Hi awe, the image you have pasted above is rendered in the browser by the Bootstrap skin, using apache eCharts. Home of the skin:
https://github.com/brewster76/fuzzy-archerThe skin does not provide image generation for gauges and live charts in a way, that a static image is produced. The static image you linked above is produced in a completeley different way by weewx in the backend.
As far as I know, the eCharts library provides this, but the skin doesn't provide this functionality and it will not provide it in the future. The reason is that the gauges are only rendered in the browser, but not in the weewx backend.