Question

我初始化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：
如何在屏幕上显示所有CGSize图层所需的确切captureVideoPreviewLayer？更准确地说，我需要AVLayerVideoGravityResizeAspect的高度使AVCaptureVideoPreviewLayer适合preview.size？
我尝试获得适合的AVCaptureVideoPreviewLayer尺寸。

非常感谢你的帮助

Answer 1

经过AVCaptureSessionPresetPhoto的一些研究后，AVCaptureVideoPreviewLayer尊重iPhone相机的3/4比例。因此，通过简单的微积分很容易获得正确的高度例如，如果宽度 320 ，则适当的高度为：
320 * 4/3 = <强> 426.6

Answer 2

如果我理解正确，你会尝试获得宽度和宽度。当前视频会话的高度您可以从AVCaptureOutput的outputSettings字典中获取它们。（使用AVVideoWidthKey＆amp; AVVideoHeightKey）。

e.g。

NSDictionary* outputSettings = [movieFileOutput outputSettingsForConnection:videoConnection];
CGSize videoSize = NSMakeSize([[outputSettings objectForKey:AVVideoWidthKey] doubleValue], [[outputSettings objectForKey:AVVideoHeightKey] doubleValue]);

<强>更新
另一个想法是从预览会话的图像缓冲区中获取帧大小实现AVCaptureVideoDataOutputSampleBufferDelegate方法captureOutput:didOutputSampleBuffer:fromConnection: （不要忘记设置AVCaptureOutput的委托）

- (void)captureOutput:(AVCaptureFileOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
{
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    if(imageBuffer != NULL)
    {
        CGSize imageSize = CVImageBufferGetDisplaySize(imageBuffer);
        NSLog(@"%@", NSStringFromSize(imageSize));
    }
}

Answer 3

Weischel的代码对我不起作用。这个想法奏效了，但代码却没有。这是有效的代码：

    // 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);

Answer 4

感谢gsempe的回答。我从小时起就遇到了同样的问题:) 我用这个代码解决了它，以横向模式将其置于屏幕中：

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（）函数才能在屏幕中显示居中图层。

谢谢，

儒略

AVCaptureSession预设照片和AVCaptureVideoPreviewLayer尺寸

4 个答案: