Using Guided Access or something else for papee tracing on the screen

We are taking some water color classes. One of the techiques used is to trace printed pictures on to a canvas to create an outline to paint with. Works great when you have access to a printer. But on vacation that may not be the case. I would love to take a picture of something that I would like to paint, transfer it to my ipad, use trace paper on the screen, and then take the trace paper on to a carbon trace paper to the canvas. on the screen, as it is, the image moves around if I am not careful. There is Guided Access which does freeze the picture but puts a grey haze over the picture making it more difficult to see through tracing paper.

So is there a way to get rid of the gray area in Guided Access and still have that area insensitive to touch. Or is there an app that can freeze a photo that is insensitive to being touched?