1. Stick „arms“ of eyeglasses through a gridpaper or white paper  ( grid paper for you to print ). Place the eyeglasses in a way so you can make a front view foto. (If you don’t have a camera, you can take the picture with a flatbed scanner as well). 
   
   
2. Produce a sharp, bright front view foto, without a flash, just in normal mode – not using a wide-angle lens (like 28mm. use 50mm instead) (not activating “close” mode / flower symbol / macro mode, because that distorts the picture):
   
   

The resulting foto should look similar to this:




For best results save the foto in a high-resolution graphics-file-format, like .bmp or .png. using a resolution of 600 dpi.