The first step is to import a photo into Adobe Illustrator Draw and make a contour line drawing over it. Learn more about contour line drawings from our Fugleflick: Drawing from Experience. Then make the photo invisible and save the line drawing to the camera roll.
Crazy Photo Booth is an ancient and very basic app. I love how easy it is to use. Sometimes less choices is the BEST thing possible for productivity in the art room when you're trying to lead your students through a bunch of steps during an appsmash. Chose the contour line drawing from your camera roll, select the negative button, then save. The negative image reverses your line drawing. One of the things I love about using Adobe Draw are the smooth and forgiving lines the app creates since it is a vector tool.