Smart Image Resizer allows us to resize and crop any image on our websites without touching the actual image or writing any code. We upload each image (JPEGs, GIFs, and PNGs) once at a high enough resolution and can then reuse it at any size we want, anywhere we want. It doesn’t matter if the images are in a post, on a page, or in a template file, it just works. All of the magic is done through the query string part of the URL in the src attribute of the img tag.
Requirements: PHP and GD
License: Creative Commons 3.0 License