When dia file is included into documentation, it is referenced using full path instead of simple ./image.png. This makes it very hard to publish documentation on the web, because absolute filesystem path is completely different than final URI.

Since images and HTML files are put into single flat directory, simply ommit any path from the img tag and it will be all fine.

If some subdirs are used, use ../../ (or as many of them is required to get back to base dir) as prefix and then append full path within html dir. This way there may be some redundant ../, but output generator will be simple to implement.