appearance of a gradient not only varies by the color themselves, but also by the color space the calculation is performed in. The problem usually becomes important for two reasons: Gamma correction to a color space. With a typical γ of around 2, it is easy to see that a gamma-enabled color space will blend darker than a linear-intensity color space, since the sum of squares of two numbers is never more than the square of their sum. The effect is most apparent in blending complementary colors like red and green, with the middle color being a dark color instead of the expected yellow. The radial and conic examples on this page clearly exhibit this error. Handling of other perceptual properties. In information visualization, it is undesirable to have a supposedly "flat" gradient show non-monotonic variations in lightness and saturation along the way. This is because human vision emphasizes these qualities, causing bias or confusion in interpretation. A "linear" blend would match physical light blending and has been the standard in game engines for a long time. On the web, however, it has long been neglected for both color gradients and image scaling. Such a blend still has a subtle difference from one done in a perceptually-uniform color space. Examples HSV rainbow File formats Extensions: GIMP .gpl Adobe .aco, .acb, .act, .ase, .acf, .bcf, .clr AutoCAD .acb ColorSchemer .cs Corel .cpl, .xml (X5) ICC named color .icc OO.o .soc QuarkXPress qcl (+cui) RAL .bcs RIFF .pal Scribus .xml VivaDesigner .xml Applications represent quantitative or ordinal values, like in heat maps. More precise description is in color box. fill a region: many window managers allow the screen background to be specified as a gradient. The colors produced by a gradient vary continuously with position, producing smooth color transitions. visualize the progression of an extended computer operation, such as a download, file transfer, or installation. See progress bar Weblinks See also Bokashi (printing) Color banding Color difference Color mapping; a function that maps (transforms) the colors of one image to the colors of another image Diffusion curve dithering Image gradient Mach banding Ombré Palette; a finite set of colors in no particular order Perceptually uniform color spaces Posterization Color chart swatch books ( like in Paper color swatch book or RAL CLASSIC K5 colour fan or Pantone color guides) References Computer graphics