I'm not good at English either.... and whatever...
If you are not gonna do it by writing your own application. There's no way you can do that!!!
First, taking photos frequently as you described needs private apis. That will make your app rejected from App Store. If that's okay, read the instructions below.
Dump headers of a Private Library called 'PhotoLibrary'.
Setup your project in XCode.
Add [[PLCameraController sharedInstance] previewView] to your UIWindow, in applicationDidFinishLaunching:.
Create a NSTimer, repeats every (30/20) secs.
In the timer's callback, run
UIImage *image = [[PLCameraController sharedInstance] _createPreviewImage];
Then you will get a UIImage every 1.5 second. Do whatever you need to do. You might need to save them to Photo Album by calling UIImageWriteToAlbum().
Notice:
This will only take photos of a low resolution. It's impossible to take full resolution photo per 1.5 second.
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