November 2005

Creating Simple Backgrounds with the Gimp

Sometimes finding that perfect desktop background can actually end up taking a lot of time. Making one might be a better approach. In this article, the basics of building nice looking background images from a simple colored one with a pattern to multiple sourced bump mapped ones is discussed. The tool used is the GNU Image Manipulation Program also known as the GIMP.

A Basic Colored Plasma Pattern

Using the GIMPs prebuilt plasma plugin, a pretty nice background can be made. First, start the GIMP and select the size wanted for the image, 1024x768 for example. Next, from the image menu pick Filters -> Render -> Clouds -> Plasma...:

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The New Seed and Turbulence can be fiddled with to find a preferable pattern. For example, one color scheme overall will be used, however, the original colors can be used or modified by selecting Layer -> Colors and Hue Saturation or Color Balance. The following used Layer -> Colors -> Colorize:

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Initially the image will turn one color, usually a deep cyan color. The controls allow for altering it to other colors. That done, the first image has been created:

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So, a basic plasma background is pretty easy. A good time-hole of course would be playing with all of the different patterns and coloring, but for the next section, the same image will be used in conjunction with another to create a bumpmapped image.

A Simple Full Bump Map

An image can actually be bumpmapped without using any other images. Filter -> Map -> Bump Map:

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By playing around with the settings, most notably the depth and type (specified at the top with Linear etc.) a more or less even spread of raised bumps can be created. A ruddier surface might make for a more interesting pattern. An image from Rasterman's images:

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It is worth noting that the color of the bump source has no effect on the color of the original. Although they are both close to cyan, it is just coincidence.

To use the image, simply open it up in the GIMP, select the previous recolored plasma image, then go to Filter -> Map -> Bump Map, the rock image can now be selected as the source for the map:

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Another note here, the bump map source must be equal to or larger than the image it is being used in, otherwise, it will only map into the area defined by the X & Y axis area - which can be used for creating three dimensional watermarks (say for instance - a logo).

The result:

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That background is quite nice, and of course a variety of them could be made in different colors or using some of the more potent theming engines out there the color can be merged. Now a look at collaging bump maps.

Using a Collaged Bump Source Image

The final part of the article is about collaging source images into one large bump map source. The goal is a sort of three staged map, one sort of flat but textured image, one image with some sort of rocky pattern and one image in a clear pattern - luckily three that matched (respectively) were found:

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First, a new empty image needs to be created using the same size as the original plasma image (1024x768 - you of course can use whatever you like). Next, each of the bump source images needs to be resized then copied into the blank image. The bump sources can be scaled by selecting Image -> Scale Image. Next, the images can be copied and pasted into the empty image by right clicking, selecting Copy and then Paste Into at the destination. Now the hard part, figuring out what scale and how to pattern them can be difficult. Here are the results that ended up being used:

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The collage looks crude - and it is - but once it is used as a bump map source - the results are not so bad. Note the sharpnes which can be altered using Filters -> Blur, however, when used as a bump source there is some blurring that happens anyhow.

The process for using the collage as the source is the same. Open the original plasma image, then the collage, go back to the plasma image. Go to Filter -> Map -> Bump Map, the collage will now show up as a possible source:

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And the results:

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The article only touched a little bit about how to create one's own bump mapped or just plain background. With a little time and poking around, anyone with GIMP installed can enhance their desktop experience by creating a background that they want.