MacOS: Add a text overlay to an image in Swift

问题

I've written a small extension for UIImage, which adds a text to an image:

extension UIImage {

    func addTextToImage(textToAdd: String) -> UIImage {
        let textColor = UIColor.white
        let textFont = UIFont(name: "Snell Roundhand", size: 40)!
        let scale = UIScreen.main.scale
        UIGraphicsBeginImageContextWithOptions(self.size, false, scale)

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

        var textFontAttributes = [
            NSAttributedString.Key.font: textFont,
            NSAttributedString.Key.foregroundColor: textColor,
            NSAttributedString.Key.paragraphStyle: paragraphStyle
            ] as [NSAttributedString.Key : Any]


        self.draw(in: CGRect(origin: CGPoint.zero, size: self.size))
        let textFrame = CGPoint(x: self.size.width/4, y: self.size.height/4)
        let rect = CGRect(origin: textFrame, size: CGSize(width: self.size.width/2, height: self.size.height/2) )
        text.draw(in: rect, withAttributes: textFontAttributes)

        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage!
    }
}

The result should look like this:

Now I want to do the same thing for NSImage to run on MacOS.

Any ideas how to do this?

All similar questions on Stackoverflow are either very old, unanswered or in Objective C

回答1:

Found a solution:

extension NSImage {

    func addTextToImage(drawText text: String) -> NSImage {

        let targetImage = NSImage(size: self.size, flipped: false) { (dstRect: CGRect) -> Bool in

            self.draw(in: dstRect)
            let textColor = NSColor.white
            let textFont = NSFont(name: "Snell Roundhand", size: 36)! //Helvetica Bold
            let paragraphStyle = NSMutableParagraphStyle()
            paragraphStyle.alignment = NSTextAlignment.center

            var textFontAttributes = [
                NSAttributedString.Key.font: textFont,
                NSAttributedString.Key.foregroundColor: textColor,
                ] as [NSAttributedString.Key : Any]

            let textOrigin = CGPoint(x: self.size.height/3, y: -self.size.width/4)
            let rect = CGRect(origin: textOrigin, size: self.size)
            text.draw(in: rect, withAttributes: textFontAttributes)
            return true
        }
        return targetImage
    }
}

来源：https://stackoverflow.com/questions/54450429/macos-add-a-text-overlay-to-an-image-in-swift