Ios CGContext将文本倒置

我使用CGContext呈现NSAttributed字符串，但是当它呈现文本时，文本是颠倒的：(

这就是我想到的：

override func draw(with box: PDFDisplayBox, in context: CGContext) {

        UIGraphicsPushContext(context)
        context.saveGState()

        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.alignment = .center

        let attributes = [
            NSAttributedString.Key.paragraphStyle: paragraphStyle,
            NSAttributedString.Key.font: UIFont.systemFont(ofSize: 80.0),
            NSAttributedString.Key.foregroundColor: UIColor.red
        ]

        NSAttributedString(string: self.widgetStringValue!, attributes: attributes).draw(in: self.bounds)


        context.restoreGState()
        UIGraphicsPopContext()

    }

我尝试添加以下内容：

context.translateBy(x: 0.0, y: bounds.height)  
context.scaleBy(x: 1.0, y: -1.0)

但是，我的屏幕上根本没有显示文本：(

我做错了什么

更新

根据要求，这里是我的完整TextAnnotation类：

class TextAnnotation:  PDFAnnotation {

    var currentText: String?

    override init(bounds: CGRect, forType annotationType: PDFAnnotationSubtype, withProperties properties: [AnyHashable : Any]?) {
        super.init(bounds: bounds, forType: annotationType, withProperties: properties)

        self.widgetFieldType = PDFAnnotationWidgetSubtype(rawValue: PDFAnnotationWidgetSubtype.text.rawValue)

        self.font = UIFont.systemFont(ofSize: 80)

        self.isMultiline = true

        self.widgetStringValue = "Text Here"

        self.currentText = self.widgetStringValue!
    }

    override func draw(with box: PDFDisplayBox, in context: CGContext) {
        UIGraphicsPushContext(context)
        context.saveGState()

        let pageBounds = bounds
        context.translateBy(x: 0, y: pageBounds.height)
        context.scaleBy(x: 1, y: -1)

        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.alignment = .center

        let attributes: [NSAttributedString.Key: Any] = [
            .paragraphStyle: paragraphStyle,
            .font: UIFont.systemFont(ofSize: 80),
            .foregroundColor: UIColor.red
        ]

        widgetStringValue!.draw(in: pageBounds, withAttributes: attributes)

        context.restoreGState()
        UIGraphicsPopContext()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

---

在

PDFanRotation

中，您只需添加

translateBy（x:y:）

和

scaledBy（x:y:）

，如前所述：

override func draw(with box: PDFDisplayBox, in context: CGContext) {
    UIGraphicsPushContext(context)
    context.saveGState()

    context.translateBy(x: 0, y: bounds.height)
    context.scaleBy(x: 1, y: -1)

    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.alignment = .center

    let attributes: [NSAttributedString.Key: Any] = [
        .paragraphStyle:  paragraphStyle,
        .font:            UIFont.systemFont(ofSize: 80),
        .foregroundColor: UIColor.red
    ]

    widgetStringValue?.draw(in: bounds, withAttributes: attributes)

    context.restoreGState()
    UIGraphicsPopContext()
}

---

在

PDFPage

中，您应该使用来获取

PDFDisplayBox

中的边界，然后使用

translateBy（x:y:）

和

scaledBy（x:y:）

，正如您所讨论的：

override func draw(with box: PDFDisplayBox, to context: CGContext) {
    UIGraphicsPushContext(context)
    context.saveGState()

    let pageBounds = bounds(for: box)
    context.translateBy(x: 0, y: pageBounds.height)
    context.scaleBy(x: 1, y: -1)

    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.alignment = .center

    let attributes: [NSAttributedString.Key: Any] = [
        .paragraphStyle:  paragraphStyle,
        .font:            UIFont.systemFont(ofSize: 80),
        .foregroundColor: UIColor.red
    ]

    text.draw(in: pageBounds, withAttributes: attributes)

    context.restoreGState()
    UIGraphicsPopContext()
}

---

在我的例子中，我对一个PDFanRotation进行了子类化。关键是在我的draw方法中为translateBy调用使用了正确的y值（这很难理解）：

override func draw(with box: PDFDisplayBox, in context: CGContext) {
    let text = NSString(string: "Hello!")

    UIGraphicsPushContext(context)
    context.saveGState()

    context.translateBy(x: 0, y: bounds.height + (2 * bounds.minY))
    context.scaleBy(x: 1, y: -1.0)
    text.draw(in: bounds.offsetBy(dx: 2, dy: 0), withAttributes: attributes)

    context.restoreGState()
    UIGraphicsPopContext()
}

---

代码中有一个错误：无法在此行上调用非函数类型“CGRect”的值：让pageBounds=bounds（for:box）我假设您使用的是

PDFPage

，但现在回想起来，情况显然不是这样。我建议您编辑您的问题（a）显示完整的类；以及（b）你是如何使用它的。例如，我猜你正在做一个

PDFanRotation

？不管它是什么，请向我们展示你如何创建和使用它的代码。现在回想起来，这个问题有点不清楚。但是上面两个都对我有用，正确地翻转它，所以请帮助我重现你的问题。