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It is a way of encoding RGB information, and the actual color displayed depends on the actual RGB colorants used to display the signal. Therefore, a value expressed as Y′UV is only predictable if standard RGB colorants are used (i.e. a fixed set of primary chromaticities, or particular set of red, green, and blue).
For example, applying a histogram equalization directly to the channels in an RGB image would alter the color balance of the image. Instead, the histogram equalization is applied to the Y channel of the YIQ or YUV representation of the image, which only normalizes the brightness levels of the image.
Judd was the first to employ this type of transformation, and many others were to follow. Converting this RGB space to chromaticities one finds [4] [clarification needed The following formulae do not agree with u=R/(R+G+B) and v=G/(R+G+B)] Judd's UCS, with the Planckian locus and the isotherms from 1,000K to 10,000K, perpendicular to the locus.
YCbCr is sometimes abbreviated to YCC.Typically the terms Y′CbCr, YCbCr, YPbPr and YUV are used interchangeably, leading to some confusion. The main difference is that YPbPr is used with analog images and YCbCr with digital images, leading to different scaling values for U max and V max (in YCbCr both are ) when converting to/from YUV.
Here are grouped those full RGB hardware palettes that have the same number of binary levels (i.e., the same number of bits) for every red, green and blue components using the full RGB color model. Thus, the total number of colors are always the number of possible levels by component, n , raised to a power of 3: n × n × n = n 3 .
The three values of the YCoCg color model are calculated as follows from the three color values of the RGB color model: [2] [] = [] [] The values of Y are in the range from 0 to 1, while Co and Cg are in the range of −0.5 to 0.5, as is typical with "YCC" color models such as YCbCr.
A comparison between a typical normalized M cone's spectral sensitivity and the CIE 1931 luminosity function for a standard observer in photopic vision. In the CIE 1931 model, Y is the luminance, Z is quasi-equal to blue (of CIE RGB), and X is a mix of the three CIE RGB curves chosen to be nonnegative (see § Definition of the CIE XYZ color space).
RGB use in color space definitions employ primaries (and often a white point) based on the RGB color model, to map to real world color. Applying Grassmann's law of light additivity, the range of colors that can be produced are those enclosed within the triangle on the chromaticity diagram defined using the primaries as vertices .