Image rotation of MKOverlay

Hi, I'm making the map app to insert a custom MKOverlay. I specified the image in Asset catalog as an image of MKOVerlay. However, the overlay image in the map was reversed vertically as shown in the **** figure.

https://share.icloud.com/photos/0ofoyXKRlJnN_1phqRP79WBrw

I confirmed that the instance of UIImage to be rendered in a map had been created by specifying a correct asset name. The following is a part of the class inherits MKOverlayRenderer. I cannot understand the rotation of the image. Please teach me the reason for this phenomenon.

     init(overlay: MKOVerlayWindIcon){
        pOverlay = overlay

        super.init(overlay: pOverlay)

        if let tmpImg = GenerateImage(data: pOverlay.data){
            pImageToRender = tmpImg
        }else{
            os_log(.error, "Failed to generage icon image")
        }
        
    }
    
    override func draw(_ mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {
        let rectToRender : CGRect = calcCGRect(for: zoomScale)
        if let imageToReder = pImageToRender?.cgImage{
            context.draw(imageToReder, in: rectToRender)
        }else{
            os_log("Invalid image was passed", log: OSLog.default, type: .debug)
        }
    }
    
    func GenerateImage(data :WindData) -> UIImage?{
        let assetName = "WI_337.5"
        return UIImage.init(named: assetName)
    }