Pixelmator vs GrafX2

Pixelmator's interface is pleasant to look at, easy to use and specifically optimized for OS X users, making it very intuitive for long-time Mac users.

Not only does Piexelmator provide easy to use tools that you should expect in any image editor, it also has rare tools such as layer styles, liquify tools and OS X optimized, fast image manipulation engine among others.

Layer styles allow non-destructively applying effects to a layer.

Dozens of visual effects available, easily discovered from the visual Effects Browser, broken into categories. Effects have interactive dialogs and live preview.

Pixelmator can be used across any number of monitors.

Gives you common image editing capabilities almost instantly.

Pixelmator's image engine is specifically optimized for use with Macs, providing one the best performance results available on OS X.

Pixelmator costs just $30 on the App Store. Additionally, it often comes bundled with other software that you might also find useful bringing the price down.

GrafX2 is scriptable using the Lua language, which can be used to automate tasks and add new functionality to it. The script library features advanced color reduction and enhancement tools, palette analysis, and much more.

GrafX2 supports many file formats, including the popular gif and png, but also importing and exporting from deluxe paint, degas elite, and various other editors using custom formats.

GrafX2 is totally free to use, copy, and modify. It's available on Windows, Linux, Mac OS X, Haiku, AROS, MorphOS, SkyOS, Syllable, Mint, and a few more systems. Basically anything is supported by the SDL library.

GraphX2 being based on older 256 bitmap software has inherited some tricks that modern pixel editors do not have . One of them being the ability to cycle color palette and produce animations and effects with it.

You can create gradients from one color to another, work in either RGB or HSL color space, save and load palettes, sort and organize palettes, and even work on "color cycling" images.

The program has a basic support for animation using frames in newer versions. Graphics can be cloned and copied between frames and changed slightly.
See here how to animate with GrapfX2 https://www.youtube.com/watch?v=Gnq6zBZOqoM

Theme UI style can easily be changed from settings including buttons and colors.

The program is able to enforce the pixel constraints of old machines (C64, ZX Spectrum, Apple II, Game Boy Color, etc.)
For example, in ZX Spectrum mode, only 2 different colors can be used in a 8x8 pixel block.