I want to create a web application where user can upload their own images and they will be hosted on Amazon S3... but the problem is that I will need them resized (and croped) in various sizes (that can be eventually changed when design of the site is changed?).
What is the right way to do it... upload file to S3 and then create all the resized versions (like WordPress)?
Or may be create template tag which specifies needed size and create the images dynamically and also host them on S3. Will it be too slow because for every image I will need to check doest it exist and eventually create it?