NSLayoutConstraints可以用十进制常量呈现吗?

我在UIScrollView中创建了几个uiview,它们根据我在Height和Width文本字段中键入的值动态调整大小。调整UIView的大小后,我将UIScrollView的内容保存为PDF数据。

我发现PDF中UIView的维度(在Adobe Illustrator中测量时)总是四舍五入到三分之一。

例如:

1.5->1.333

1.75->1.666

每次更新约束之前我都会检查常量值,并且它们是准确的。有谁能解释一下为什么UIViews在作为PDF呈现时有不正确的维度?

@IBAction func updateDimensions(_ sender: Any) {

        guard let length = NumberFormatter().number(from:
            lengthTextField.text ?? "") else { return }

        guard let width = NumberFormatter().number(from:
            widthTextField.text ?? "") else { return }

        guard let height = NumberFormatter().number(from:
            heightTextField.text ?? "") else { return }

        let flapHeight = CGFloat(truncating: width)/2

        let lengthFloat = CGFloat(truncating: length)
        let widthFloat = CGFloat(truncating: width)
        let heightFloat = CGFloat(truncating: height)

        UIView.animate(withDuration: 0.3) {
            self.faceAWidthConstraint.constant = lengthFloat
            self.faceAHeightConstraint.constant = heightFloat
            self.faceBWidthConstraint.constant = widthFloat
            self.faceA1HeightConstraint.constant = flapHeight
            self.view.layoutIfNeeded()
        }
    }

    func createPDFfrom(aView: UIView, saveToDocumentsWithFileName fileName: String)
    {
        let pdfData = NSMutableData()
        UIGraphicsBeginPDFContextToData(pdfData, aView.bounds, nil)
        UIGraphicsBeginPDFPage()

        guard let pdfContext = UIGraphicsGetCurrentContext() else { return }

        aView.layer.render(in: pdfContext)
        UIGraphicsEndPDFContext()

        if let documentDirectories = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first {
            let documentsFileName = documentDirectories + "/" + fileName
            debugPrint(documentsFileName)
            pdfData.write(toFile: documentsFileName, atomically: true)
        }
    }