RGB coding

The RGB coding (Red, Geen, Blue), developed in 1931 by the International Lighting Commission (Commission Internationale de l'Eclairage, CIE) consists in representing the colour space with three monochromatic rays, with the following colours:

• Red (with a wavelength of 700.0 nm),
• Green (with a wavelength of 546.1 nm),
• Blue (with a wavelength of 435.8 nm).

This colour space corresponds to the way in which the colours are usually coded on a computer, or more precisely to the way in which the computer screen cathode tubes represent the colours.

Thus, the RGB model proposes each colour component to be coded on one byte, which corresponds to 256 intensities of red (2⁸), 256 intensities of green and 256 intensities of blue, thus, there are 16777216 theoretical possibilities of different colours, that is, many more than the human eye can distinguish (approximately 2 million). However, this value is only theoretical because it strongly depends on the display device being used.

Since RGB coding is based on three components with the same proposed value range, it is usually graphically represented by a cube of which each axis corresponds to a primary colour:

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