Creating grunge brushes from an image

This is the most realistic-looking technique for grunge effects and is used extensively by Photoshop users. The essence of this technique in Photoshop is to open a picture and then make the contrast extreme - the result is often a random collection of black splotches on a white background that can be turned directly into a brush. In Inkscape we will achieve the same result using the Trace Bitmap function.

First, find a picture that has an even distribution of visual artefacts - a picture without a central subject. An ideal picture for our needs would be a background, or a pattern, picture. I used the mud picture for this tutorial because it is visually even. This picture comes from Mayang's Free Texture Library

Import the picture by going to [File -> Import] and selecting your picture. Then select the picture and go to [Path -> Trace Bitmap]. This tool takes a picture and creates a path from it. You can trace the edgest of objects in the picture, select coloured areas or bright areas, with the end result being a path that mimics the picture. Tweak the parameters and click on the Preview button to see what your final path will look like. Your goal is to create a path that looks like random black splotches.

After you see the kind of grunge path that we are looking for in the preview window, click OK and wait until the Stop button becomes grayed out. At this point the path is generated, close the window and drag the path away from the image (on top of which it will be positioned). After removing the strokes and adding a background this is what your grunge should look like:

This grunge brush looks much more realistic than the others, because the other two methods involve a non-random process in their creation. This method uses a very random source for the paths - nature. After setting the background to white and after a little tweaking, the illustration will look like so: