The ImageMagick Preview Server plug-in uses ImageMagick (and optionally Ghostscript) to generate previews from uploaded native files.
Note: Whether or not the image preview generation is actually handled by the plug-in depends on wether or not an image preview is already provided by the client application:
Uploading large images could lead to a heavy CPU load. Make sure that you have enough CPU power available on the server machine, or even set up a dedicated application server for this task and, for example, let photographers upload to it.
Tip: Alternatively, you can disable the ImageMagick Server plug-in and have no previews generated for uploaded PSD, PDF, AI, or EPS files. You could enable the PHP Preview and Metadata Server plug-in (enabled by default) to still have previews generated for JPG, GIF, or PNG files, which runs through PHP’s GD library and is a much lighter task.
However, this requires extra memory to be configured for the PHP processes and large images could run PHP out of memory which would block the image upload. For example, a 15 megapixel 24 bit RGB JPEG image takes roughly 10 MB to upload and 15 x (24/8) = 45 MB to extract (in PHP) before it can be processed.
For Mac OS X, a better choice is to use the Sips plug-in.
Using it with the PHP Preview and Metadata Server plug-in
When both the ImageMagick Preview and the PHP Preview and Metadata Server plug-ins are enabled, ImageMagick will only be used to create previews in the following image formats:
Preview creations of JPG, GIF, and PNG files is then controlled by the PHP Preview and Metadata plug-in—a much faster working setup.