Sorry if this is the wrong place for this, I don't see where feature requests would go, neither could I find an email.
Since this plugin is super useful for theme developers, why not make it so that settings can be imported, or pre-set for a theme? Meaning, make it so I can hard code in the options in the settings > responsive images area in my theme. (I use a plugin auto installer on theme installation, TGMPA to be exact, and I might make my own.)
Maybe a warning that can be put up by theme developers to the user not to change things unless the user knows what they're doing, and making the defaults button set it back to the theme's pre-set settings?
It would be a great feature IMO, and it would be even more complete than it already is.
(Also, does this work locally, meaning would it work on localhost on my windows computer?)