What are some alternatives?
When comparing GIMP and Krita, you can also consider the following products
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
Paint.NET - Paint.NET is a free image and photo editing software.
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.