I'm creating a website where the user can upload several images to his album, the thing is that I want to allow him to crop the image, specially because he might upload a very vertical image and we want them to be at the same size and aspect ratio.
Gravatar for instance does that way:
I want to allow the user to select an image, crop and then continue selecting images, like this:
And when he is done he will press upload and that is it.
How can I accomplish something like this?