Objective c AVCaptureSession预设照片和AVCaptureVideoPreviewLayer大小

我初始化了一个

AVCaptureSession

，并将其预设为：

AVCaptureSession *newCaptureSession = [[AVCaptureSession alloc] init];
if (YES==[newCaptureSession canSetSessionPreset:AVCaptureSessionPresetPhoto]) {
    newCaptureSession.sessionPreset = AVCaptureSessionPresetPhoto;
} else {
    // Error management
}

然后我设置了一个

AVCaptureVideoPreviewLayer

：

self.preview = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height/*426*/)];
CALayer *previewLayer = preview.layer;
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
captureVideoPreviewLayer.frame = previewLayer.frame;
[previewLayer addSublayer:captureVideoPreviewLayer];
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspect;

我的问题是：
如何获得在屏幕上显示所有

captureVideoPreviewLayer

层所需的确切

CGSize

？更准确地说，我需要的高度是

AVLayerVideoGravityResizeAspect

使

AVCaptureVideoPreviewLayer

适合

预览。大小

？

---

我尝试获得合适的AVCaptureVideoPreviewLayer大小。

---

非常感谢您的帮助

如果我理解正确，请尝试获取当前视频会话的宽度和高度。
您可以从

AVCaptureOutput

的outputSettings字典中获取它们。（使用

AVVideoWidthKey

和

AVVideoHeightKey

）

e、 g

更新：
另一个想法是从预览会话的图像缓冲区获取帧大小。
实现AVCaptureVideoDataOutputSampleBufferDelegate方法

captureOutput:didOutputSampleBuffer:fromConnection:

（不要忘记设置AVCaptureOutput的委托）

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在使用AVCaptureSessionPresetPhoto进行一些研究后，AVCaptureVideoPreviewLayer尊重iPhone摄像头的3/4比例。因此，用简单的微积分很容易得到正确的高度。
例如，如果宽度为320，则适当的高度为：

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320*4/3=426.6Weischel的代码不适合我。这个想法行得通，但代码行不通。以下是确实有效的代码：

    // Get your AVCaptureSession somehow. I'm getting mine out of self.videoCamera, which is a GPUImageVideoCamera
    // Get the appropriate AVCaptureVideoDataOutput out of the capture session. I only have one session, so it's easy.

    AVCaptureVideoDataOutput *output = [[[self.videoCamera captureSession] outputs] lastObject];
    NSDictionary* outputSettings = [output videoSettings];

    // AVVideoWidthKey and AVVideoHeightKey did not work. I had to use these literal keys.
    long width  = [[outputSettings objectForKey:@"Width"]  longValue]; 
    long height = [[outputSettings objectForKey:@"Height"] longValue];

    // video camera output dimensions are always for landscape mode. Transpose if your camera is in portrait mode.
    if (UIInterfaceOrientationIsPortrait([self.videoCamera outputImageOrientation])) {
        long buf = width;
        width = height;
        height = buf;
    }

    CGSize outputSize = CGSizeMake(width, height);

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感谢gsempe为您提供的答案。我从几小时前开始就遇到同样的问题：） 我用这段代码解决了这个问题，以横向模式将它放在屏幕中央：

CGRect layerRect = [[[self view] layer] bounds];
[PreviewLayer setBounds:CGRectMake(0, 0, 426.6, 320)];
[PreviewLayer setPosition:CGPointMake(CGRectGetMidY(layerRect), CGRectGetMidX(layerRect))];

请注意，我必须反转CGRectGetMidY（）和CGRectGetMidX（）函数，以便在屏幕中有一个居中层

谢谢

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朱利安

我尝试获取AVCaptureVideoPreviewLayer的大小。因为我只设置了一个stillImageoutput outputSettings，所以只提供了：avVideoCodeKey=jpeg；我更新了我的答案。也许你可以从预览图像中获得尺寸。使用AVCaptureSessionPresetPhoto进行一些研究后，AVCaptureVideoPreviewLayer尊重iPhone相机的3/4比例。所以用简单的微积分很容易得到正确的高度。不过，谢谢你的帮助

    // Get your AVCaptureSession somehow. I'm getting mine out of self.videoCamera, which is a GPUImageVideoCamera
    // Get the appropriate AVCaptureVideoDataOutput out of the capture session. I only have one session, so it's easy.

    AVCaptureVideoDataOutput *output = [[[self.videoCamera captureSession] outputs] lastObject];
    NSDictionary* outputSettings = [output videoSettings];

    // AVVideoWidthKey and AVVideoHeightKey did not work. I had to use these literal keys.
    long width  = [[outputSettings objectForKey:@"Width"]  longValue]; 
    long height = [[outputSettings objectForKey:@"Height"] longValue];

    // video camera output dimensions are always for landscape mode. Transpose if your camera is in portrait mode.
    if (UIInterfaceOrientationIsPortrait([self.videoCamera outputImageOrientation])) {
        long buf = width;
        width = height;
        height = buf;
    }

    CGSize outputSize = CGSizeMake(width, height);

CGRect layerRect = [[[self view] layer] bounds];
[PreviewLayer setBounds:CGRectMake(0, 0, 426.6, 320)];
[PreviewLayer setPosition:CGPointMake(CGRectGetMidY(layerRect), CGRectGetMidX(layerRect))];