@sgspecker This allows to create a new photo with updated caption in camera roll if you share an existing photo which has already a caption

import appex import console import os import photos def main(): if appex.is_running_extension(): fil = appex.get_attachments()[0] else: fil = 'a.jpg' with open(fil, mode='rb') as fin: b = fin.read() #b'\xff\xed\xllllPhotoshop 3.0\x00' = marker APP1 # ----- #b'8BIM\x04\x04\x00\x00\x00\x00\x00\x17\x1c\x01Z\x00\x03\x1b%G\x1c\x02\x0\x0\x02 # --- #b'\x00\x02\x1c\x02x\x00\x03Cap\x00 ip = b.find(b'Photoshop') if ip >= 0: #print(b[ip-6:ip+100]) lip = int.from_bytes(b[ip-2:ip], "big") i8 = b.find(b'8BIM',ip) if i8 >= 0: l8 = int.from_bytes(b[i8+10:i8+12], "big") i = b.find(b'\x1c\x02x', i8) # caption field identified by x'1c0278' then length in 2 bytes x'0005' = 5 l = int.from_bytes(b[i+3:i+5], "big") caption = b[i+5:i+5+l].decode("utf-8") #print(caption) #return # if no update # caption = console.input_alert('new caption?','', caption, 'ok', hide_cancel_button=True) lu = len(caption) bl = lu.to_bytes(2,'big') # x'000l' # store new caption b = b[:i+3] + bl + caption.encode('utf-8') + b[i+5+l:] # change length of 8BIM marker l8aft = l8 - l + lu bl8aft = l8aft.to_bytes(2,'big') # x'000l' b = b[:i8+10] + bl8aft + b[i8+12:] # change length of Photoshop marker at ip-2 lipaft = lip - l + lu blaft = lipaft.to_bytes(2,'big') # x'000l' b = b[:ip-2] + blaft + b[ip:] tmp = '_temp.jpg' with open(tmp, mode='wb') as fout: fout.write(b) asset = photos.create_image_asset(tmp) os.remove(tmp) appex.finish() if __name__ == '__main__': main()