image print option modification

We have option in ocommerce web shop where users can pick from pre-uploaded images or upload their own to print it on wallpaper or blinds. we posted this project already on another freelancer website as well but somehow the programmers not understand the meaning of the crop. What we got now is this: user can give in width and height of the wall (or blind) when done the price is calculated automatically per m2 (this is in ) the crop however is just cropping a part of the existing image, while we want to print all or most of the image of course( and thats the hard part for some programmer) My client gave me as example, give in 10 cm x 10 cm, the crop moved to that size, but i can than only print 10 cm of that picture, and thats not what i want, i want the total be scaled to the given width and height. I need a skilled programmer who can help me accomplish this. its just 1 file, but its talking too much time to get this done, and client is getting more irritated because of that. If you understand the job, it its probably less than 3 hours work. Please help me out