This is also an important means to slim down the iPhone: since these files cannot be deleted from the iPhone's photo app by themselves, the garbage cleaning function of tools such as synchronization assistants will not be cleaned (because they are not garbage). But over time, it will become very big, and it may reach one or two G's. If you delete all the photos in the "camera roll" and find that your photo app still takes up a lot of space (you can find it in "Settings-General-Use"), then there is no doubt that they are occupied.
If you don't mind the picture being compressed, you can copy it from photo stream. Photo stream pictures have two characteristics: ① compressed to about half the size of the original picture; ② Preserve the filter effect. Photo stream's picture address is: /PhotoStreamsData. Find a folder full of numbers under this folder. After entering, folders such as 100APPLE, 10 1APPLE will appear. This is your photo of photo stream.