G'MIC: the world’s most flexible image processor?

G’MIC (GREYC’s Magic for Image Computing) is an exceptionally powerful image processing tool for the command line (or via GIMP, if you install it via a plugin). It’s aimed very much at experts, but has features which can be used by just about everyone.

At its simplest, you might use the program to view a series of images (gmic pic1.jpg pic2.jpg pic3.jpg) or convert an image from one format to another (gmic ThisPicture.png Output.png).

G’MIC also supports an array of image filters and processing commands. You’re able to mirror, crop, rotate and resize images, blur and sharpen them, remove red-eye, use various warps and deformations (fisheye, sphere, kaleidoscope, more), apply paint and drawing effects, create animations, and add captions, borders and drop shadows.

And that’s just a tiny fraction of what’s on offer.

These effects are sometimes very easy to use. Applying a sepia-type "old photo" look just requires the command like this:

gmic image.jpg -old_photo

But G’MIC also provides astonishing flexibility, for people who need it. You don’t just have a basic "-blur", for example: you’re able to select a filter type, a border setting, various blur types (angular, radial, linear, selective), a direction (x/ xy/ xyz/ y/ z) and more.

Still not enough? Pipeline support means commands can be combined on a single line for better effect. Once you know what you’re doing you can even extend the program with your own filters and custom commands.

The results can be amazing. G’MIC isn’t just another me-too image tweaker, it’s easily strong enough for professional use, and you don’t have to take our word for it: just browse through Flickr’s G’MIC group pool and see for yourself.

But even this is just the start. G’MIC can also work with videos (via FFMPEG), plot 2 or 3D functions, create 3D logos and models, display a filtered webcam stream, and more. Here’s a sample command to generate a 3D vase, for instance:

gmic -md3d 4 -isosurface3d “‘x^2+2*abs(y/2)*sin(2*y)^2+z^2-3′,0″ -sphere3d 1.5  –3d[-1] 0,5 -plane3d 15,15 -r3d[-1] 1,0,0,90 -c3d[-1] -+3d[-1] 0,3.2  -col3d[-1] 180,150,255 -col3d[-2] 128,255,0 -col3d[-3] 255,128,0 -+3d

This can all seem a little intimidating, but keep in mind that G’MIC can be used as a GIMP plugin for easier ad-hoc use (just unzip its files to your GIMP plug-in directory, or see here).

Or, if you’re going to try the command line version, the program has some built-in demos to show you what’s possible. Enter gmic -demo and prepare to be impressed.