1.通过UIImagePickerController的方式进行拍摄。
2.通过 AV Foundation framework 提供的接口进行拍摄。
https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/CameraAndPhotoLib_TopicsForIOS/Introduction/Introduction.html#//apple_ref/doc/uid/TP40010405-SW1
Taking Pictures and Movies
截图 怎样使用UIImagePickerController 方法拍照
https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/CameraAndPhotoLib_TopicsForIOS/Articles/TakingPicturesAndMovies.html#//apple_ref/doc/uid/TP40010406-SW1
UIKit Framework Reference 全部UIKit Framework的接口文档
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIKit_Framework/index.html#classes
UIImagePickerController的具体接口内容 Available in iOS 2.0 and later.
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIImagePickerController_Class/index.html
About AV Foundation 介绍AV Foundation的架构 （AV Foundation Programming Guide）
https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html#//apple_ref/doc/uid/TP40010188
AV Foundation Framework Reference 全部AV Foundation的接口文档
https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVFoundationFramework/index.html#classes
Media Capture and Access to Camera
Recording input from cameras and microphones is managed by a capture session. A capture session coordinates the flow of data from input devices to outputs such as a movie file. You can configure multiple inputs and outputs for a single session, even when the
session is running. You send messages to the session to start and stop data flow.
In addition, you can use an instance of a preview layer to show the user what a camera is recording.
具体介绍 av foundation 怎样拍照
截图
https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/04_MediaCapture.html#//apple_ref/doc/uid/TP40010188-CH5-SW2
其它：
AV Foundation is available in iOS 4.0 and later, and OS X 10.7 and later
IOS8 新增功能点：
https://developer.apple.com/library/ios/releasenotes/General/WhatsNewIniOS/Articles/iOS8.html#//apple_ref/doc/uid/TP40014205-SW1
Manual Camera Controls：
The AV Foundation framework (AVFoundation.framework) makes it easier than ever to take great photos. Your app can take direct control over the camera focus, white balance, and exposure settings. In addition, your app can use bracketed exposure captures to automatically
capture images with different exposure settings.
Improved Camera Functionality
Use the following APIs to discover and enable new camera features found on the iPhone 6 and iPhone 6 Plus:
A new property (videoHDRSupported) can determine whether a capture device supports high dynamic range streaming.
A new video stabilization mode (AVCaptureVideoStabilizationModeCinematic) provides more cinematic results in the captured video.
A new property (highResolutionStillImageOutputEnabled) can be used to set an AVCaptureStillImageOutput object to capture still pictures at a higher resolution.
A new property (autoFocusSystem) can be used to determine how the camera performs auto focusing.
IOS8的代码变化。
当中重点关注avfoundation的几个class变化。
https://developer.apple.com/library/ios/releasenotes/General/iOS80APIDiffs/frameworks/AVFoundation.html
What's New in iOS 每一个IOS版本号的公布内容变化
https://developer.apple.com/library/ios/releasenotes/General/WhatsNewIniOS/Introduction/Introduction.html#//apple_ref/doc/uid/TP40008244-SW1