sorry to be still on this subject but here in Australia at least they still make LEAD pencils so really this is just a warning to everyone to make sure they are using GRAPHITE pencils when transferring onto cookies or food. I thought like most people that they stopped producing lead pencils but apparently not so.
Thanks for sharing the camera apps available. Need it badly.
I have a method that could work for you I take a piece of parchment paper a little bigger than the photo I place over the photo I trace it ..you could use a pencil or pen whatever preference you like, then I take a hot glue gun, I take the smallest hole attachment and start tracing the picture I traced, I let the glue dry and very carefully take the glue gun and add another layer of glue on top of the one I did before that that's dried I then let them both dry I take food colouring you can use any colour I use a sponge and I DAB it into the food colouring and rub it on top of the pattern, I then take my cookie and pressing onto the sketch or you can take the sketch and press on to the cookie this takes some trial-and-error you can keep your sketches or templates by placing a piece of parchment paper over the part you put food colouring on and store them in a box for later use you have to be careful with small detailed areas I hope this can work for you