Not the original commenter, but mitmproxy (https://mitmproxy.org/) can do this out-of-the-box for a single site with its reverse proxy:

    mitmdump --mode=reverse:https://news.ycombinator.com

And then visiting http://localhost:8080 will direct to the site.

There's also a nice (though under-documented) scripting interface, so you could probably write a script that does this for all sites in regular proxy mode. I found an example of this here, though I didn't test it: https://groups.google.com/forum/#!topic/mitmproxy/IAJ0-MHVC0...

back in the day I used RabbIT which handled both the https/http and the png problem but it looks like it hasn't been updated in years. It looks like squid can do the https problem (https://wiki.squid-cache.org/Features/HTTPS).

This actually doesn't looks as easy to do in 2020 as it was in 2009. I also had luck at chaining proxies that did different features as well so one would do a certain transformation and pass it off to another etc.

I've also done partial implementations just using php ... you can preg_replace most things and it more or less works.

But yes I had assumed things had gotten easier but apparently they've actually become more difficult.