Pinta is an open-source image editor designed for Mac. The application looks a bit like the Paint utility that's installed by default on Windows PCs. You will have access to various image editing options, the ability to resize pictures without losing their quality, and the option to convert photos to other formats.
This program is perfect for little kids to doodle freely. It can also be used by grown-ups to create multi-layered photos and make adjustments to their digital photographs.
An advantage is that the application gives you access to multiple visual effects. Also, you can undo as many image alterations as you like.
Unfortunately, the program supports a limited amount of image formats. You cannot import or export GIF, PSD or Exif files. Thus, you can find other open-source or free image editors that provide you with a lot more features and work with a wider variety of photo formats.
For these reasons, I don't think it's worth installing this utility on your Mac. Still, this program is free of charge and you don't have nothing to lose if you decide to give it a shot. So, it's up to you to decide whether you should install this image editor on your Mac or not.