android - Share a photograph to a website from the "share with" button -

i working on school project , there don't know how to.

first, let me explain project.

this system, composed of raspberry, can connect rasp wi-fi , go website typing specefic ip in url bar of native browser of phone, once on website, can upload photograph on raspberry, connected projector, , make slide of pictures uploaded peoples.

the problem annoying use browser, type ip , click on button upload photo, want can upload picture our site going on native gallery app of phone, choose picture , click on "share with" choose option upload picture our site. don't know if possible if have idea of how can it, nice tell us. have know can't make app phone , nice if can works on ios, android , windows phone.

i searched "sharing picture on phone wi-fi" found nothing.