Я огляделся и не смог понять, как взять текст, наложить его на изображение, а затем объединить два в одно UIImage.

Я исчерпал Google, используя поисковые запросы, которые я могу придумать, поэтому, если у кого-то есть решение или, по крайней мере, подсказка, на которую они могут указать, были бы очень признательны.

Хорошо ... Разобрался:

func textToImage(drawText: NSString, inImage: UIImage, atPoint: CGPoint) -> UIImage{

    // Setup the font specific variables
    var textColor = UIColor.whiteColor()
    var textFont = UIFont(name: "Helvetica Bold", size: 12)!

    // Setup the image context using the passed image
    let scale = UIScreen.mainScreen().scale
    UIGraphicsBeginImageContextWithOptions(inImage.size, false, scale)

    // Setup the font attributes that will be later used to dictate how the text should be drawn
    let textFontAttributes = [
        NSFontAttributeName: textFont,
        NSForegroundColorAttributeName: textColor,
    ]

    // Put the image into a rectangle as large as the original image
    inImage.drawInRect(CGRectMake(0, 0, inImage.size.width, inImage.size.height))

    // Create a point within the space that is as bit as the image
    var rect = CGRectMake(atPoint.x, atPoint.y, inImage.size.width, inImage.size.height)

    // Draw the text into an image
    drawText.drawInRect(rect, withAttributes: textFontAttributes)

    // Create a new image out of the images we have created
    var newImage = UIGraphicsGetImageFromCurrentImageContext()

    // End the context now that we have the image we need
    UIGraphicsEndImageContext()

    //Pass the image back up to the caller
    return newImage

}

Чтобы вызвать это, вы просто передаете изображение:

textToImage("000", inImage: UIImage(named:"thisImage.png")!, atPoint: CGPointMake(20, 20))

Следующие ссылки помогли мне понять это:

Swift - Рисование текста с помощью drawInRect: withAttributes:

Как написать текст на изображении в Objective-C (iOS)?

Первоначальной целью было создать динамическое изображение, которое я мог бы использовать, AnnotaionViewнапример, для указания цены в заданном месте на карте, и это отлично сработало. Надеюсь, это поможет кому-то, кто пытается сделать то же самое.

Для Swift 3:

 func textToImage(drawText text: NSString, inImage image: UIImage, atPoint point: CGPoint) -> UIImage {
    let textColor = UIColor.white
    let textFont = UIFont(name: "Helvetica Bold", size: 12)!

    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(image.size, false, scale)

    let textFontAttributes = [
        NSFontAttributeName: textFont,
        NSForegroundColorAttributeName: textColor,
        ] as [String : Any]
    image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))

    let rect = CGRect(origin: point, size: image.size)
    text.draw(in: rect, withAttributes: textFontAttributes)

    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
 }

Для Swift 4:

 func textToImage(drawText text: String, inImage image: UIImage, atPoint point: CGPoint) -> UIImage {
    let textColor = UIColor.white
    let textFont = UIFont(name: "Helvetica Bold", size: 12)!

    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(image.size, false, scale)

    let textFontAttributes = [
        NSAttributedStringKey.font: textFont,
        NSAttributedStringKey.foregroundColor: textColor,
        ] as [NSAttributedStringKey : Any]
    image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))

    let rect = CGRect(origin: point, size: image.size)
    text.draw(in: rect, withAttributes: textFontAttributes)

    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
 }

Для Swift 5:

func textToImage(drawText text: String, inImage image: UIImage, atPoint point: CGPoint) -> UIImage {
    let textColor = UIColor.white
    let textFont = UIFont(name: "Helvetica Bold", size: 12)!

    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(image.size, false, scale)

    let textFontAttributes = [
        NSAttributedString.Key.font: textFont,
        NSAttributedString.Key.foregroundColor: textColor,
        ] as [NSAttributedString.Key : Any]
    image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))

    let rect = CGRect(origin: point, size: image.size)
    text.draw(in: rect, withAttributes: textFontAttributes)

    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
}

My simple solution:

func generateImageWithText(text: String) -> UIImage? {
    let image = UIImage(named: "imageWithoutText")!

    let imageView = UIImageView(image: image)
    imageView.backgroundColor = UIColor.clear
    imageView.frame = CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height)

    let label = UILabel(frame: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
    label.backgroundColor = UIColor.clear
    label.textAlignment = .center
    label.textColor = UIColor.white
    label.text = text

    UIGraphicsBeginImageContextWithOptions(label.bounds.size, false, 0)
    imageView.layer.render(in: UIGraphicsGetCurrentContext()!)
    label.layer.render(in: UIGraphicsGetCurrentContext()!)
    let imageWithText = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return imageWithText
}

You can also do a CATextLayer.

    // 1
let textLayer = CATextLayer()
textLayer.frame = someView.bounds

// 2
let string = String(
  repeating: "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce auctor arcu quis velit congue dictum. ", 
  count: 20
)

textLayer.string = string

// 3
let fontName: CFStringRef = "Noteworthy-Light"
textLayer.font = CTFontCreateWithName(fontName, fontSize, nil)

// 4
textLayer.foregroundColor = UIColor.darkGray.cgColor
textLayer.isWrapped = true
textLayer.alignmentMode = kCAAlignmentLeft
textLayer.contentsScale = UIScreen.main.scale
someView.layer.addSublayer(textLayer)

https://www.raywenderlich.com/402-calayer-tutorial-for-ios-getting-started

I have created an extension for using it everywhere :

import Foundation
import UIKit
extension UIImage {

    class func createImageWithLabelOverlay(label: UILabel,imageSize: CGSize, image: UIImage) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(CGSize(width: imageSize.width, height: imageSize.height), false, 2.0)
        let currentView = UIView.init(frame: CGRect(x: 0, y: 0, width: imageSize.width, height: imageSize.height))
        let currentImage = UIImageView.init(image: image)
        currentImage.frame = CGRect(x: 0, y: 0, width: imageSize.width, height: imageSize.height)
        currentView.addSubview(currentImage)
        currentView.addSubview(label)
        currentView.layer.render(in: UIGraphicsGetCurrentContext()!)
        let img = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return img!
    }

}

Usage : Anywhere on your ViewController where you have the size and the label to add use it as follows -

let newImageWithOverlay = UIImage.createImageWithLabelOverlay(label: labelToAdd, imageSize: size, image: editedImage)

For swift 4:

func textToImage(drawText text: NSString, inImage image: UIImage, atPoint point: CGPoint) -> UIImage {


    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(image.size, false, scale)

    image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))

    let rect = CGRect(origin: point, size: image.size)

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



    let attrs = [NSAttributedStringKey.font: UIFont(name: "Helvetica Bold", size: 12)!,NSAttributedStringKey.foregroundColor : UIColor.white , NSAttributedStringKey.paragraphStyle: paragraphStyle]


    text.draw(with: rect, options: .usesLineFragmentOrigin, attributes: attrs, context: nil)



    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
}

I can't see anything in your initial question suggesting that this must be done exclusively in code - so why not simply add a UILabel in interface builder, and add constraints to give it the same length and width as your image, center it vertically and horizontally (or however you need it placed), delete the label text, set the text font, size, colour, etc. as needed (including ticking Autoshrink with whatever minimum size or scale you need), and ensure it's background is transparent.

Then just connect it to an IBOutlet, and set the text in code as needed (e.g. in viewWillAppear, or by using a ViewModel approach and setting it on initialisation of your view/viewcontroller).

I have tried this basic components. Hope it will work.

func imageWithText(image : UIImage, text : String) -> UIImage {

        let outerView = UIView(frame: CGRect(x: 0, y: 0, width: image.size.width / 2, height: image.size.height / 2))
        let imgView = UIImageView(frame: CGRect(x: 0, y: 0, width: outerView.frame.width, height: outerView.frame.height))
        imgView.image = image
        outerView.addSubview(imgView)

        let lbl = UILabel(frame: CGRect(x: 5, y: 5, width: outerView.frame.width, height: 200))
        lbl.font = UIFont(name: "HelveticaNeue-Bold", size: 70)
        lbl.text = text
        lbl.textAlignment = .left
        lbl.textColor = UIColor.blue

        outerView.addSubview(lbl)

        let renderer = UIGraphicsImageRenderer(size: outerView.bounds.size)
        let convertedImage = renderer.image { ctx in
            outerView.drawHierarchy(in: outerView.bounds, afterScreenUpdates: true)

        }
        return convertedImage
    }