Image editors for Mac as of late 2016

[special_ed]

Sorry if this is a relatively beaten to death topic. I've already used the search function.

I'm looking for a new image editor to use for editing pixel art and sprite sheets. I'm running OS X Sierra on a Retina MacBook Pro (2.3 GHz quad core, 8 GB Ram, GeForce GT 650m 1GB). I've already ruled out the following commonly recommended editors:

Photoshop CC - I consider this the best image editor, all things considered. However, I'm broke, unemployed, and not willing to pay for it. I'm also not willing to install pirated Adobe products.

GIMP 2.8 - Before I was an art student and in love with Mac + Adobe, I was a computer science major who exclusively used Linux. Over this period of time, I got acclimated to GIMP and considered it a pretty good, free, and open source alternative to Photoshop. As of 2016, however, it's borderline useless. Most of the functionality I want is theoretically there, but it suffers from performance problems, bugs, and crashes. Earlier today, it crashed about a dozen times when I was editing very, very small sprite sheets and I've finally had enough of it.

Krita - This isn't a terrible alternative to GIMP. It doesn't suffer from as many problems on my system, but they're still there. The interface is also not as intuitive as I'd like it to be. I spend way too much time just learning how to use it.

What free image editors do you recommend for OS X? If they're geared towards pixel art that would be best.

My needs at the moment aren't terribly complex:

#1 Draw/erase pixels of various sizes. The tools in many editors default to "fuzzy" or "dynamic" behavior that can be annoying to disable. Managing transparency can get annoying in some cases, so it would help if it defaulted to transparent backgrounds and erasing to transparency.

#2 Resizing the canvas/image. It seems simple enough, but GIMP would frequently crash. 

#3 Selecting rectangular areas and easily cutting/copying/pasting/rotating them within a sheet.

#4 Configurable grids. "Snap to grid" behavior for drawing/erasing/selecting. If this isn't present, then #1 and #3 are a pain.

#5 Robust color selection. Pick colors from images/area of screen (even in other applications). Save color history. Save palette of colors. GIMP was problematic here.

 

[mattstyles]

http://pyxeledit.com/ not free, but cheap, not sure its still under active development (I've got used to constant updates and stuff over the last couple of years) but its got a really nice tight sphere of influence so functionally its good, if what you need is what it does. I don't use it often, but its pretty clean and simple for pixelling.

[PixelPicoSean]

Aseprite of course, it's awesome pixel art tool meets all your needs.

[ericjbasti]

https://affinity.serif.com/en-us/photo/

and you can download a free trial all the way at the bottom.