WatchOS5 - what is the "Graphic rectangular" complication image size?

I'm looking at this list of complication images for WatchOS5 by Apple, it mentions template for the graphic rectangular complication on 44mm watch being 342px × 108px (171pt × 54pt @2x)

I tried sending 342x108 image, and it is too large - it appears the default scaling mode is "center". I also tried 171x54 and it is too small and blurry - other images I display on apple watch are much more crisp

What is the correct size /scale for the Graphic Rectangular WatchOS5 complication ? Is it possible for the app or watchkit/exstension to query the rectangle available for complication?

    var image: UIImage = UIImage()

    let fileManager = FileManager.default
    do {
        let fileURL = try //...URL of complication file

        let data = try Data(contentsOf: fileURL)
        image = UIImage(data: data)

    } catch {
        image =  UIImage(named: "placeholder") ?? UIImage()
    }

    let textProvider = CLKSimpleTextProvider(text: SessionDelegater.title)
    template.textProvider = textProvider
    template.imageProvider = CLKFullColorImageProvider(fullColorImage: image)

Partial workaround - manually recreate image from CGImage and assign scale factor of 2:

        var image: UIImage = UIImage()
        do {
            let fileURL = try FileManager.fileURL("complication")

            let data = try Data(contentsOf: fileURL)
            image = UIImage(data: data) ?? UIImage()
            if let cgImage = image.cgImage {
                  image =  UIImage(cgImage: cgImage, scale: 2, orientation: image.imageOrientation)
            }

        } catch {
            print(error)

            image =  UIImage(named: "image1") ?? UIImage()
        }