It seems that Sonata Media has only two strategies when it comes to cropping/resizing the uploaded image, Sonata\MediaBundle\Resizer\SimpleResizer and Sonata\MediaBundle\Resizer\SquareResizer. Both these strategies are automatic, meaning that the users don't have a say in how they want the image to be resized/croppped.
I would like to give the user an option to select the portion of the image that is more relevant, kind like the jQuery Image Cropper library used by GenemuFormBundle, but I don't even know where to start. Will I need to create my own Admin class instead of using Sonata\MediaBundle\Admin\BaseMediaAdmin? Has anyone write a bundle that I can use? How do you manage your galleries usually?
I wrote a simple admin extension that give you the ability to customize the images by format. It's actually a Work In Progress that needs some test, documentation and refactoring, but it does the job, it's lightweight and it's shipped with a resizer to handle fixed dimensions.
You can find it here: https://github.com/julien-maitan/sonata-media-crop