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				Color Theory
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				.. For writing style guide, see: :doc:`/about/contribute/style_guides/writing_guide`
				If you add new entries, keep the alphabetical sorting!

				.. glossary::

				Alpha Channel
				Additional channel in an image for transparency.

				Straight Alpha
				Method where RGBA channels are stored as (R, G, B, A)
				channels, with the RGB channels unaffected by the alpha channel.
				This is the alpha type used by paint programs such as Photoshop or Gimp,
				and used in common file formats like PNG, BMP or Targa.
				So, image textures or output for the web are usually straight alpha.

				Premultiplied Alpha
				Method where RGBA channels are stored as (R × A, G × A, B × A, A),
				with the alpha multiplied into the RGB channel.

				This is the natural output of render engines,
				with the RGB channels representing the amount of light that comes toward the viewer,
				and alpha representing how much of the light from the background is blocked.
				The OpenEXR file format uses this alpha type.
				So, intermediate files for rendering and compositing are often stored as premultiplied alpha.

				Conversion (Straight/Premultiplied) Alpha
				Conversion between the two alpha types is not a simple operation and can involve data loss,
				as both alpha types can represent data that the other cannot though it is often subtle.

				Straight alpha can be considered to be an RGB color image with a separate alpha mask.
				In areas where this mask is fully transparent, there can still be colors in the RGB channels.
				On conversion to premultiplied alpha this mask is applied'
				and the colors in such areas become black and are lost.

				Premultiplied alpha, on the other hand, can represent renders
				that are both emitting light and letting through light from the background.
				For example, a transparent fire render might be emitting light,
				but also letting through all light from objects behind it.
				On converting to straight alpha, this effect is lost.

				Chroma
				Chrominance
				In general, a resulting image color decomposition, where its (L or Y) luminance channel is separated.
				There are two different contexts whereas this term is used:

				Video systems
				Refers to the general color decomposition resulting in Y (Luminance) and C (Chrominance) channels,
				whereas the chrominance is represented by: U = ( Blue minus Luminance ) and V = ( Red minus Luminance ).
				Matte compositing
				Refers to a point in the color gamut surrounded by a mixture
				of a determined spectrum of its RGB neighboring colors.
				This point is called Chroma key and this key
				(a chosen color) is used to create an Alpha Mask.
				The total amount of gamut space for this chrominance point
				is defined by users in a circular or square shaped format.

				Blend Modes
				Color Blend Modes
				Methods for blending two colors together.

				See also `Blend Modes <https://docs.gimp.org/en/gimp-concepts-layer-modes.html>`__ on GIMP docs.

				Color Space
				A coordinate system in which a vector represent a color value.

				RGB
				Red-Green-Blue traditional primary colors also broadcast directly to most computer monitors.
				HSV
				Three values, often considered as more intuitive (human perception) than the RGB system.

				Hue
				The Hue of the color.
				Saturation
				The quantity of hue in the color (from desaturated -- a shade of gray -- to saturated -- brighter colors).
				Value
				The brightness of the color (dark to light).
				HSL
				Hue, Saturation
				See HSV.
				Luminance
				TODO.
				YUV
				Luminance-Chrominance standard used in broadcasting analog PAL (European) video.
				YCbCr
				Luminance-ChannelBlue-ChannelRed Component video for digital broadcast use,
				whose standards have been updated for HDTV and commonly referred to as the HDMI format for component video.
				\+A
				The color space holds an additional :term:`Alpha Channel`.

				FSAA
				Full-Screen Anti-Aliasing
				A method of :term:`Anti-aliasing` on the graphics card, so the entire image is displayed smooth.
				Also known as Multi-Sampling.

				This can be enabled in the :ref:`User Preferences <prefs-system-multi-sampling>`.
				On many graphics cards, this can also be enabled in the driver options.

				Gamma
				An operation used to adjust the brightness of an image.

				See also `Gamma correction <https://en.wikipedia.org/wiki/Gamma_correction>`__ on Wikipedia.