Gerbil consists of an interactive visualization tool targeted at multispectral and hyperspectral image data, and a toolbox of common algorithms, e.g. for segmentation. Multispectral imaging has been gaining popularity and has been gradually applied to many fields besides remote sensing. However, due to the high dimensionality of the data, both human observers and computers have difficulty interpreting this wealth of information. Gerbil facilitates the visualization of the relationship between spectral and topological information in a novel fashion. It puts emphasis on the spectral gradient, which is shown to provide enhanced information for many reflectance analysis tasks. It also includes a rich toolbox for evaluation of image segmentation and other algorithms in the multispectral domain. The parallel coordinates visualization technique is combined with hashing for a highly interactive visual connection between spectral distribution, spectral gradient, and topology.