Computer Graphics

Tomas Vanicek

College of Civil Engeneering, B407

vanicek@fsv.cvut.cz

http://kix.fsv.cvut.cz/vanicek

Methods of graphical information saving

• Grid

• Vector

Grid formats

Colours in Computer Graphic

Electromagnetic Waves

Visible light

• Frequency 3.8×1014 Hz až 7.5×1014 Hz

• Wavelength 800nm – 400nm = 8-4×10-7m

Colour perception – Spectral function

Colour Models

• The spectral functions forms vector space of infinity dimension

• Human eye can recognize only 10.000 – 50.000 colour hues

• In fact only 3 dimensional vector space is usually sufficient

• We must chose 3 vector of base, 3 basic colour, for example Red (R), Green (G) and Blue (B)

RGB model

Aditive composition of colours

RGB – 8 basic colours

RGB – 256 colours

• 8 x 8 x 4 partion

RGB True Color

• 256 x 256 x 256 = 16.777.216 colours

CMY model

• Subtractive composition of colours

CMYK model

• Colour K made from CMY is not precise

• It is cheaper

Model HLS (Hue, Light, Saturation)

Light

S

Model HLS