this is because, instead of images/media being decoded and encoded per operation, only on the last `photu write` call, until then it is only creating a JSON pla

this is because, instead of images/media being decoded and encoded per operation, only on the last `photu write` call, until then it is only creating a JSON plan, which is also checked for bad args. no need to touch a pixel until you know all the operations that will be taking place!