YUV
YUV is a color model typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, compared to a "direct" RGB-representation. Historically, the terms YUV and Y′UV were used for a specific analog encoding of color information in television systems. Today, the term YUV is commonly used in the computer industry to describe colorspaces that are encoded using YCbCr. The YUV model defines one luminance component (Y) meaning physical linear-space brightness, and two chrominance components, called U (blue projection) and V (red projection) respectively. It can be used to convert to and from the RGB model, and with different color spaces. The closely related Y′UV model uses the luma component (Y′) – nonlinear perceptual brightness, with the prime symbols (') denoting gamma correction. Y′UV is used in the PAL analogue color TV standard (excluding PAL-N). Previous black-and-white systems used only luma (Y′) information. Color information (U and V) was added separately via a subcarrier so that a black-and-white receiver would still be able to receive and display a color picture transmission in the receiver's native black-and-white format, with no need for extra transmission bandwidth. As for etymology, Y, Y′, U, and V are not abbreviations. The use of the letter Y for luminance can be traced back to the choice of XYZ primaries. This lends itself naturally to the usage of the same letter in luma (Y′), which approximates a perceptually uniform correlate of luminance. Likewise, U and V were chosen to differentiate the U and V axes from those in other spaces, such as the x and y chromaticity space. See the equations below or compare the historical development of the math. (Wikipedia).
