ImageMagick is a very popular image editing suite, and for good reasons. It's command-based and is very capable: making it perfect as a backend to many other image manipulation tools.

The default image library for PHP is GD. You can use ImageMagick to replace GD in PHP by installing php-imagick on Ubuntu following these steps;

1. Update apt's package list.

   $ sudo apt update

2. Install php-imagick package.

   $ sudo apt install -y php-imagick

3. Check if imagick module is loaded by PHP.

   $ php -m | grep imagick
   imagick

4. Restart Apache or any other services dependent on PHP.

   $ sudo systemctl restart apache2