iOS在使用AVAssetWriter捕获视频时如何正确处理方向
iOS在使用AVAssetWriter捕获视频时如何正确处理方向
提问于 2017-03-02 11:24:18
我正在制作一个使用AVFoundation录制视频的示例应用程序。关键是我可以更好地控制视频的录制方式。在我的示例项目中，我有视频捕获，但正在努力正确地处理方向。
我在网络上做了很多搜索，发现其他人建议我不应该让捕获视图或捕获会话根据方向旋转，而是设置一个转换来在播放过程中旋转视频。我在iOS和Mac设备上做得很好，但我想知道我是否会在其他平台上遇到问题，比如Windows或安卓。
此外，当我查看录制的视频元数据时，我会看到宽度和高度没有正确地设置为定向。这是有意义的，因为我只是在改变视频的呈现方式，而不是它的实际分辨率。
我在这里的问题是，我如何正确地支持肖像和景观方向，并将其正确地反映在视频文件输出中？我需要这些视频在所有平台上正确播放，所以我认为决议将非常重要。
下面是我迄今所写的全部资料。我很感激你们能给我的任何建议。
import UIKit
import AVFoundation
class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate {
//MARK: - Outlet
@IBOutlet weak var previewView: UIView!
@IBOutlet var playStopButton: UIButton!
//MARK: - Private Variables
let videoQueue = DispatchQueue(label: "VideoQueue", qos: .background, attributes: .concurrent, autoreleaseFrequency: .workItem, target: nil)
private let captureSession = AVCaptureSession()
var outputUrl: URL {
get {
if let url = _outputUrl {
return url
}
_outputUrl = outputDirectory.appendingPathComponent("video.mp4")
return _outputUrl!
}
}
private var _outputUrl: URL?
var outputDirectory: URL {
get {
if let url = _outputDirectory {
return url
}
_outputDirectory = getDocumentsDirectory().appendingPathComponent("recording")
return _outputDirectory!
}
}
private var _outputDirectory: URL?
private var assetWriter: AVAssetWriter?
private var videoInput: AVAssetWriterInput?
private var audioInput: AVAssetWriterInput?
private var videoOutput: AVCaptureVideoDataOutput?
private var audioOutput: AVCaptureAudioDataOutput?
private var isRecording = false
private var isWriting = false
private var videoSize = CGSize(width: 640, height: 480)
//MARK: - View Life-cycle
override func viewDidLoad() {
super.viewDidLoad()
videoQueue.async {
do {
try self.configureCaptureSession()
try self.configureAssetWriter()
DispatchQueue.main.async {
self.configurePreview()
}
} catch {
DispatchQueue.main.async {
self.showAlert("Unable to configure video output")
}
}
}
}
override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
return .portrait
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}
//MARK: - Capture Session
private func configureCaptureSession() throws {
do {
// configure the session
if captureSession.canSetSessionPreset(AVCaptureSessionPreset640x480) {
captureSession.sessionPreset = AVCaptureSessionPreset640x480
}
// configure capture devices
let camDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
let micDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeAudio)
let camInput = try AVCaptureDeviceInput(device: camDevice)
let micInput = try AVCaptureDeviceInput(device: micDevice)
if captureSession.canAddInput(camInput) {
captureSession.addInput(camInput)
}
if captureSession.canAddInput(micInput) {
captureSession.addInput(micInput)
}
// configure audio/video output
videoOutput = AVCaptureVideoDataOutput()
videoOutput?.alwaysDiscardsLateVideoFrames = false // TODO: is this necessary?
videoOutput?.setSampleBufferDelegate(self, queue: videoQueue)
if let v = videoOutput {
captureSession.addOutput(v)
}
audioOutput = AVCaptureAudioDataOutput()
audioOutput?.setSampleBufferDelegate(self, queue: videoQueue)
if let a = audioOutput {
captureSession.addOutput(a)
}
// configure audio session
let audioSession = AVAudioSession.sharedInstance()
try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord)
try audioSession.setActive(true)
var micPort: AVAudioSessionPortDescription?
if let inputs = audioSession.availableInputs {
for port in inputs {
if port.portType == AVAudioSessionPortBuiltInMic {
micPort = port
break;
}
}
}
if let port = micPort, let dataSources = port.dataSources {
for source in dataSources {
if source.orientation == AVAudioSessionOrientationFront {
try audioSession.setPreferredInput(port)
break
}
}
}
} catch {
print("Failed to configure audio/video capture session")
throw error
}
}
private func configureAssetWriter() throws {
prepareVideoFile()
do {
assetWriter = try AVAssetWriter(url: outputUrl, fileType: AVFileTypeMPEG4)
guard let writer = assetWriter else {
print("Asset writer not created")
return
}
let vidSize = videoSize
let videoSettings: [String: Any] = [AVVideoCodecKey: AVVideoCodecH264,
AVVideoWidthKey: NSNumber(value: Float(vidSize.width)),
AVVideoHeightKey: NSNumber(value: Float(vidSize.height))]
videoInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoSettings)
videoInput?.expectsMediaDataInRealTime = true
videoInput?.transform = getVideoTransform()
var channelLayout = AudioChannelLayout()
memset(&channelLayout, 0, MemoryLayout<AudioChannelLayout>.size);
channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
let audioSettings: [String: Any] = [AVFormatIDKey: kAudioFormatMPEG4AAC,
AVSampleRateKey: 44100,
AVNumberOfChannelsKey: 2]
audioInput = AVAssetWriterInput(mediaType: AVMediaTypeAudio, outputSettings: audioSettings)
audioInput?.expectsMediaDataInRealTime = true
guard let vi = videoInput else {
print("Video input not configured")
return
}
guard let ai = audioInput else {
print("Audio input not configured")
return
}
if writer.canAdd(vi) {
writer.add(vi)
}
if writer.canAdd(ai) {
writer.add(ai)
}
} catch {
print("Failed to configure asset writer")
throw error
}
}
private func prepareVideoFile() {
if FileManager.default.fileExists(atPath: outputUrl.path) {
do {
try FileManager.default.removeItem(at: outputUrl)
} catch {
print("Unable to remove file at URL \(outputUrl)")
}
}
if !FileManager.default.fileExists(atPath: outputDirectory.path) {
do {
try FileManager.default.createDirectory(at: outputDirectory, withIntermediateDirectories: true, attributes: nil)
} catch {
print("Unable to create directory at URL \(outputDirectory)")
}
}
}
private func configurePreview() {
if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
previewLayer.frame = previewView.bounds
previewView.layer.addSublayer(previewLayer)
}
}
private func getVideoSize() -> CGSize {
if UIDevice.current.orientation == .landscapeLeft || UIDevice.current.orientation == .landscapeRight {
if videoSize.width > videoSize.height {
return videoSize
} else {
return CGSize(width: videoSize.height, height: videoSize.width)
}
} else {
if videoSize.width < videoSize.height {
return videoSize
} else {
return CGSize(width: videoSize.height, height: videoSize.width)
}
}
}
private func getVideoTransform() -> CGAffineTransform {
switch UIDevice.current.orientation {
case .portraitUpsideDown:
return CGAffineTransform(rotationAngle: CGFloat((M_PI * -90.0)) / 180.0)
case .landscapeLeft:
return CGAffineTransform(rotationAngle: CGFloat((M_PI * -180.0)) / 180.0) // TODO: Add support for front facing camera
// return CGAffineTransform(rotationAngle: CGFloat((M_PI * 0.0)) / 180.0) // TODO: For front facing camera
case .landscapeRight:
return CGAffineTransform(rotationAngle: CGFloat((M_PI * 0.0)) / 180.0) // TODO: Add support for front facing camera
// return CGAffineTransform(rotationAngle: CGFloat((M_PI * -180.0)) / 180.0) // TODO: For front facing camera
default:
return CGAffineTransform(rotationAngle: CGFloat((M_PI * 90.0)) / 180.0)
}
}
//MARK: - Controls
private func startRecording() {
videoQueue.async {
self.captureSession.startRunning()
}
isRecording = true
playStopButton.setTitle("Stop Recording", for: .normal)
print("Recording did start")
}
private func stopRecording() {
if !isRecording {
return
}
videoQueue.async {
self.assetWriter?.finishWriting {
print("Asset writer did finish writing")
self.isWriting = false
}
self.captureSession.stopRunning()
}
isRecording = false
playStopButton.setTitle("Start Recording", for: .normal)
print("Recording did stop")
}
//MARK: - AVCaptureVideoDataOutputSampleBufferDelegate
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
guard let w = assetWriter else {
print("Asset writer not configured")
return
}
guard let vo = videoOutput else {
print("Video output not configured")
return
}
guard let ao = audioOutput else {
print("Audio output not configured")
return
}
guard let vi = videoInput else {
print("Video input not configured")
return
}
guard let ai = audioInput else {
print("Audio input not configured")
return
}
let st = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
print("Writer status \(w.status.rawValue)")
if let e = w.error {
print("Writer error \(e)")
stopRecording()
return
}
switch w.status {
case .unknown:
if !isWriting {
isWriting = true
w.startWriting()
w.startSession(atSourceTime: st)
}
return
case .completed:
print("Video writing completed")
return
case .cancelled:
print("Video writing cancelled")
return
case .failed:
print("Video writing failed")
return
default:
print("Video is writing")
}
if vo == captureOutput {
if !vi.append(sampleBuffer) {
print("Unable to write to video buffer")
}
} else if ao == captureOutput {
if !ai.append(sampleBuffer) {
print("Unable to write to audio buffer")
}
}
}
//MARK: Helpers
private func getDocumentsDirectory() -> URL {
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let documentsDirectory = paths[0]
return documentsDirectory
}
//MARK: Actions
@IBAction func startStopTapped(sender: AnyObject) {
if isRecording {
stopRecording()
} else {
startRecording()
}
}
}回答 4
Stack Overflow用户
回答已采纳
发布于 2019-07-11 12:47:52
视频方向由AVAssetWriterInput.transform处理，看起来getVideoTransform()实现不正确- CGAffineTransform希望旋转角度为弧度，因此需要更改为如下所示：
private func getVideoTransform() -> CGAffineTransform {
switch UIDevice.current.orientation {
case .portrait:
return .identity
case .portraitUpsideDown:
return CGAffineTransform(rotationAngle: .pi)
case .landscapeLeft:
return CGAffineTransform(rotationAngle: .pi/2)
case .landscapeRight:
return CGAffineTransform(rotationAngle: -.pi/2)
default:
return .identity
}
}苹果技术问答：index.html
如果使用
AVAssetWriter对象编写电影文件，则可以使用关联AVAssetWriterInput的transform属性指定输出文件方向。这将将显示转换属性写入输出文件，作为用于显示目的的可视媒体数据的首选转换。有关详细信息，请参阅AVAssetWriterInput.h接口文件。
Stack Overflow用户
发布于 2017-03-03 12:31:32
我已经找到了解决问题的办法。解决方案是使用AVAssetExportSession导出视频，以处理设置视频大小的问题，然后在输出时处理旋转，而不是在录制过程中。我仍然有一个问题，如果我需要修正的比例因素，从我原来的视频大小到一个更小的640x480分辨率，但至少我解决了我的轮换问题。请参阅下面更新的代码。
import UIKit
import AVFoundation
class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate {
//MARK: - Outlet
@IBOutlet weak var previewView: UIView!
@IBOutlet var playStopButton: UIButton!
//MARK: - Private Variables
let videoQueue = DispatchQueue(label: "VideoQueue", qos: .background, attributes: .concurrent, autoreleaseFrequency: .workItem, target: nil)
private let captureSession = AVCaptureSession()
var outputUrl: URL {
get {
if let url = _outputUrl {
return url
}
_outputUrl = outputDirectory.appendingPathComponent("video.mp4")
return _outputUrl!
}
}
private var _outputUrl: URL?
var exportUrl: URL {
get {
if let url = _exportUrl {
return url
}
_exportUrl = outputDirectory.appendingPathComponent("video_encoded.mp4")
return _exportUrl!
}
}
private var _exportUrl: URL?
var outputDirectory: URL {
get {
if let url = _outputDirectory {
return url
}
_outputDirectory = getDocumentsDirectory().appendingPathComponent("recording")
return _outputDirectory!
}
}
private var _outputDirectory: URL?
private var assetWriter: AVAssetWriter?
private var videoInput: AVAssetWriterInput?
private var audioInput: AVAssetWriterInput?
private var videoOutput: AVCaptureVideoDataOutput?
private var audioOutput: AVCaptureAudioDataOutput?
private var isRecording = false
private var isWriting = false
private var videoSize = CGSize(width: 640, height: 480)
private var exportPreset = AVAssetExportPreset640x480
//MARK: - View Life-cycle
override func viewDidLoad() {
super.viewDidLoad()
videoQueue.async {
do {
try self.configureCaptureSession()
DispatchQueue.main.sync {
self.configurePreview()
}
} catch {
DispatchQueue.main.async {
self.showAlert("Unable to configure capture session")
}
}
}
}
override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
return .portrait
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}
//MARK: - Capture Session
private func configureCaptureSession() throws {
do {
// configure capture devices
let camDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
let micDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeAudio)
let camInput = try AVCaptureDeviceInput(device: camDevice)
let micInput = try AVCaptureDeviceInput(device: micDevice)
if captureSession.canAddInput(camInput) {
captureSession.addInput(camInput)
}
if captureSession.canAddInput(micInput) {
captureSession.addInput(micInput)
}
// configure audio/video output
videoOutput = AVCaptureVideoDataOutput()
videoOutput?.alwaysDiscardsLateVideoFrames = false // TODO: is this necessary?
videoOutput?.setSampleBufferDelegate(self, queue: videoQueue)
if let v = videoOutput {
captureSession.addOutput(v)
}
audioOutput = AVCaptureAudioDataOutput()
audioOutput?.setSampleBufferDelegate(self, queue: videoQueue)
if let a = audioOutput {
captureSession.addOutput(a)
}
// configure audio session
let audioSession = AVAudioSession.sharedInstance()
try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord)
try audioSession.setActive(true)
var micPort: AVAudioSessionPortDescription?
if let inputs = audioSession.availableInputs {
for port in inputs {
if port.portType == AVAudioSessionPortBuiltInMic {
micPort = port
break;
}
}
}
if let port = micPort, let dataSources = port.dataSources {
for source in dataSources {
if source.orientation == AVAudioSessionOrientationFront {
try audioSession.setPreferredInput(port)
break
}
}
}
} catch {
print("Failed to configure audio/video capture session")
throw error
}
}
private func configureAssetWriter() throws {
prepareVideoFile()
do {
if assetWriter != nil {
assetWriter = nil
videoInput = nil
audioInput = nil
}
assetWriter = try AVAssetWriter(url: outputUrl, fileType: AVFileTypeMPEG4)
guard let writer = assetWriter else {
print("Asset writer not created")
return
}
let videoSettings: [String: Any] = [AVVideoCodecKey: AVVideoCodecH264,
AVVideoWidthKey: NSNumber(value: Float(videoSize.width)),
AVVideoHeightKey: NSNumber(value: Float(videoSize.height))]
videoInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoSettings)
videoInput?.expectsMediaDataInRealTime = true
var channelLayout = AudioChannelLayout()
memset(&channelLayout, 0, MemoryLayout<AudioChannelLayout>.size);
channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
let audioSettings: [String: Any] = [AVFormatIDKey: kAudioFormatMPEG4AAC,
AVSampleRateKey: 44100,
AVNumberOfChannelsKey: 2]
audioInput = AVAssetWriterInput(mediaType: AVMediaTypeAudio, outputSettings: audioSettings)
audioInput?.expectsMediaDataInRealTime = true
guard let vi = videoInput else {
print("Video input not configured")
return
}
guard let ai = audioInput else {
print("Audio input not configured")
return
}
if writer.canAdd(vi) {
writer.add(vi)
}
if writer.canAdd(ai) {
writer.add(ai)
}
} catch {
print("Failed to configure asset writer")
throw error
}
}
private func prepareVideoFile() {
if FileManager.default.fileExists(atPath: outputUrl.path) {
do {
try FileManager.default.removeItem(at: outputUrl)
} catch {
print("Unable to remove file at URL \(outputUrl)")
}
}
if !FileManager.default.fileExists(atPath: outputDirectory.path) {
do {
try FileManager.default.createDirectory(at: outputDirectory, withIntermediateDirectories: true, attributes: nil)
} catch {
print("Unable to create directory at URL \(outputDirectory)")
}
}
}
private func configurePreview() {
if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
previewLayer.frame = previewView.bounds
previewView.layer.addSublayer(previewLayer)
}
}
private func getVideoSize() -> CGSize {
if UIDevice.current.orientation == .landscapeLeft || UIDevice.current.orientation == .landscapeRight {
if videoSize.width > videoSize.height {
return videoSize
} else {
return CGSize(width: videoSize.height, height: videoSize.width)
}
} else {
if videoSize.width < videoSize.height {
return videoSize
} else {
return CGSize(width: videoSize.height, height: videoSize.width)
}
}
}
//MARK: - Controls
private func startRecording() {
videoQueue.async {
do {
try self.configureAssetWriter()
self.captureSession.startRunning()
} catch {
print("Unable to start recording")
DispatchQueue.main.async { self.showAlert("Unable to start recording") }
}
}
isRecording = true
playStopButton.setTitle("Stop Recording", for: .normal)
print("Recording did start")
}
private func stopRecording() {
if !isRecording {
return
}
videoQueue.async {
self.assetWriter?.finishWriting {
print("Asset writer did finish writing")
self.isWriting = false
}
self.captureSession.stopRunning()
do {
try self.export()
} catch {
print("Export failed")
DispatchQueue.main.async { self.showAlert("Unable to export video") }
}
}
isRecording = false
playStopButton.setTitle("Start Recording", for: .normal)
print("Recording did stop")
}
//MARK: - AVCaptureVideoDataOutputSampleBufferDelegate
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
guard let w = assetWriter else {
print("Asset writer not configured")
return
}
guard let vo = videoOutput else {
print("Video output not configured")
return
}
guard let ao = audioOutput else {
print("Audio output not configured")
return
}
guard let vi = videoInput else {
print("Video input not configured")
return
}
guard let ai = audioInput else {
print("Audio input not configured")
return
}
let st = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
print("Writer status \(w.status.rawValue)")
if let e = w.error {
print("Writer error \(e)")
stopRecording()
return
}
switch w.status {
case .unknown:
if !isWriting {
isWriting = true
w.startWriting()
w.startSession(atSourceTime: st)
}
return
case .completed:
print("Video writing completed")
return
case .cancelled:
print("Video writing cancelled")
return
case .failed:
print("Video writing failed")
return
default:
print("Video is writing")
}
if vo == captureOutput {
if !vi.append(sampleBuffer) {
print("Unable to write to video buffer")
}
} else if ao == captureOutput {
if !ai.append(sampleBuffer) {
print("Unable to write to audio buffer")
}
}
}
//MARK: - Export
private func getVideoComposition(asset: AVAsset, videoSize: CGSize) -> AVMutableVideoComposition? {
guard let videoTrack = asset.tracks(withMediaType: AVMediaTypeVideo).first else {
print("Unable to get video tracks")
return nil
}
let videoComposition = AVMutableVideoComposition()
videoComposition.renderSize = videoSize
let seconds: Float64 = Float64(1.0 / videoTrack.nominalFrameRate)
videoComposition.frameDuration = CMTimeMakeWithSeconds(seconds, 600);
let layerInst = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
var transforms = asset.preferredTransform
var isPortrait = true;
if (transforms.a == 0.0 && transforms.b == 1.0 && transforms.c == -1.0 && transforms.d == 0)
|| (transforms.a == 0.0 && transforms.b == -1.0 && transforms.c == 1.0 && transforms.d == 0) {
isPortrait = false;
}
if isPortrait {
transforms = transforms.concatenating(CGAffineTransform(rotationAngle: CGFloat(90.0.degreesToRadians)))
transforms = transforms.concatenating(CGAffineTransform(translationX: videoSize.width, y: 0))
}
layerInst.setTransform(transforms, at: kCMTimeZero)
let inst = AVMutableVideoCompositionInstruction()
inst.backgroundColor = UIColor.black.cgColor
inst.layerInstructions = [layerInst]
inst.timeRange = CMTimeRange(start: kCMTimeZero, duration: asset.duration)
videoComposition.instructions = [inst]
return videoComposition
}
private func export() throws {
let videoAsset = AVURLAsset(url: outputUrl)
if FileManager.default.fileExists(atPath: exportUrl.path) {
try FileManager.default.removeItem(at: exportUrl)
}
let videoSize = getVideoSize()
guard let encoder = AVAssetExportSession(asset: videoAsset, presetName: exportPreset) else {
print("Unable to create encoder")
return
}
guard let vidcomp = getVideoComposition(asset: videoAsset, videoSize: videoSize) else {
print("Unable to create video composition")
return
}
encoder.videoComposition = vidcomp
encoder.outputFileType = AVFileTypeMPEG4 // MP4 format
encoder.outputURL = exportUrl
encoder.shouldOptimizeForNetworkUse = true
encoder.exportAsynchronously(completionHandler: {
print("Video exported successfully")
})
}
//MARK: Helpers
private func getDocumentsDirectory() -> URL {
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let documentsDirectory = paths[0]
return documentsDirectory
}
//MARK: Actions
@IBAction func startStopTapped(sender: AnyObject) {
if isRecording {
stopRecording()
} else {
startRecording()
}
}
}Stack Overflow用户
发布于 2020-10-07 08:20:59
我发现最简单的方法是根据所需的方向在视频组合轨道上设置preferredTransform。
溶液
// Devices orientation
var orientation = UIDevice.current.orientation
// The composition
let audioVideoComposition = AVMutableComposition()
// The video track of the composition
let videoCompositionTrack = audioVideoComposition
.addMutableTrack(withMediaType: .video, preferredTrackID: .init())!
// Set preferred transform
videoCompositionTrack.preferredTransform = getVideoTransform()辅助函数与扩展
func getVideoTransform() -> CGAffineTransform {
switch orientation {
case .portrait:
return CGAffineTransform(rotationAngle: 90.degreesToRadians)
case .portraitUpsideDown:
return CGAffineTransform(rotationAngle: 180)
case .landscapeLeft:
return CGAffineTransform(rotationAngle: 0.degreesToRadians)
case .landscapeRight:
return CGAffineTransform(rotationAngle: 180.degreesToRadians)
default:
return CGAffineTransform(rotationAngle: 90.degreesToRadians)
}
}
extension BinaryInteger {
var degreesToRadians: CGFloat { CGFloat(self) * .pi / 180 }
}
extension FloatingPoint {
var degreesToRadians: Self { self * .pi / 180 }
var radiansToDegrees: Self { self * 180 / .pi }
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/42554122
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