class.upload.php is a powerful and mature PHP class to manage uploaded files, and manipulate images in many ways. The script is available under a GPL license.
more info about the class
$handle->image_resize = true; $handle->image_ratio = true; $handle->image_x = 500; $handle->image_y = 500;
I've this config:
So, when it tries to resize to 500 image_y, x can't be resized. And it doesn't work.
;-)