scale or create or regenerate the thumbnail image at a certain width. Thumbnails can be created for any number of Image entries through the Entry->Edit->Extended Edit facilities.

• Go to an image entry or a folder that contains image entries.
• From the Extended Edit page open the Process with Javascript section.
• Under the "Image" tab on the right select the "entry.makeThumbnail". This adds the command into the command list
• The first argument says to delete any existing thumbnail image
• The second argument is the width
• Note - You can optionally select an entry type (e.g. Image)
• Press Apply Javascript

This will run through each entry in turn and create a new thumbnail image.
Note: this will also work with PDF entries. The default width of a thumbnail image is 600. This can be changed by setting the below property in a .properties file, e.g.:

ramadda.thumbnail.width=800

This can also be set directly through the Admin interface: