使用 AVFoundation 在 Iphone 照片捕获中图像捕获比闪存慢答案

【问题标题】：Image capture is slower than flash in Iphone photo capture using AVFoundation使用 AVFoundation 在 Iphone 照片捕获中图像捕获比闪存慢
【发布时间】：2018-07-31 07:02:51
【问题描述】：

我们正在使用最新的 Swift 代码和 AVFoundation API 来创建一个相机应用程序，它具有 Flash、反向相机和捕捉照片功能。代码需要支持 ios10 以上。

我们遇到的问题是相机闪光灯出现，但没有在照片中被捕捉（基本上相机闪光灯出现的时间比照片捕捉快一点，或者照片捕捉比闪光灯慢一点）这使得我们的闪光灯功能无用.

这里是我们相机捕捉的代码：

//Function to capture the image from the camera session -> this gets called from the ViewController Outlet action OnCapture
func capture() throws {
    guard captureSession.isRunning else {
        throw CameraRuntimeError.captureSessionIsMissing
    }
    let settings = AVCapturePhotoSettings()
    if getCurrentCamera().isFlashAvailable {
        settings.flashMode = self.flashMode
    }
    self.photoOutput?.capturePhoto(with: settings, delegate: self)
}

这是代表：

extension CameraFunctions: AVCapturePhotoCaptureDelegate {
private static let failedToConvertToJPEGErrorCode = "JPEGERROR"
private static let failedToCaptureImage = "CAMERROR"
public func photoOutput(_ captureOutput: AVCapturePhotoOutput,
                        didFinishProcessingPhoto photoSampleBuffer: CMSampleBuffer?,
                        previewPhoto previewPhotoSampleBuffer: CMSampleBuffer?,
                        resolvedSettings: AVCaptureResolvedPhotoSettings,
                        bracketSettings: AVCaptureBracketedStillImageSettings?, error: Swift.Error?) {
    if error != nil {
        onPhotoCaptured(StringResult(error: ServicesError(CameraFunctions.failedToCaptureImage, error!.localizedDescription)))
    }
    if let buffer = photoSampleBuffer, let data = AVCapturePhotoOutput.jpegPhotoDataRepresentation(forJPEGSampleBuffer: buffer, previewPhotoSampleBuffer: nil) {
        let encodedString = //DO ENCODING OF THE PHOTO
        onPhotoCaptured(encodedString)
    } else {
        onPhotoCaptured(StringResult(error: ServicesError(CameraFunctions.failedToConvertToJPEGErrorCode, CameraRuntimeError.failedToConvertImageToJPEG.localizedDescription)))
    }
        closeCaptureSession()
    }
}

onPhotoCaptured 存在于 ViewController 中。

如果我们做错了什么，请告诉我们。

【问题讨论】：

标签： iphone swift camera avfoundation ios11

【解决方案1】：

为照片输出设置准备好的设置解决了这个问题：

func capture(_ delegate: AVCapturePhotoCaptureDelegate, _ onError: @escaping (Error) -> Void) throws {
    guard captureSession.isRunning else {
        throw CameraRuntimeError.captureSessionIsMissing
    }
    let settings: AVCapturePhotoSettings
    if #available(iOS 11.0, *) {
        settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])
        settings.isAutoStillImageStabilizationEnabled = true
    } else {
        settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecJPEG])
    }
    if getCurrentCamera().isFlashAvailable {
        settings.flashMode = self.flashMode
    }

    //This statement did the magic
    self.photoOutput?.setPreparedPhotoSettingsArray([settings]) { (suc: Bool, err: Error?) -> Void in
        if suc {
            self.photoOutput?.capturePhoto(with: settings, delegate: delegate)
        }
        if err != nil {
            onError(err!)
        }
    }
}

【讨论】：