I would like to understand a bit better how thumbs are generated by
MediaWiki with the help of ImageMagick. Basically what I want to achieve
is that only 4 thumbs are generated per uploaded file.
I figured that "$wgThumbLimits"  is the setting to control this so I set:
$wgThumbLimits = array( 180, 200, 250, 300 );
I assumed that if the user can only select one of the given sizes I
would MediaWiki would only generate thumbs in the sizes defined with the
setting. What I however got is thumbs in up to 12 sizes ranging from
120px to 2880px depending on the size of the file uploaded. So this
setting is not the one and I did not really find a setting allowing me
to control thumb generation. I am kinda lost in thumbs now so any hint
will be appreciated ...