Advanced Image Processing with GIMP and G’MIC

If you’re a digital artist or designer, you’ve no doubt heard of the GNU Image Manipulation Program (GIMP), often referred to as the preeminent open-source alternative to Photoshop. But did you know that you can extend GIMP’s features dramatically with a plugin called G’MIC?

G’MIC stands for GREYC’s Magic Image Converter, but it does a lot more than just convert images. It provides many pre-defined filters and effects for your images along with the capability of writing your own filters in the G’MIC scripting language. G’MIC even does 3D imaging! Its authors refer to it as “a serious (and friendly) competitor of the ImageMagick or GraphicsMagick software suites.“. Today I’m going to show you just a few of the things you can accomplish with GIMP and G’MIC together.

While there is a standalone program for G’MIC that can be used from the command line, this article is going to focus on the GIMP plugin.

First you need GIMP itself, which you can get on the GIMP site for several different platforms.

You can then download the G’MIC plugin for Linux, Mac OS X, or Windows.

The Windows download includes an installer, but if you’re on Linux or OS X, you must install the plugin manually. This just means extracting the ZIP file into your GIMP plugins directory. This is usually located at “$HOME/.gimp-2.x/plug-ins/”.

From within GIMP, you’ll find G’MIC at the bottom of the “Filters” menu.

gmic-menu

When you open it, you’ll see something like this:

gmic-interface

Found G’MIC? Great! Let’s see what we can do with it. The rest of this article will be divided into sections based on G’MIC’s own filter categories so that you can easily find any of the filters I mention.

Dithering

Dithering is a neat little effect that creates color and shading with concentrated spots, much like half-toning. I particularly enjoy dithering comic art to make it have even more of a comic look.

gmic-dither

Ink wash

The ink wash filter is a lovely way to make a photograph look like a handcrafted work of art.

gmic-inkwash

Old photograph

Who needs all those “vintage” Instagram filters when one can make a much more convincing old photograph in G’MIC?

gmic-oldphoto

Lylejk’s painting

This one can accomplish a range of effects if you play with the parameters, which include iterations, radius, and canvas size. Personally, I like the Van Gogh look. And if you’re curious, “Lylejk” appears to be the digital artist Lyle J. Kroll.

gmic-lylejk

G’MIC has several presets for arrays and frames. I’ll just show you one example here.

Array (mirrored)

gmic-array-mirrored

Distance transform

Care for insta-microbes? Just apply the distance transform filter to your image, and you’ll get them. Note that we’ve reduced the size of the example image for the Web; the original is actually of a much smoother appearance.

gmic-distance-transform

By default, the metric is set to Euclidean; change it to Chebyshev or Manhattan for a more geometric effect:

gmic-distance-transform-manhattan

Skeleton

The skeleton filter is a good one to use when touching up the back-cover author photo for your next self-published sci-fi novel. It turns spots of color into webs of lines.

gmic-skeleton

Shade bobs

Shade bobs accumulate large splotches of color on curved lines to generate an abstract image. Be sure to use this filter on the cover art for your band’s next psychedelic rock album.

gmic-shade-bobs

Quick copyright

Taking a break from the wild abstractness of the previous filters I showed you, here’s one that’s simply practical. The parameters for the quick copyright filter let you choose various aspects of your copyright’s appearance, including font color, size, and placement. This example shows the copyright in the lower right of the image:

gmic-quick-copyright

Edges on fire

“Edges on fire” finds the edges in your image and adds a flame effect to them, with the brightness of the flame depending on the brightness of each part of the image.

gmic-edges-on-fire

Custom code

This filter is a placeholder for inputting your own G’MIC script. You can edit the code straight from the G’MIC interface using the text box provided.

gmic-custom-code

My system shows that there are 276 different G’MIC filters available. Unfortunately, that’s too many to fit in this article, but it should give you a lot to look forward to when you install this plugin. You could spend days exploring all of the strange, practical, impractical, sometimes totally random, often beautiful effects that the GIMP and G’MIC can accomplish.

For those who are interested, you can also get the standalone program here on Sourceforge.