For those searching for more complete solutions for WordPress 2.9 etc, I have fixed incompatibilities. Here is the text from another post in a different thread here:
I have finally found the time to fix some annoying bugs when using PiwigoPress on WordPress 3.9 (and above). In addition, I have added some features I wanted to have. Here are my changes:
* fix for Piwigo 1.6 version (from the forum here)
"generate and insert" was broken and only inserted the first image
The other problem is that the URL for the PiwigoServer cannot be specified *without* a protocol and server, in case the piwigo server is on the same host. Now in my case I have the blog in <server>/blog and the piwigo in <server>/piwigo, and I would like PiwigoPress to use "/piwigo" as url and have the proper (currently used) http/https added automatically.
Both of these things have been fixed in the code, that means, that one can now have the full communication encrypted.
The patch is available at http://www.preining.info/software/piwigopress.diff
The changes I made are also available via the gitorious project wp-piwigo, see here: https://gitorious.org/wp-piwigo/wp-piwigo/
I would happily contribute this to the subversion and upstream.