AVFoundation相机捕获缩放照片问题

Question

下面我已经粘贴了缩放模块的代码.缩放也有点眩晕,捕获的照片的结果图像不是根据缩放,即结果图像稍微放大.可以有人指导我.谢谢

func pinchToZoom(sender:UIPinchGestureRecognizer){

    if(sender.state == .Began){
        scale = sender.scale
    }

    if(sender.state == .Began || sender.state == .Changed){

        //NEW
        var effectiveScale = scale * sender.scale
        if(effectiveScale < 1.0){
            effectiveScale = 1.0
        }
        let maxScale = self.imageOutput.connectionWithMediaType(AVMediaTypeVideo).videoMaxScaleAndCropFactor

        if(effectiveScale > maxScale){
            effectiveScale = maxScale
        }

        //Transform
        CATransaction.begin()
        CATransaction.setAnimationDuration(0.25)
        let transform = CGAffineTransformMakeScale(effectiveScale, effectiveScale)
        cameraView.transform = transform
        CATransaction.commit()

        scale = sender.scale // Store the previous scale factor for the next pinch gesture call

        do {
            try device.lockForConfiguration()
            device.videoZoomFactor = effectiveScale
            device.unlockForConfiguration()
        } catch {
            print(error)
        }
    }
}