Translations:Manual:LocalSettings.php/72/en

If you want to be able to resize images on the fly to support thumbnails, MediaWiki needs a working ImageMagick installation. Set the $UseImageResize and $UseImageMagick variables to true once you have installed and tested ImageMagick on your system. Make sure the $ImageMagickConvertCommand variable points to the proper location of the  command of your installation, that the command is executable by the web server process, and $MaxShellMemory is large enough. See Manual:Image Administration for detailed information and trouble-shooting.