Automatic resized image?

Hi,
in my portal there are several authors, and they often upload no resized images.
Can you show me how to crop images to a standard size (for ex. 300x200)?

(I tried imagesized plugin, but it doesn't work with carousel)

M site: www.pistoiasport.com

Thanks,
G.

Here is some code example if that is of any good to you:

webcheatsheet.com/php/create_thumbnail_images.php