UIGraphicsImageRenderer used in a loop ends with memory issue [duplicate] - ios

Question

This question already has answers here:
Swift5 MacOS ImageResize memory issue
(2 answers)
Closed last year.
I have a simple function like this:
let filteredImages = //array of images
let numbersArray = //array of array of numbers for ex [[1, 2], [2, 3]], total number of elements is 57
for (index, numbers) in numbersArray.enumerated() {
print(">>>>1 INDEX: \(index)")
if let cardimage = Box.card(for: filteredImages, numbers: numbers) {
//nothing here for now
}
}
class Box {
class func card(for images: [UIImage], numbers: [Int]) -> CardImage? {
var filteredImages = [UIImage]()
for number in numbers {
guard images.count > number - 1 else {
return nil
}
filteredImages.append(images[number - 1])
}
if filteredImages.count < 8 {
return nil
}
let creator = ImageCreator(radius: 500, backgroundColor: UIColor.athensGray)
return creator.card(from: filteredImages)
}
}
class ImageCreator {
private let radius: CGFloat
private let backgroundColor: UIColor
private let sets: [Set] //Array of predefined objects of my type Set, some numbers like x, y, width, height, radius
init(radius: CGFloat, backgroundColor: UIColor) {
self.radius = radius
self.backgroundColor = backgroundColor
}
func card(from images: [UIImage]) -> CardImage {
let renderer = UIGraphicsImageRenderer(size: CGSize(width: radius, height: radius))
var coordinates = [ImageCoordinate]()
let image = renderer.image { [weak self] context in
let size = renderer.format.bounds.size
self?.backgroundColor.setFill()
context.cgContext.fillEllipse(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let set = sets.random
for (index, image) in images.enumerated() {
if let positions = set?.positions[index], let cgimage = image.flippedVertically?.cgImage {
context.cgContext.translateBy(x: CGFloat(positions.x), y: CGFloat(positions.y))
context.cgContext.rotate(by: CGFloat(positions.r))
context.cgContext.translateBy(x: CGFloat(-positions.w/2), y: CGFloat(-positions.h/2))
let width = CGFloat(positions.w)
let height = CGFloat(positions.h)
var newWidth: CGFloat = 0
var newHeight: CGFloat = 0
let imageWidth = image.size.width
let imageHeight = image.size.height
let ratio = imageWidth / imageHeight
if ratio > 1 {
newWidth = CGFloat(width)
newHeight = newWidth / imageWidth * imageHeight
} else {
newHeight = CGFloat(height)
newWidth = newHeight / imageHeight * imageWidth
}
context.cgContext.translateBy(x: CGFloat((width - newWidth) / 2), y: CGFloat((height - newHeight) / 2))
context.cgContext.draw(cgimage, in: CGRect(x: 0, y: 0, width: newWidth, height: newHeight))
context.cgContext.translateBy(x: CGFloat(-(width - newWidth) / 2), y: CGFloat(-(height - newHeight) / 2))
context.cgContext.translateBy(x: CGFloat(positions.w/2), y: CGFloat(positions.h/2))
context.cgContext.rotate(by: CGFloat(-positions.r))
context.cgContext.translateBy(x: CGFloat(-positions.x), y: CGFloat(-positions.y))
coordinates.append(ImageCoordinate(x: positions.x, y: positions.y, w: Double(newWidth), h: Double(newHeight), r: positions.r))
}
}
}
return CardImage(image: image, coordinates: coordinates)
}
}
I think it is not complicated as much because I do here a lot of staff with delivered set of images (always 8 images), but when I do it with a loop for i in 1...57 it ends up with memory issue (app is closed after ~31 iterations). Why?
How can I avoid that? Is there a way to fix that problem?

Answer 1

I suspect the problem you are encountering is caused by accumulating too many temporary (autorelease) objects (in this case the CGImages in the card method) in the loop that is rendering your cards.
I would try adding an autoreleasepool around the rendering of the card images.
for (index, numbers) in numbersArray.enumerated() {
autoreleasepool {
print(">>>>1 INDEX: \(index)")
if let cardimage = Box.card(for: filteredImages, numbers: numbers) {
//nothing here for now
}
}
}