Add text to image in loop swift - ios

Question

I am adding text to an array of images using swift. Below is my code for the loop:
var holderClass = HolderClass()
var newImages = [UIImage]()
var counter = 0
for (index, oldImage) in holderClass.oldImages.enumerated(){
let newImage = drawTextAtLoaction(text: "testing", image: oldImage)
newImages[index] = newImage
counter+=1
if(counter == self.storyModule.getImageCount()){
completionHandler(newImages)
}
}
Here is the adding text function:
func drawTextAtLoaction(text: String, image: UIImage) -> 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: CGPoint(x: 0, y: 0), size: image.size)
text.draw(in: rect, withAttributes: textFontAttributes)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
if newImage != nil{
return newImage!
}else{
return image
}
}
Intuitively this loop should take constant storage, however, as shown by the following image it takes linear storage and causes memory errors with larger numbers of images.
How can I use constant memory for such an operation?
edit: I think that I may have oversimplified this a bit. The oldImages array is really an array of images inside an object. So the initialization of old images looks as so.
class HolderClass{
private var oldImages: [UIImage]!
init(){
oldImages = [UIImage(), UIImage()]
}
}
edit 2:
This is how the image data is loaded. The following code is in viewDidLoad.
var holderClass = HolderClass()
DispatchQueue.global(qos: .background).async {
var dataIntermediate = [StoryData]()
let dataRequest:NSFetchRequest<StoryData> = StoryData.fetchRequest()
do {
dataIntermediate = try self.managedObjectContext.fetch(dataRequest)
for storyData in dataIntermediate{
var retrievedImageArray = [UIImage]()
if let loadedImage = DocumentSaveManager.loadImageFromPath(imageId: Int(storyData.id)){
retrievedImageArray.append(loadedImage)
}
holderData.oldImages = retrievedImageArray
}
}catch{
print("Failed to load data \(error.localizedDescription)")
}
}
This is the DocumentSaveManager class.
static func documentDirectoryURL() -> URL {
let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
return documentsURL
}
static func saveInDocumentsDirectory(foldername:String, filename: String) -> URL {
let fileURL = documentDirectoryURL().appendingPathComponent(foldername).appendingPathComponent(filename)
return fileURL
}
static func loadImageFromPath(moduleId: Int, imageId: Int) -> UIImage? {
let path = saveInDocumentsDirectory(foldername: String(describing: moduleId), filename: String(describing: imageId)).path
let image = UIImage(contentsOfFile: path)
if image == nil {
return nil // Remember to alert user
}
return image
}