Create a simulation for Watch Category website to let customers try on their hands

We want to create a website that can let customers imagine the watch they want to try on their hands with simple inputs.. - customer will input data of his wrist size in centimeter and the watch case diameter in centimeter - then the program will convert the data into one picture showing how would it look on a picture like in the attachment (1) We sell watches in our website and we want to add this feature but on another website that it will be an option to redirect the customer to that website and take the watch diameter automatically and customer will just add his arm wrist size data then do the conversion. We need to discuss on chat about anything about developing it in many things like how the watch photo can resize and cut automatically and what can be done and what is no way to be done also we may need to see a quick sample