Hi, I'm the author of the imgSeek (http://server.imgseek.net/) open-source database server. This software is capable of adding content-based (visual) image searching to any image related website or software.

Have you considered adding content-based (visual) image searching features to ZenPhoto? This could be done either by embedding imgSeek code into ZenPhoto or connecting to the imgSeek server via XML-RPC/SOAP.

Please let me know your thoughts.

No, we have not as our built in search engine is not only for images but Zenpage articles and pages as well. (I admit I have never heard of your tool at all... I know Google has a similar function).

But we welcome any third party tools in form of plugins.

Adobe has something similar, yet seems to be much more powerfull.

http://tv.adobe.com/watch/max-2011-sneak-peeks/max-2011-sneak-peek-pixel-nuggets/