[API shopping coding]

I have website with a API coded shopping shopping cart.  I need a code so when a customer uploads an image they can resize the image by clicking on the different arrows to make the image smaller or larger and center it on the garment.  I guess you can tell from the way Im asking this question that Im not a tech person and I dont know if Im in the right place to ask the question.  So any help or direction you can give will be most welcomed.