Now that Picasa is end-of-life, I would like suggestions about an alternative photo editor that is amateur-friendly. I am not a professional photographer. I am a programmer. But I do like to perform some quick enhancements on the photographs (like altering brightness, shadows, etc.). Is there a good free alternative (free as in free speech or free as in free beer)? If it works on all three of Mac, Linux and Windows, it's a bonus!
Gimp. Darktable. Learning to do simple things in either is probably a matter of a few hours but only one time. Then either is as fast as anything else. Yes, 'a few hours' sounds like a lot of time, but I have often found myself spending many hours on Google chasing software that does not exist.
Philosophically, the user spending a few hours learning Free software does not seem entirely disproportionate to the thousands of hours developers have spent developing it. Picasa was closed source because it was written to make money.
Not free but rather cheap (around 30€), but you should look at the Affinity suite (Photo in your case, and Design if you are at some point interested in vector drawing).
I made the exact same research a couple of years ago: I couldn’t afford Adobe’s products and wasn’t feeling Pro enough to use Photoshop nor Illustrator.
It’s snappy, easy to use and has lots of features for me not to feel constrained whenever I use it.
Philosophically, the user spending a few hours learning Free software does not seem entirely disproportionate to the thousands of hours developers have spent developing it. Picasa was closed source because it was written to make money.