1) Use a regular <input type="file"> input.
2) On iOS, when you click the button produced by that input, one of the options is to take a photo.
3) Although I'm unaware of a way to directly populate a container field this way, in FM12 you can script it, using InsertFromURL
4) To do that, pass the path to the uploaded file as a parameter to the script.
5) Since I'm now storing the file in FM, I don't like to clutter up my webserver, after I have run the script I use php's "unlink()" function to delete the uploaded file.