FREE The Gimp Team, gimp.org
Gimp, an open-source bitmap image editor, has been around for as long as OS X. If your Mac runs Mountain Lion, Mavericks, or Yosemite, you can install it as a native application, otherwise you’ll have to
install X11 first (http://apple.co/1ML4qBk).
While the app’s interface is very different
to Photoshop, many tools found in Adobe’s heavyweight image editor are also provided here. There’s the lasso and magic wand for selection, a pen tool for drawing Bézier paths, a paintbrush, and a clone stamp. You can build up your images on multiple layers, too.
Some tools can be hard to find if you’re used to something Photoshop – the Levels dialog is in the Color menu, for example. The good news is that the interface is customisable, so you can set it up just how you like, and have different environments for different tasks.
The app includes a full set of painting tools, including Brush, Pencil, Airbrush, and Clone. It features a powerful gradient editor and a blend tool, and you can import custom brushes and patterns. There’s full support for multiple layers and channels, including alpha channels, and the number of undo operations you can perform are limited only by the amount of disk space that’s available.
For selecting pixels, familiar rectangle, rounded rectangle, and lasso tools have you covered, as well as advanced path tools for creating Bézier curve and polygonal selections. Transformation tools include rotate, scale, shear and flip, and there are tools to fix lens distortion, barrel distortion and vignetting.
Perhaps Gimp’s most important feature is that it’s extensible. Anyone can create plug-ins for it and share them – over 100 are already available (http://registry.gimp.org). Plug-ins can be written using the Scheme, Python and Perl languages, and this scripting language support allows Gimp to be automated too.
Gimp isn’t perfect, of course. Its Text tool is in need of much improvement, and there are none of the 3D tools available in Photoshop to be found here. Nor does it support anything
like Photoshop’s non-destructive Adjustment
Layers for easy experimentation with colour
changes. Other missing features are taken care of by third party plug-ins, such as support for the CMYK colour space, which is available in Separate+ (http://bit.ly/mf289separate).
Gimp is not a complete replacement for Photoshop, but it provides so many features found in Adobe’s venerable bitmap editor that, for most purposes, it’s a perfectly usable alternative. Thorough documentation and tutorials make it relatively easy to get started, and a large development community and user base mean Gimp’s constantly evolving.
Although Gimp’s interface is different to Adobe Photoshop, its layout – with tools and their options on the left and other palettes on the right – is familiar and eases you into free image editing.
Gimp’s already extensive capabilities can be taken further by downloading plug-ins from a huge online repository.