create Snapshot of entire SpreadsheetView (SpreadsheetView: https://github.com/kishikawakatsumi/SpreadsheetView)

Snapshotter.swift

class Snapshotter {
    static func createSnapshot(spreadsheetView: SpreadsheetView) -> UIImage? {
        guard let rootView = spreadsheetView.subviews[0] as? UIScrollView,
            let overlayView = spreadsheetView.subviews[1] as? UIScrollView else { return nil }
        
        let bounds = spreadsheetView.bounds
        let contentSize = overlayView.contentSize
        let contentOffset = rootView.contentOffset
        
        let numberOfColumns = Int(contentSize.width / bounds.width)
        let columnRemain = contentSize.width.truncatingRemainder(dividingBy: bounds.width)
        let numberOfPagesForColumn = numberOfColumns + (columnRemain > 0 ? 1 : 0)
        
        let numberOfRows = Int(contentSize.height / bounds.height)
        let rowRemain = contentSize.height.truncatingRemainder(dividingBy: bounds.height)
        let numberOfPagesForRow = numberOfRows + (rowRemain > 0 ? 1 : 0)
        
        rootView.contentOffset = .zero
        let lastColumn = numberOfPagesForColumn - 1
        let lastRow = numberOfPagesForRow - 1
        var elements = [Element]()
        for column in 0..<numberOfPagesForColumn {
            for row in 0..<numberOfPagesForRow {
                let offset: CGPoint
                if column == lastColumn && row == lastRow {
                    offset = CGPoint(x: contentSize.width - bounds.width,
                                     y: contentSize.height - bounds.height)
                } else if column == lastColumn {
                    offset = CGPoint(x: contentSize.width - bounds.width,
                                     y: bounds.height * CGFloat(row))
                } else if row == lastRow {
                    offset = CGPoint(x: bounds.width * CGFloat(column),
                                     y: contentSize.height - bounds.height)
                } else {
                    offset = CGPoint(x: bounds.width * CGFloat(column),
                                     y: bounds.height * CGFloat(row))
                }
                spreadsheetView.setContentOffset(offset, animated: false)
                guard let image = spreadsheetView.snapshot else { continue }
                let element = Element(rect: CGRect(origin: offset, size: bounds.size), image: image)
                elements.append(element)
            }
        }
        
        // ContentOffsetをもとに戻す
        spreadsheetView.setContentOffset(contentOffset, animated: false)
        
        let image = composeImage(size: contentSize,
                                 elements: elements)
        return image
    }
}

private extension Snapshotter {
    struct Element {
        let rect: CGRect
        let image: UIImage
    }
    
    static func composeImage(size: CGSize, elements: [Element]) -> UIImage? {
        defer {
            // end context
            UIGraphicsEndImageContext()
        }
        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
        
        // x座標が大きい方から描画されるように並び替える
        let sortedElements = elements.sorted { $0.rect.origin.x > $1.rect.origin.x }
        
        sortedElements.forEach { element in
            element.image.draw(in: element.rect)
        }
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

private extension UIView {
    var snapshot: UIImage? {
        defer {
            // end context
            UIGraphicsEndImageContext()
        }
        let size = bounds.size
        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        layer.render(in: context)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        return image
    }
}

It's a code I wrote a long time ago, so I can't answer it immediately.
I'm sorry.
I will check when I have time.