Previous to 3.5, image manipulation in WordPress was an alchemy of mixing GD functions and WordPress functions together to turn out the desired result. GD is now abstracted out, and a new class, WP_Image_Editor, allows easy manipulation of image files. This lets you perform simple resizing, crops, flips, rotates, and real-time streaming of those results using Imagick or GD. But, that’s not all! You can also easily extend WordPress’ classes to add your own functions, or replace the entire engine with your own.
Presented at WordCamp Europe 2013 by Mike Schroder and Marko Heijnen