There is the DJVU format for this exact use case, but you’d need to convert them to, say, pdf for many use case. Its also a bit old and perhaps not maintained, soo…
HEIF and other modern video encoders (HEIF=H265) should fare a lot better than JPEG, though.
Did you give it to it?
It can be a pretty nice feature for using map-based apps in the browser.
I haven’t used such websites for a while and I don’t see Firefox in the recent users of the location API, even though I use Firefox Android all the time. (Info available in Android under Settings/Location.)