Graphics

• Video processing relies on image processing underneath.
• The human retina is composed of  three kinds cells called cones:
• Long wavelength, approximately red.
• medium wavelength, approximately green
• Short wavelength, approximately blue
• Three quantities, therefore,  are enough to uniquely identify a color humans can see.

 Color models 

A color model is a mathematical way of describing colors. It is independent from physical devices. 

• Linear models: (x, y, z ..) ==> discrete value
• The red-green-blue (RGB) model
• RGBA model: an extension of RGB with an alpha parameter, which specifies the opacity for a color. The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).
• CMYK model (Cyan, Magenta, Yellow and Black)
• Spectral models 

 

 Color spaces

A color space is the method of mapping real colors to the color model's discrete value.
In a color model, the same discrete value, (x, y, z ..), identify a different-appearing (real) color in different color spaces.