Digitally Inking Sketches with Inkscape and GIMP – Part 1

The Technique

First, we’re going to outline our sketch with shapes and lines in Inkscape. Then, in Part 2, we’re going to import those shapes and lines as paths in GIMP, and use GIMP to do our coloring, shading, and effects.

So why use this vectoring technique? We could just as easily open this thing up in GIMP, trace over it with the pencil tool, and be done, right? Well, yes. In fact, it’d be quicker for us to do it that way. But doing it this way, we get a lot more flexibility at the cost of a little more work.

To understand why this technique is different than tracing in GIMP, you have to understand that there are two types of images in the digital world: raster images and vector images.

Raster images are made up of pixels. These are your PNGs, JPEGs, and GIFs–the things you generally create in Photoshop or GIMP. Because they’re based on pixels, they’re fixed to a certain size, and they don’t really scale up (or sometimes down) so well. But they’re really good for detailed, free-form graphics, like some of the blur effects we’ll want to use for shading. We do want our final product to be a raster graphic, but we want a little more freedom when we’re actually outlining our scan.

Vector images are made up of lines and shapes. Photoshop and GIMP support this to varying degrees as paths, but if you want to really work with vector images, you need to use Illustrator or Inkscape. The advantage to vector graphics is that they scale up and down cleanly. Since they’re a series of lines and shapes, they can be transformed mathematically with no loss of detail (as compared to raster images, where pixels must be generated or hidden to scale the image). But because of this, they’re mainly for simpler images that have large, solid color areas.

What we’re doing is combining the best of both worlds: we’ll store our basic outline as a vector image, then we’ll render it as a raster image for the purposes of shading, coloring, and effects.

Starting out with vector graphics gives us two major advantages. One, they make it easier to create nice smooth shapes than if we manually traced over our sketch (especially if you’re using a mouse). If you screw up in drawing a line, you don’t have to completely re-draw it; you just drag its handles around until it fits.

Two, they give us a lot of flexibility. Say we want to scale our image up to the size of a desktop wallpaper (as I eventually want to do with the Maitre d’). Or maybe we don’t like the original brush size or color we used to trace the image. All we have to do is redo our stroking and filling in GIMP–no retracing required. (Of course, this isn’t free–it’s still a lot of work because you have to stroke and fill shape-by-shape, although that’s certainly not as tedious as redrawing it entirely. And the more shapes/paths your image contains, the more work it is.)

Incidentally, this is one of the ways things like anime or cartoon wallpaper is made. Because of the way most anime and cartoons are colored and shaded, the technique lends itself well to vector graphics. So if you’re interested in doing that, just take this technique and use it to trace over a screen capture or scan rather than a sketch of your own. This gets rid of any extra artifacts in the scan or screen capture, plus it allows you to scale the image up from the original size to fit your desktop resolution.

That said, just why are we using Inkscape anyway? GIMP supports paths which are basically the same thing; doesn’t using Inkscape just add an extra layer of complexity?

Yes, it does. It essentially means that you’re going to have to build your image twice–once as lines and curves in Inkscape, and then again as stroked-and-filled shapes in GIMP. But Inkscape’s user interface for working with lines and shapes is much easier to use and much more forgiving than GIMP’s paths. That’s not knocking GIMP–it’s very good for what it is. But Inkscape is specifically built for vector images, and so does it much better than the all-purpose GIMP.

So, with that covered, let’s see how this process actually works.