'This will generate the new cover image from the cover in the library. It is a wrapper
for save_cover_data_to to allow it to be overriden in a subclass. For this reason,
options are passed in that are not used by this implementation.
:param cover_data:    original cover data
:param resize_to:     Size to resize the cover to (width, height). None means do not resize.
:param kobo_size:     Size of the cover image on the device.
:param upload_grayscale: boolean True if driver configured to send grayscale thumbnails
Passed to allow ability to decide to quantize to 16-col grayscale
at calibre end
:param keep_cover_aspect: bookean - True if the aspect ratio of the cover in the library is to be kept.
:param is_full_size:  True if this is the kobo_size is for the full size cover image
Passed to allow ability to process screensaver differently
to smaller thumbnails'

def _create_cover_data(self, cover_data, resize_to, kobo_size, upload_grayscale=False, keep_cover_aspect=False, is_full_size=False):

    from calibre.utils.img import save_cover_data_to
    data = save_cover_data_to(cover_data, grayscale=upload_grayscale, resize_to=resize_to)
    return data
