I needed to use ImageMagick as my thumb driver because I wanted to create GIF thumbnails automatically and GDlib doesn’t support that.
Then I found out my web hosting provider doesn’t support executing shell commands from user scripts, probably for security reasons, but unfortunately that’s exactly how Kirby uses ImageMagick.
However, the hosting provider does support calls to the Imagick API so I rewrote the commands to the API calls.
Feel free to use this code (just place the script in your site/plugins folder and enable it in config.php).
Maybe this will help someone in a similar situation