Slow Publishing in Movable Type caused by ImageValidate plugin

This blog runs on the Movable Type engine, selected mainly because I like the fact that it publishes a static HTML file for each article.

For a long time, Movable Type appeared to be slowing down at publishing posts, particularly ones containing many images. It could take anywhere from a few seconds to five minutes or more just to publish an article! Yet when the images were not uploaded as Movable Type “assets” but simply added using HTML image tags, the publishing went much faster.

The source of the problem turned out to be a plugin called “ImageValidate”, an old plugin that I don’t even remember adding to the system. According to its read-me file,

“ImageValidate is meant to help authorized Movable Type administrators identify images that contain harmful HTML and prevent those file from being uploaded into the Movable Type Asset Manager.

If an image file containing HTML is uploaded, the plugin will cause the following error to be displayed: “Saving [filename] failed: Invalid image file format.”