iOS 10 的 Photography

iOS 10中新特性：

• 有史以来第一次，你的app 可以拍摄和编辑 live photos
• 可以响应不同的图片捕获

一、相机捕获内容显示（输入）

1. 创建名为PhotoMe并设置只有IPhone使用的项目，竖屏。
2. 授权：在Info.plist 中添加

<key>NSCameraUsageDescription</key>
    <string>PhotoMe needs the camera to take photos. Duh!</string>
    <key>NSMicrophoneUsageDescription</key>
    <string>PhotoMe needs the microphone to record audio with Live Photos.</string>
    <key>NSPhotoLibraryUsageDescription</key>
    <string>PhotoMe will save photos in the Photo Library.</string>

3. 自定义View：创建名为CameraPreviewView 的UIView子类

import UIKit
import AVFoundation
import Photos
class CameraPreviewView: UIView {
    //1
    override class var layerClass: AnyClass {
        return AVCaptureVideoPreviewLayer.self
    }
    //2
    var cameraPreviewLayer: AVCaptureVideoPreviewLayer {
        return layer as! AVCaptureVideoPreviewLayer
    }
    //3
    var session: AVCaptureSession? {
        get {
            return cameraPreviewLayer.session
        }
        set {
            cameraPreviewLayer.session = newValue
        }
    } 
}

4. 画界面：在Main.storyboard 中，拖入一个UIView，并设定约束，上，左，右和父视图对齐，宽高比为3:4，设置自定义类为CameraPreviewView，向ViewController连接名为cameraPreviewView的outlet属性。
5. 在ViewController中：

import AVFoundation

添加属性：

    fileprivate let session = AVCaptureSession()
    fileprivate let sessionQueue = DispatchQueue(label: "com.razeware.PhotoMe.session-queue")
    var videoDeviceInput: AVCaptureDeviceInput!

添加方法：

    private func prepareCaptureSession() {
        // 1
        session.beginConfiguration()
        session.sessionPreset = AVCaptureSessionPresetPhoto
        
        do {
            // 2
            let videoDevice = AVCaptureDevice.defaultDevice(
                withDeviceType: .builtInWideAngleCamera,
                mediaType: AVMediaTypeVideo,
                position: .front)
            // 3
            let videoDeviceInput = try
                AVCaptureDeviceInput(device: videoDevice)
            
            // 4
            if session.canAddInput(videoDeviceInput) {
                session.addInput(videoDeviceInput)
                self.videoDeviceInput = videoDeviceInput
                
                // 5
                DispatchQueue.main.async {
                    self.cameraPreviewView.cameraPreviewLayer
                        .connection.videoOrientation = .portrait
                }
            } else {
                print("Couldn't add device to the session")
                return
            }
        } catch {
            print("Couldn't create video device input: \(error)")
            return
        }
        
        // 6
        session.commitConfiguration()
    }

在viewDidLoad() 中,授权，配置session：

        //1
        cameraPreviewView.session = session
        //2
        sessionQueue.suspend()
        //3
        AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo) {
            success in
            if !success {
                print("Come on, it's a camera app!")
                return
            }
            //4
            self.sessionQueue.resume()
        }
        
        sessionQueue.async {
            [unowned self] in
            self.prepareCaptureSession()
        }

在viewWillAppear() 中,启动session：

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        sessionQueue.async {
            self.session.startRunning()
        }
    }

二、拍照（输出）

1. 在ViewController 中：
   添加属性：

fileprivate let photoOutput = AVCapturePhotoOutput()

prepareCaptureSession()中，prepareCaptureSession()前面：

 if session.canAddOutput(photoOutput) {
     session.addOutput(photoOutput)
     // 必须在session启动之前配置，否则会发生闪烁
     photoOutput.isHighResolutionCaptureEnabled = true
 } else {
     print("Unable to add photo output")
     return
 }

2. 画界面：
3. 在Main.storyboard 中设置main view 和 camera preview view 的background 为black，main view的tint color 为 orange。
4. main view拖入Visual Effect View With Blur,设置约束为左，下，右与父视图对齐。 Blur Style 为 Dark。
5. Visual Effect View With Blur 拖入 button，名称为Take Photo!,字体为20，并将其放入stack View 中。
6. 对stack View 添加顶部距父视图为5，底部距父视图为20的约束。
7. 连接button到ViewController 中：

@IBOutlet weak var shutterButton: UIButton!
@IBAction func handleShutterButtonTap(_ sender: UIButton) {
        capturePhoto()
}

extension ViewController {
    fileprivate func capturePhoto() {
        // 1
        let cameraPreviewLayerOrientation = cameraPreviewView
            .cameraPreviewLayer.connection.videoOrientation
        
        // 2
        sessionQueue.async {
            if let connection = self.photoOutput
                .connection(withMediaType: AVMediaTypeVideo) {
                connection.videoOrientation =
                cameraPreviewLayerOrientation
            }
            
            // 3
            let photoSettings = AVCapturePhotoSettings()
            photoSettings.flashMode = .off
            photoSettings.isHighResolutionPhotoEnabled = true
            
        }
    }
}

4. 创建代理：因为一张照片还没处理完就可以拍另一张，所以ViewController 持有一个键为AVCapturePhotoSettings，值为代理的字典。

import AVFoundation
import Photos
class PhotoCaptureDelegate: NSObject {
    // 1
    var photoCaptureBegins: (() -> ())? = .none
    var photoCaptured: (() -> ())? = .none
    fileprivate let completionHandler: (PhotoCaptureDelegate, PHAsset?)-> ()
    
    // 2
    fileprivate var photoData: Data? = .none
    
    // 3
    init(completionHandler: @escaping (PhotoCaptureDelegate, PHAsset?) -> ()) {
        self.completionHandler = completionHandler
    }
    
    // 4
    fileprivate func cleanup(asset: PHAsset? = .none) {
        completionHandler(self, asset)
    }
}

5. 原理如图：

   
   photo capture.png
6. 实现代理方法

extension PhotoCaptureDelegate: AVCapturePhotoCaptureDelegate {
    // Process data completed
    func capture(_ captureOutput: AVCapturePhotoOutput,
                 didFinishProcessingPhotoSampleBuffer
        photoSampleBuffer: CMSampleBuffer?,
                 previewPhotoSampleBuffer: CMSampleBuffer?,
                 resolvedSettings: AVCaptureResolvedPhotoSettings,
                 bracketSettings: AVCaptureBracketedStillImageSettings?,
                 error: Error?) {
        
        guard let photoSampleBuffer = photoSampleBuffer else {
            print("Error capturing photo \(error)")
            return
        }
        photoData = AVCapturePhotoOutput
            .jpegPhotoDataRepresentation(
                forJPEGSampleBuffer: photoSampleBuffer, previewPhotoSampleBuffer: previewPhotoSampleBuffer)
    }
    
    // Entire process completed
    func capture(_ captureOutput: AVCapturePhotoOutput,
                 didFinishCaptureForResolvedSettings
        resolvedSettings: AVCaptureResolvedPhotoSettings,
                 error: Error?) {
        
        // 1
        guard error == nil, let photoData = photoData else {
            print("Error \(error) or no data")
            cleanup()
            return
        }
        
        // 2
        PHPhotoLibrary.requestAuthorization {
            [unowned self]
            (status) in
            // 3
            guard status == .authorized else {
                print("Need authorisation to write to the photo library")
                self.cleanup()
                return
            }
            // 4
            var assetIdentifier: String?
            PHPhotoLibrary.shared().performChanges({
                let creationRequest = PHAssetCreationRequest.forAsset()
                let placeholder = creationRequest
                    .placeholderForCreatedAsset
                
                creationRequest.addResource(with: .photo,
                                            data: photoData, options: .none)
                
                assetIdentifier = placeholder?.localIdentifier
                
            }, completionHandler: { (success, error) in
                if let error = error {
                    print("Error saving to the photo library: \(error)")
                }
                var asset: PHAsset? = .none
                if let assetIdentifier = assetIdentifier {
                    asset = PHAsset.fetchAssets(
                        withLocalIdentifiers: [assetIdentifier],
                        options: .none).firstObject
                }
                self.cleanup(asset: asset)
            })
        }
    }
}

7. 在ViewController中：
   添加属性：

fileprivate var photoCaptureDelegates = [Int64 : PhotoCaptureDelegate]()

在capturePhoto（）的queue 闭包末尾添加：

            // 1
            let uniqueID = photoSettings.uniqueID
            let photoCaptureDelegate = PhotoCaptureDelegate() {
                [unowned self] (photoCaptureDelegate, asset) in
                self.sessionQueue.async { [unowned self] in
                    self.photoCaptureDelegates[uniqueID] = .none
                }
            }
            // 2
            self.photoCaptureDelegates[uniqueID] = photoCaptureDelegate
            // 3
            self.photoOutput.capturePhoto(
                with: photoSettings, delegate: photoCaptureDelegate)

三、难以置信的

1. 添加闪屏动画
   在capturePhoto（）创建delegate 后，添加：
   photoCaptureDelegate.photoCaptureBegins = { [unowned self] in
   DispatchQueue.main.async {
   self.shutterButton.isEnabled = false
   self.cameraPreviewView.cameraPreviewLayer.opacity = 0
   UIView.animate(withDuration: 0.2) {
   self.cameraPreviewView.cameraPreviewLayer.opacity = 1
   }
   }
   }
   photoCaptureDelegate.photoCaptured = { [unowned self] in
   DispatchQueue.main.async {
   self.shutterButton.isEnabled = true
   }
   }
   在PhotoCaptureDelegate的extension 中：

    func capture(_ captureOutput: AVCapturePhotoOutput,
                 willCapturePhotoForResolvedSettings
        resolvedSettings: AVCaptureResolvedPhotoSettings) {
        photoCaptureBegins?()
    }
    func capture(_ captureOutput: AVCapturePhotoOutput,
                 didCapturePhotoForResolvedSettings
        resolvedSettings: AVCaptureResolvedPhotoSettings) {
        photoCaptured?()
    }

2. 展示缩略图

• 获取缩略图：在PhotoCaptureDelegate添加属性：

var thumbnailCaptured: ((UIImage?) -> ())? = .none

在代理方法didFinishProcessingPhotoSampleBuffer末尾添加:

        if let thumbnailCaptured = thumbnailCaptured,
            let previewPhotoSampleBuffer = previewPhotoSampleBuffer,
            let cvImageBuffer =
            CMSampleBufferGetImageBuffer(previewPhotoSampleBuffer) {
            
            let ciThumbnail = CIImage(cvImageBuffer: cvImageBuffer)
            let context = CIContext(options: [kCIContextUseSoftwareRenderer:
                false])
            let thumbnail = UIImage(cgImage: context.createCGImage(ciThumbnail,
                                                                   from: ciThumbnail.extent)!, scale: 2.0, orientation: .right)
            
            thumbnailCaptured(thumbnail)
        }

• 画界面：设置switch 为 off，label 的文本颜色为white，imageView 的 clip to bounds 为 true，content mode 为 Aspect Fill。

  
  main storyboard.png
  UI.png
  

  连线：

    @IBOutlet weak var previewImageView: UIImageView!
    @IBOutlet weak var thumbnailSwitch: UISwitch!

• 设置缩略图格式： 在capturePhoto（）中，创建delegate之前添加：

            if self.thumbnailSwitch.isOn
                && photoSettings.availablePreviewPhotoPixelFormatTypes
                    .count > 0 {
                photoSettings.previewPhotoFormat = [
                    kCVPixelBufferPixelFormatTypeKey as String :
                        photoSettings
                            .availablePreviewPhotoPixelFormatTypes.first!,
                    kCVPixelBufferWidthKey as String : 160,
                    kCVPixelBufferHeightKey as String : 160
                ]
            }

• 展示缩略图：在创建delegate之后添加：

            photoCaptureDelegate.thumbnailCaptured = { [unowned self] image in
                DispatchQueue.main.async {
                    self.previewImageView.image = image
                }
            }

3. Live Photos

• 画界面：在Option Stack 中拖入一Horizontal Stack View，嵌入一个switch 和 一个 label，设置switch 为 off，label 的text 为 Live Photo Mode, text color 为 white。向Control Stack 加入一个label ，text 为 capturing...，字体大小为35，hidden 为 true，text color 为 orange。
  连线：

    @IBOutlet weak var capturingLabel: UILabel!
    @IBOutlet weak var livePhotoSwitch: UISwitch!

• 添加音频输入：在prepareCaptureSession()中，创建video device input 之后添加：

        do {
            let audioDevice = AVCaptureDevice.defaultDevice(withMediaType:
                AVMediaTypeAudio)
            let audioDeviceInput = try AVCaptureDeviceInput(device: audioDevice)
            if session.canAddInput(audioDeviceInput) {
                session.addInput(audioDeviceInput)
            } else {
                print("Couldn't add audio device to the session")
                return
            }
        } catch {
            print("Unable to create audio device input: \(error)")
            return
        }

• 设置Photo 输出：在photoOutput.isHighResolutionCaptureEnabled = true 之后添加：

            photoOutput.isLivePhotoCaptureEnabled =
                photoOutput.isLivePhotoCaptureSupported
            DispatchQueue.main.async {
                self.livePhotoSwitch.isEnabled =
                    self.photoOutput.isLivePhotoCaptureSupported

• 设置输出路径：在capturePhoto（）中，创建delegate之前添加：
  if self.livePhotoSwitch.isOn {
  let movieFileName = UUID().uuidString
  let moviePath = (NSTemporaryDirectory() as NSString)
  .appendingPathComponent("(movieFileName).mov")
  photoSettings.livePhotoMovieFileURL = URL(
  fileURLWithPath: moviePath)
  }
• 捕获live photo：在PhotoCaptureDelegate添加属性：

    var capturingLivePhoto: ((Bool) -> ())? = .none
    fileprivate var livePhotoMovieURL: URL? = .none

在代理方法willCapturePhotoForResolvedSettings末尾添加:

        if resolvedSettings.livePhotoMovieDimensions.width > 0
            && resolvedSettings.livePhotoMovieDimensions.height > 0 {
            capturingLivePhoto?(true)
        }

添加代理方法：

    func capture(_ captureOutput: AVCapturePhotoOutput,
                 didFinishRecordingLivePhotoMovieForEventualFileAt
        outputFileURL: URL,
                 resolvedSettings: AVCaptureResolvedPhotoSettings) {
        capturingLivePhoto?(false)
    }
    
    func capture(_ captureOutput: AVCapturePhotoOutput,
                 didFinishProcessingLivePhotoToMovieFileAt outputFileURL:
        URL,
                 duration: CMTime,
                 photoDisplay photoDisplayTime: CMTime,
                 resolvedSettings: AVCaptureResolvedPhotoSettings,
                 error: Error?) {
        if let error = error {
            print("Error creating live photo video: \(error)")
            return
        }
        livePhotoMovieURL = outputFileURL
    }

• 添加视频到相册：在代理方法didFinishCaptureForResolvedSettings:error:)中，addResource 后添加:

                
                if let livePhotoMovieURL = self.livePhotoMovieURL {
                    let movieResourceOptions = PHAssetResourceCreationOptions()
                    movieResourceOptions.shouldMoveFile = true
                    creationRequest.addResource(with: .pairedVideo,
                                                fileURL: livePhotoMovieURL, options:
                        movieResourceOptions)
                }

• 更新UI：在ViewController添加属性：

fileprivate var currentLivePhotoCaptures: Int = 0

在capturePhoto()中，创建delegate之后添加：

            // Live photo UI updates
            photoCaptureDelegate.capturingLivePhoto = { (currentlyCapturing) in
                DispatchQueue.main.async { [unowned self] in
                    self.currentLivePhotoCaptures += currentlyCapturing ? 1 : -1
                    UIView.animate(withDuration: 0.2) {
                        self.capturingLabel.isHidden =
                            self.currentLivePhotoCaptures == 0
                    }
                }
            }