Color gradient
In computer graphics, a color gradient specifies a range of position-dependent colors, usually used to fill a region. For example, 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. A color gradient is also known as a color ramp or a color progression. In assigning colors to a set of values, a gradient is a continuous colormap, a type of color scheme. Definitions. Strict definition. A colormap is a function which associate a real value r with point c  in color space formula_1 which is defined by: where: Types. Criteria for classification: Shapes. Axial gradients. An axial color gradient (sometimes also called a linear color gradient) is specified by two points, and a color at each point. The colors along the line through those points are calculated using linear interpolation, then extended perpendicular to that line. In digital imaging systems, colors are typically interpolated in an RGB color space, often using gamma compressed RGB color values, as opposed to linear. CSS and SVG both support linear gradients. Radial gradients. A radial gradient is specified as a circle that has  one color at the edge and another at the center. Colors are calculated by linear interpolation based on distance from the center. This can be used to approximate the diffuse reflection of light from a point source by a sphere. Both CSS and SVG support radial gradients. Conic gradients. Conic or conical gradients are gradients with color transitions rotated around a center point (rather than radiating from the center). Example conic gradients include pie charts and color wheels. Other shapes. In vector graphics polygon meshes can be used, e.g., Adobe Illustrator supported "gradient meshes". Effect of color space. The 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: 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.