Stitch/Composite multiple images vertically and save as one image (iOS, objective-c)

Question

I need help writing an objective-c function that will take in an array of UIImages/PNGs, and return/save one tall image of all the images stitched together in order vertical

Answer 1

Swift 4

extension Array where Element: UIImage {
    func stitchImages(isVertical: Bool) -> UIImage {

        let maxWidth = self.compactMap { $0.size.width }.max()
        let maxHeight = self.compactMap { $0.size.height }.max()

        let maxSize = CGSize(width: maxWidth ?? 0, height: maxHeight ?? 0)
        let totalSize = isVertical ?
            CGSize(width: maxSize.width, height: maxSize.height * (CGFloat)(self.count))
            : CGSize(width: maxSize.width  * (CGFloat)(self.count), height:  maxSize.height)
        let renderer = UIGraphicsImageRenderer(size: totalSize)

        return renderer.image { (context) in
            for (index, image) in self.enumerated() {
                let rect = AVMakeRect(aspectRatio: image.size, insideRect: isVertical ?
                    CGRect(x: 0, y: maxSize.height * CGFloat(index), width: maxSize.width, height: maxSize.height) :
                    CGRect(x: maxSize.width * CGFloat(index), y: 0, width: maxSize.width, height: maxSize.height))
                image.draw(in: rect)
            }
        }
    }
}