Manual:$wgCustomConvertCommand

Details
To use another resizing converter, e.g. GraphicMagick, set this variable to the command-line string required to launch the executable. If no string is specified, then MediaWiki's internal resizing code will be used.

In the command-line string, the following variables will be expanded:


 * will be replaced with the source path


 * will be replaced with the destination


 * will be replaced with the width


 * will be replaced with the height

Examples
This is the command you would set for GraphicMagick:

This is the command you would set for using ImageMagick to overlay your files in tiles with e.g. a watermark file:

Bitmaps vs. SVG
is only used for Bitmaps. If you're looking for an alternative to ImageMagick to convert your SVG files, you need to use.