The GIMP uses three formats for displaying and working with images. These are the RGB, Grayscale, and Indexed formats. Although Grayscale is discussed briefly in Chapter 5 and Indexed format in Chapter 9, the primary format used in this book is RGB.
Because most GIMP plug-ins do not work on Indexed image formats, it makes sense to immediately convert an indexed format image to RGB when it is first loaded into the GIMP. Conversion to RGB is performed with the RGB function found in the Image:Image/Mode menu.