ext-gd * -> the requested PHP extension gd is missing from your system. code example
Example: gumlet/php-image-resize 1.9.2 requires ext-gd *
#php -v to get version (change to php7.2 or whatever version if needed)
sudo apt-get install php7.0-gd
#php -v to get version (change to php7.2 or whatever version if needed)
sudo apt-get install php7.0-gd