iPhone photo exposure compensation

Is there an API to control the exposure of a photo before it has been actually taken on an iPhon开发者_如何学Pythone?

---

there is no "official" way you can directly control exposure compensation. But you can get different exposure images by choosing different exposure points. There are API's to set metering points.

You can directly control compensation using undocumented API's. For more information on undocumented API's : Accessing iOS 6 new APIs for camera exposure and shutter speed

---

maybe u could give more description of the question.

if u want to change the screen content when the camera is open, the only way is UIImagePickerController which has a cameraOverlayView, u can put some overlay on the screen by it. and use the cameraViewTransform to control the camera image transform.