AVCaptureVideoPreviewLayer并从相机位置预览

Question

我正在开发一个允许用户拍照的应用程序.我已经开始使用AVCam apple提供但我实际上有一个问题简单地说我无法将相机层定位在我想要的位置但是它自动定位在View的中心

在左侧,您可以看到我实际拥有的东西,右侧是我想拥有的东西.包含来自摄像头的预览的视图是UIView子类,这是代码

class AVPreviewView : UIView {
    override class func layerClass() -> AnyClass {
        return AVCaptureVideoPreviewLayer.self
    }
    func session () -> AVCaptureSession {
        return (self.layer as AVCaptureVideoPreviewLayer).session
    }

    func setSession(session : AVCaptureSession) -> Void {
        (self.layer as AVCaptureVideoPreviewLayer).session = session;
        (self.layer as AVCaptureVideoPreviewLayer).videoGravity = AVLayerVideoGravityResizeAspect;

    }
}

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Answer 1

首先获取屏幕大小,以便计算宽高比

    let screenWidth = UIScreen.mainScreen().bounds.size.width
    let screenHeight = UIScreen.mainScreen().bounds.size.height
    var aspectRatio: CGFloat = 1.0

    var viewFinderHeight: CGFloat = 0.0
    var viewFinderWidth: CGFloat = 0.0
    var viewFinderMarginLeft: CGFloat = 0.0
    var viewFinderMarginTop: CGFlaot = 0.0

现在计算预览图层的大小.

    func setSession(session : AVCaptureSession) -> Void {

        if screenWidth > screenHeight {
            aspectRatio = screenHeight / screenWidth * aspectRatio
            viewFinderWidth = self.bounds.width
            viewFinderHeight = self.bounds.height * aspectRatio
            viewFinderMarginTop *= aspectRatio
        } else {
            aspectRatio = screenWidth / screenHeight
            viewFinderWidth = self.bounds.width * aspectRatio
            viewFinderHeight = self.bounds.height
            viewFinderMarginLeft *= aspectRatio
        }

        (self.layer as AVCaptureVideoPreviewLayer).session = session;

将图层设置为videoGravity,AVLayerVideoGravityResizeAspectFill以便在给定自定义视图的情况下图层会拉伸以填充.

        (self.layer as AVCaptureVideoPreviewLayer).videoGravity = AVLayerVideoGravityResizeAspectFill;

最后,将预览图层的框架设置为上面计算的值,使用您喜欢的任何偏移量.

        (self.layer as AVCaptureVideoPreviewLayer).frame = CGRectMake(viewFinderMarginLeft, viewFinderMarginTop, viewFinderWidth, viewFinderHeight)

    }

这可能需要一些调整,因为我还没有测试它,但你应该能够创建一个更灵活的VideoPreviewArea由APPreviewView的边界分隔.