Position template image instead of offset calculation

If you use a template image, it uses the format of the template image and not the actual format to be printed. For example A3 format. Using offset you need to calculate the actual size. That's pretty hard.

It would be a great addition if the template image is based on the print format. For a shirt with an A3 print, the canvas must be 297x420. The template image can be positioned independently of the print format.