WordPress has come a very long way (especially since v3) in terms of its image or media management system, making it extremely easy for you to add custom image sizes, featured images, cropping etc.
Theme developers are now spoilt for choice when it comes to adding image management capabilities to their themes, and users have more control than ever before on how they add and manipulate the images they upload.
These improvements however, bring a level of complexity that can only be understood through hours of research and practice to get the perfect balance in terms of how images are added and manipulated from an extension or theming perspective.
Fortunately, Ade, over at www.studiograsshopper.ch has come to the rescue and done all the hard graft for you already.
Ade has meticulously studied and documented every aspect of how wordpress’s media system works and how best you can approach its implementation.
We were amazed at the level of detail Ade went into in order to make this topic extremely clear for everyone and are sure you will be as well: “WordPress Featured Images – add_image_size() resizing and cropping demo“