Filter is a name used in GIMP to describe a variety of tools: More than 120 filters ship with GIMP. Some filters apply a simple transformation to the current layer, while others do processor-intensive alterations to the entire image and sometimes even build a new image. Note that the word filter was used in a more specific way in Chapter 7. Some of the filters described in this chapter conform to that meaning; for example, Unsharp Mask and Convolution Matrix. Others are called filters simply because they are accessed from the Image: Filters menu.
In this chapter, we walk through almost all of the entries found in the Image: Filters menu. They have little in common besides being in the same menu. After trying in vain to find a logical way to organize this chapter, we decided to just follow the order of the menu. The GIMP developers devised this order using their own logic, and the order they came up with is as good as any we could think of. However, we will omit the following entries:
WEB is presented in Chapter 8.
ANIMATION is presented in Chapter 18, along with the other filters that are added by the GAP plug-in set.
PYTHON-FU and SCRIPT-FU deal with scripts and are presented in Chapter 21.
ALPHA TO LOGO contains a subset of the logo creation tools that appear in the Image: File > Create > Logos menu. They use the Alpha channel of the current image as the source of the logo, while the tools in the LOGOS sub-menu act on text. As explained in Chapter 4, we won’t cover them in this book since they’re self-explanatory.
We will also omit the following 10 filters, which we consider no longer useful to anybody: Erase Every Other Row, Video, Xach-Effect, Blinds, Predator, Slide, Filmstrip, Stencil Carve, Stencil Chrome, and Fog. In case you really need one of them, you’ll find its description on this book’s companion website.