Working with images in PHP can be tricky but sFire has a built-in image driver which gives you the tools to easily resize, crop, extract (base) colors and more.
There is one image driver you can use for manipulating images.
sFire\Image\Driver\GD image is based on the popular PHP GD library.
use sFire\Image\Image;
$image = new Image('GD');
Click here to view more information about the usage of the GD image driver.