[Mediawiki-api] Images in opensearch results

As an example: The following query: http://en.wikipedia.org/w/api.php?action=opensearch&search=Berlin&f… returns 10 results, one of them: <Item> <Text xml:space="preserve">Berlin S-Bahn</Text> <Description xml:space="preserve">The Berlin S-Bahn is a rapid transit system operated by S-Bahn Berlin GmbH, a subsidiary of the Deutsche Bahn. </Description> <Url xml:space="preserve">http://en.wikipedia.org/wiki/Berlin_S-Bah… <Image source="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/S-Bah… width="50" height="50" /> </Item> has the aforementioned image tag. I think so as well. I can confirm though that it is not always returning the first image on a page. Furthermore there are some pages with images, that do not return image tags in the corresponding opensearch result. I would be interested in taking a look at the code that is generating the image tags in the opensearch results, but I have absolutly no idea where I should search for the code. Best Mad_Chom