AVCaptureVideoPreviewLayer 没有填满屏幕

Posted 2023-03-10

【中文标题】AVCaptureVideoPreviewLayer 没有填满屏幕

【英文标题】：AVCaptureVideoPreviewLayer not filling screen

【发布时间】：2013-04-26 09:59:39

【问题描述】：

我阅读了大约 100 万条关于如何使 VideoPreviewLayer 填充 iPhone 的整个屏幕的帖子，但没有任何效果......也许你可以帮助我，因为我真的被卡住了。

这是我的预览层初始化：

    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)

    // Choosing bigger preset for bigger screen.
    _sessionPreset = AVCaptureSessionPreset1280x720;

else

    _sessionPreset = AVCaptureSessionPresetHigh;


[self setupAVCapture];

AVCaptureSession *captureSession = _session;
AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:captureSession];
UIView *aView = self.view;
previewLayer.frame = aView.bounds;
previewLayer.connection.videoOrientation = AVCaptureVideoOrientationLandscapeRight;
[aView.layer addSublayer:previewLayer];

这就是我的 setupAvCapture 方法：

  //-- Setup Capture Session.
_session = [[AVCaptureSession alloc] init];
[_session beginConfiguration];

//-- Set preset session size.
[_session setSessionPreset:_sessionPreset];

//-- Creata a video device and input from that Device.  Add the input to the capture session.
AVCaptureDevice * videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if(videoDevice == nil)
    assert(0);

//-- Add the device to the session.
NSError *error;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
if(error)
    assert(0);

[_session addInput:input];

//-- Create the output for the capture session.
AVCaptureVideoDataOutput * dataOutput = [[AVCaptureVideoDataOutput alloc] init];
[dataOutput setAlwaysDiscardsLateVideoFrames:YES]; // Probably want to set this to NO when recording

//-- Set to YUV420.
[dataOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange]
                                                         forKey:(id)kCVPixelBufferPixelFormatTypeKey]]; // Necessary for manual preview

// Set dispatch to be on the main thread so OpenGL can do things with the data
[dataOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];

[_session addOutput:dataOutput];
[_session commitConfiguration];

[_session startRunning];

我已经尝试使用不同的 AVCaptureSessionPresets 和 ResizeFit 选项。但它总是看起来像这样：

http://imageshack.us/photo/my-images/707/img0013g.png/

或者如果我使用 previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;如果我记录图层的大小，则会返回正确的全屏大小。

http://imageshack.us/photo/my-images/194/img0014k.png/

【问题讨论】：

如果我设置 previewLayer.frame = CGRectMake(0, 0, 1280, 720);手动它正在工作......任何人都可以解释一下。似乎宽度/高度被翻转（纵向），但方向实际上是横向。所以我可以解决实现 _screenWidth = [UIScreen mainScreen].bounds.size.width; _screenHeight = [UIScreen mainScreen].bounds.size.height;如果（_screenHeight > _screenWidth） _screenWidth = _screenHeight; _screenHeight = [UIScreen mainScreen].bounds.size.width;

【参考方案1】：

尝试：

AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [AVCaptureVideoPreviewLayer layerWithSession: self.session];
[captureVideoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

快速更新

let previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill

Swift 4.0 更新

let previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill

【讨论】：

这在第一次加载时有效。但是在轮换时重新应用这似乎并没有必要。

也许你应该停止相机预览的旋转。在要放置的按钮的预览上创建一个透明视图，并使其旋转。我认为旋转相机预览有点有趣，上面是正确的答案。 :)

【参考方案2】：

如果有人遇到这个问题，你只需要抓住屏幕的边界

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer.frame = UIScreen.main.bounds
    previewLayer.videoGravity = .resizeAspectFill
    camPreview.layer.addSublayer(previewLayer)

【参考方案3】：

            videoPreviewLayer = AVCaptureVideoPreviewLayer(session: session)
            DispatchQueue.main.async 
                self.videoPreviewLayer?.frame = self.captureImageView.bounds
            
            cropImageRect = captureImageView.frame
            videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
            videoPreviewLayer?.connection?.videoOrientation = AVCaptureVideoOrientation.portrait
            captureImageView.layer.addSublayer(videoPreviewLayer!)
            session!.startRunning()

这对我有用。我面临的问题是，我将以下行放在主线程之外。它造成了我认为的问题。

self.videoPreviewLayer?.frame = self.captureImageView.bounds

【参考方案4】：

Swift 5 和 Xcode13

这对我有用

创建 AVCapturePreviewLayer

    class ViewController: UIViewController 
         let previewLayer = AVCapturePreviewLayer()
    

将 PreviewLayer 添加到视图中

    override func viewDidLoad() 
           super.viewDidLoad()
    // Adds Element to the View Layer
           view.layer.addSublayer(previewLayer)

使 PreviewLayer 成为 View 的完整边界

    override func viewDidLayoutSubviews() 
    super.viewDidLayoutSubviews()
    previewLayer.frame = view.bounds