HSI、HSL and YCrCb

HSI

Tone and saturation are often referred to as chromaticity to indicate the type and depth of a color.

Since human vision is much more sensitive to Brightness than to color intensity, in order to facilitate color processing and recognition, human visual system often USES HSI color space, which is more in line with human visual characteristics than RGB color space.

Hue: The wavelength of conduction or reflection from an object. More commonly, colors such as red, orange, or green are identified on a scale of 0 to 360 degrees.

Saturation (Saturation) : Also known as chroma, refers to the strength or purity of colors. Saturation represents the ratio of grey to hue and is measured in terms of 0% (grey) to 100% (full saturation).

Intensity: the relative Intensity of the color, usually measured in percentages from 0% (black) to 100% (white).

HSL

HSL stands for hue, saturation, and lightness

HSL conceptually represents a double cone and sphere (white at the top, black at the bottom, and the center of the maximum cross section is half-grey)

Hue determines the nature of color, and when we say red, orange, and yellow, we mean a hue.

Saturation refers to the proportion of the color. The deeper the color, the higher the degree of saturation; the higher the proportion of white, the lower the degree of saturation.

Brightness indicates the lightness of a color, with the larger the value, the brighter it is.

YCrCb

Y is Luminance, Cb and Cr are chrominance, Cb and Cr are blue and Cr are red. Although RGB and YCbCr cannot save storage space for the three channels, they can actually reduce the memory by using the feature that human vision is more sensitive to brightness but less sensitive to chrominance, that is to say, the number of samples Cb and Cr can be reduced.