Possible duplicate: UIImagePickerController does not show edit screen
According to takePicture: method in Apple documentation:
Use this method in conjunction with a custom overlay view to initiate the programmatic capture of a still image. This supports taking more than one picture without leaving the interface, but requires that you hide the default image picker controls.
Calling this method while an image is being captured has no effect. You must wait until the associated delegate object receives an imagePickerController:didFinishPickingMediaWithInfo: message before you can capture another picture.
It seems that this approach (custom overlay) it is configured in order to be managed by yourself. Even if "allowsEditing = YES" the taken picture will be directly sent to imagePickerController:didFinishPickingMediaWithInfo:.
Based on that if we want to edit the taken picture using our custom user interface we should create an according custom edit screen for that purpose.