What is HSV? Where is it used? How does it differ from HSL?

HSV (Hue, Saturation, Value) is a color representation system that uses three parameters to define color. It is similar to HSL (Hue, Saturation, Lightness), but uses "Value" instead of "Lightness". 

Hue: Defines the type of color and its position on the color wheel. Hue is measured in degrees and can take values from 0 to 360.

Saturation: Defines the saturation of the color. Saturation values range from 0 to 100%, where 0% means no color (hue in grayscale), and 100% means maximum saturation.

Value: Defines the brightness or intensity of the color. Values are measured from 0 to 100%, where 0% is black, and 100% is maximum brightness.

HSV is often used in graphics, graphic design, and image processing, as it allows for convenient manipulation of color aspects such as hue, saturation, and brightness. The alpha channel is absent in the original HSV model. However, just like in HSL, there are extended versions of HSV, such as HSVAA, where an alpha channel is added to define color transparency. The HSVA format allows using HSV to define color and add an alpha channel to control transparency. 

Just like with HSL - the total number of possible colors is: 360×101×101=3,656,400.

Hue, saturation, and value (Hue, Saturation, Value or HSV) and hue, saturation, and lightness (Hue, Saturation, Lightness or HSL) represent two different color representation models, although they have a similar format. The main differences between them manifest in the ways brightness is defined and the interrelationship of parameters.

In the HSV (Value) model, the "Value" parameter is used, which defines the brightness or intensity of the color, with possible values from 0 to 100%, where 0% represents black, and 100% represents maximum brightness. In the HSL (Lightness) model, the "Lightness" parameter is used, which also defines the brightness of the color, and the lightness value can also vary from 0 to 100%, but hue and saturation remain unchanged when lightness changes.

The HSV model describes colors as perceived by the human eye. The "Value" parameter defines brightness regardless of lighting conditions, serving as an indicator of color intensity. The HSL model describes colors in the context of interaction with lighting. The "Lightness" parameter reflects how light or dark a color appears under specific lighting conditions.

In the HSV model, changing brightness does not affect hue or saturation, making this model convenient for reproducing hues at different brightness levels. On the other hand, in the HSL model, changing lightness can affect hue and saturation, allowing for consideration of lighting when defining color.

The HSV model is often used in computer graphics and design for working with colors, as it allows for effective control over brightness. The HSL model is also applied in graphics and design, sometimes considered more convenient for defining the appearance of colors in the context of lighting.