I see quite a few people that experience issues with ImageMagick, either immediately after install/setup, or if their hosting environment changes certain settings.
Is there currently any known way to reprocess original media uploaded to Omeka?
Unrelated: Out of curiosity, what was the design decision to use ImageMagick over PHP's GD library? Was it a PHP memory consumption issue?
The Image Resize plugin does just this: it runs through all the files and reprocesses them with ImageMagick.
The original intent of the plugin, and the reason for the name, was to update thumbnails when an admin picks new size constraints, but it accomplishes this by re-running ImageMagick on them.
Note, this plugin doesn't yet have a 2.0-compatible released version yet.
As for why we picked ImageMagick, there are many reasons. Memory consumption is definitely one of them, and another is that ImageMagick supports a much larger array of input files than GD does.
Thank you, John! I'll take a look at the Image Resize plugin and maybe I'll make that my first attempt at "creating" (updating) an Omeka plugin for 2.0.