Save image to file on macOS using swift, answers found from SO

saveImage.swift

// plain write to image
@discardableResult func writeCGImage(_ image: CGImage, to destinationURL: URL) -> Bool {
    guard let destination = CGImageDestinationCreateWithURL(destinationURL as CFURL, kUTTypePNG, 1, nil) else { return false }
    CGImageDestinationAddImage(destination, image, nil)
    return CGImageDestinationFinalize(destination)
}


// There's a panel, save image png

@IBAction func saveImage(sender: Any){
    let savePanel = NSSavePanel()
    savePanel.canCreateDirectories = true
    savePanel.showsTagField = false
    savePanel.nameFieldStringValue = "screenshot.png"
    savePanel.level = Int(CGWindowLevelForKey(.modalPanelWindow))
    savePanel.begin { (result) in
        if result == NSFileHandlingPanelOKButton {
            guard let url = savePanel.url else { return }

            let bitmapRep = NSBitmapImageRep(cgImage: self.ikimageView.image().takeUnretainedValue())
            let data = bitmapRep.representation(using: .PNG, properties: [:])
            do {
                try data?.write(to: url, options: .atomicWrite)
            } catch {
                print(error.localizedDescription)
            }
        }
    }
}

// A more detailed, save image using IKImageView

@IBAction func saveImage(sender: AnyObject) {

    let savePanel = NSSavePanel()
    saveOptions = IKSaveOptions.init(imageProperties: [:], imageUTType: kUTTypePNG as String!)

    saveOptions.addAccessoryView(to: savePanel)
    savePanel.canSelectHiddenExtension = true
    guard let window = self.view.window else { return }
//        let fileName = window.representedURL?.lastPathComponent ?? "Untitled"
//        savePanel.nameFieldStringValue = fileName

    savePanel.beginSheetModal(for: window) { (result) in
        if result == NSFileHandlingPanelOKButton {
            self.savePanelDidEnd(sheet: savePanel,returnCode: result)
        }
    }
}


func savePanelDidEnd(sheet: NSSavePanel, returnCode: Int) {
    if returnCode == NSModalResponseOK {
        let newUTType = saveOptions.imageUTType
        let iamge = imageView.image().takeUnretainedValue()
        let url = sheet.url

        if let dest = CGImageDestinationCreateWithURL(url! as CFURL, newUTType! as CFString, 1, nil) {
            CGImageDestinationAddImage(dest, iamge, nil)
            CGImageDestinationFinalize(dest)
        } else {
            print("save Image to Path - no image")
        }
    }
}