From GIMP Developer Wiki
Revision as of 13:18, 5 January 2014 by Scl
This glossary holds definitions important for the GIMP development. These include functional definitions i.e. from computer graphics and color theory, photography, terms from BABL and GEGL etc.
Table of Contents
- 'A (uppercase)' -
- The alpha channel in a color model, for instance in RGBA.
- In babl the alpha value in a color model. If combined with alpha-premultiplied color channels: the alpha value each color channel R, G, B was multiplied with to achieve Ra, Ga, Ba. Needed to get from RaGaBa back to RGB. The same applies to R'aG'aB'aA, YaA, Y'aA.
- 'a (lowercase)' -
- 'Alpha' - opacity. An alpha value of 0 means 'transparent', an alpha value of 100 means 'fully opaque', values in between mean 'partly opaque'.
- 'B (uppercase)' -
- Blue color channel in the XYZ and RGB color models.
- brightness component of the HSB color model.
- In photography: symbol for brightness: obsolete, but may be found on older light meters. 
- Bulb (in photography): Used for long exposures timed by the photographer. Setting for shutter at which shutter opens when shutter button is pressed and stays open as long as shutter button is kept down. 
- 'b (lowercase)' - the axis in the CIELAB color space which denotes the blue-yellow component of the image. One end of the axis is blue and the other end yellow. 
- 'babl' - a dynamic, any to any, pixel format translation library.
See also: babl website
- 'brightness' - attribute of a visual perception according to which an area or color appears to emit, or reflect, more or less light. This correlates directly with the amplitude of the lightwave.   Translation glossary
- 'C (uppercase)' -
- 'CIE' - Commission Internationale de l´Eclairage (International Commission on Illumination). Independent, non-profit organization for recommendations on photometry and colorimetry. Its aim is to exchange information on all matters relating to the science and art of light and lighting, colour and vision, photobiology and image technology worldwide. It is recognized by ISO as an international standardization body. The CIE has defined several "color spaces" that describe the range of visible colors in unambiguous numerical terms.  
- 'CMY' - Cyan, Magenta, Yellow. The three "subtractive" primary colors used as the basis of all dye or pigment-based printing systems and color photography. A full range of colors including neutral grays and blacks can be produced with good cyan, yellow and magenta colorants (e.g. color film dyes) but typical printing inks are less than perfect. 
- 'CMYK' - Cyan, Magenta, Yellow, Key color (usually Black). The four colors commonly used in process color printing. Black is added to CMY to enhance the density of dark areas and solve gray balance problems encountered when trying to make neutral grays with CMY alone. 
- 'color temperature' - temperature of an ideal black body radiator whose radiation has the same chromaticity as that of a given stimulus. Unit: K (Kelvin). 
- 'chroma' - colorfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting. The higher the chroma, the more saturated this area appears.  
- 'chromaticity' - The color properties of a sample judged independently of luminance, i.e. in terms of hue and saturation only. 
- 'GEGL' - Generic Graphics Library, a graph based image processing framework. It is GIMP's foundation for nondestructive image editing in high bit depths. GEGL provides the infrastructure to do demand based, cached, nondestructive image editing on larger than RAM buffers. Through babl it provides support for a wide range of color models and pixel storage formats for input and output. GEGL support in current GIMP versions is experimental and will be official part of GIMP in version 2.10.
See also: GEGL website, GEGL porting matrix
- 'GSoC' - Google Summer of Code. Annual mentoring program hosted by Google Inc. to offer and award students to work on open source projects during summer. GIMP has been participating for many years.
See also: GSoC website, GIMP's GSoC participation
- 'K (uppercase)' -
- 'LGM' - Libre Graphics Meeting. Annual conference of developers and users of graphics open source software. GIMP has been participating for many years. Website
- 'light, linear' - light as it is in nature and captured by camera sensors (and thus is encoded in RAW images).
- 'light, percepted' - light as it is processed by eye and brain. The difference between linear and percepted light is that human eyes react to the same change of (linear) light with different sensitivity in dark or light environments. Percepted light is the basis of color (e.g. color is the result of light, processed by eyes and brain).
- 'Mired' - former, obsolete unit of reciprocal color temperature .
- 'Y (uppercase)' -