Colour

1. Percieving Colour

A pure color is a wave with wavelength and intensity . In practice light has a mixture of wavelengths with an energy distribution. Most colours we can perceive can be represented as a linear combination of basis functions , and . A CIE diagram is a 2D representation of the color space, where each point corresponds to a color. The x and y coordinates represent the chromaticity, while the z coordinate represents the luminance.

The edges of the horseshoe are coherent , and the colours inside can only be represented as a mixture of the pure colours on the edge. The white point is the point where all three basis functions are equal, and represents the color white. It is located when at .

A diametrically opposite colour (through the white point) is called a complementary colour.

Displays produce a triangular subset of the colors in the CIE diagram, and the vertices of the triangle correspond to the primary colors used by the display.

1.1 Subtractive Primaries

Used when printing, where inks absorb wavelengths from the incident light. We use Magenta, Cyan and Yellow as the primary colours.

2. HSV

Digital artists may use Hue, Saturation & Value color space. To convert from RGB to HSV:

• is an angle between and is computed procedurally.

3. Alpha Channel

The alpha component of colour is an attenuation of the intensity (typically transparency).