Ubuntu and Debian issues

Install

GD library

sudo apt-get install php5-gd
sudo /etc/init.d/apache2 restart

jpegtran / pngcrush support

sudo apt-get install libjpeg-progs
sudo apt-get install pngcrush

Support

Some functions are only available if PHP is compiled with the bundled version of the GD library.

ImageUtil tries to solve these issues by using custom functions where possible, but because they are written in PHP, they are much slower than the bundled versions.