Swift3 为动态缩小的图像设置约束。敏捷的

我有一个相当大的徽标（58312x1478px），我正在使用alamofire图像缩小它的大小，然后使用可视流布局（VFL）设置约束，使其在视图（self.view）中水平和垂直居中，如下所示。 由于以下限制，徽标没有居中，请有人告诉我哪里出了问题

let viewWidth   =   self.view.bounds.width
let viewHeight  =   self.view.bounds.height


let logoView               =    UIImageView()
logoView.translatesAutoresizingMaskIntoConstraints = false

let logo                        =   UIImage(named: "logo")
let logoSize                    =   CGSize(width: 200.0, height: 100.0)
let aspectScaledToFitImage      =   logo.af_imageAspectScaled(toFit: logoSize)

logoView.image                  =   aspectScaledToFitImage
self.view.addSubview(logoView)

let logoHeight         =    logoView.frame.size.height
let logoWidth          =    logoView.frame.size.width

let logoViewTopSpacing     =   (viewHeight / 2) + (logoHeight / 2)
let logoViewSideSpacing    =   (viewWidth / 2) + (logoWidth / 2)


let views = [
    "logoView"     :   logoView
]

// SETTING CONSTRAINTS
view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-\(logoViewSideSpacing)-[logoView]", options: [], metrics: nil, views: views))
view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-\(logoViewTopSpacing)-[logoView]", options: [], metrics: nil, views: views))

我知道了

通过替换下面的

let imageWidth         =    aspectScaledToFitImage.size.width
let imageHeight         =    aspectScaledToFitImage.size.height


let logoViewTopSpacing     =   (viewHeight / 2) - (imageHeight / 2)
let logoViewSideSpacing    =   (viewWidth / 2) - (imageWidth / 2)

与

解决了徽标在视图中居中的问题

let logoHeight         =    logoView.frame.size.height
let logoWidth          =    logoView.frame.size.width

let logoViewTopSpacing     =   (viewHeight / 2) + (logoHeight / 2)
let logoViewSideSpacing    =   (viewWidth / 2) + (logoWidth / 2)