Customize size of pictures

I realize this subject has been covered before, but I read through a lot of B-solutions and I would at some point find a GOOD solution.

Case: You upload an image and can select if it will be visible in either small-medium or big format.
In the meantime WP is filling up my folder with useless formats I will never use, but will eventually fill my image space.

Want: When I upload a HQ image I want to be able to set my width values as I see fit, and that the height is adjusting accordingly respecting the aspect ratio. Or if this is too difficult, custom my size as I see fit with a width and height value.

Wheter it is a plugin or a rewrite of the .js , please let me know.