For $5.00 you can make a Lucida camera drawing aid. Check out the demo. You are able to take one of your patterns and scan it or a picture into your I-pad and create a new pattern with little effort. I need to get an I-pad now. the demo really looks like it would really help out us marginal artist. You can even take a photo of 3 D pieces with the I-Pad and create line drawings from it.
This you tube will help you understand how it works.
Here is the web site. https://itunes.apple.com/app/camera-lucida/id362499096?mt=8
and a demo. http://www.cameralucidaapp.com/tutorials.html
The picture below is looking at a I-Phone screen the face is the photo and the pen is on your drawing service.