Colour theory and application
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Colour Theory and Application. B.Sc. (Hons) Multimedia Computing. Media Technologies. Agenda. Describing Colour Colour Models and Synthesis Colour Palettes Colours for the Web. B.Sc. (Hons) Multimedia Computing. Media Technologies. Describing Colour.

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Colour theory and application

Colour Theory and Application

B.Sc. (Hons) Multimedia Computing

Media Technologies


Agenda

Agenda

  • Describing Colour

  • Colour Models and Synthesis

  • Colour Palettes

  • Colours for the Web

B.Sc. (Hons) Multimedia Computing

Media Technologies


Describing colour

Describing Colour

  • Words we might use when naming and describing colours:

  • ‘shade, hue, warm, tone, bright, dim, pale, intense, vivid, rich, saturated, cold, strong, wishy-washy, glowing, colour, flat, weak, muddy, soft, vibrant, luminance, bold, tint’

  • Very subjective - influenced by perception and characteristics of illuminating light source.

B.Sc. (Hons) Multimedia Computing

Media Technologies


The visible spectrum

The Visible Spectrum


Colour temperature

Colour Temperature


The colour wheel

The Colour Wheel


Hue saturation value hsv

Hue, Saturation, Value (HSV)

The HSV model is based on the following concepts

  • Hue - this is what most people would refer to as the colour or shade. Red, yellow, green and blue are hues.

  • Saturation - this is a value that represents where the colour is on a scale from achromatic white to the pure hue.

  • Value - is the attribute, sometimes referred to as brightness, which determines how intense the colour is on a a scale from black to the pure hue.


Hsv 3d representation

HSV 3D Representation


Hsv 2d representation

HSV 2D Representation


The colour wheel maya

The Colour Wheel (Maya)

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour models

Colour Models

  • Additive Synthesis - Start with no light. Add red green and blue light to make white and complementary colours

  • Subtractive Synthesis start with white light. Subtract red green and blue light to achieve complementary colours and black

B.Sc. (Hons) Multimedia Computing

Media Technologies


Additive synthesis

Additive Synthesis

B.Sc. (Hons) Multimedia Computing

Media Technologies


Additive synthesis1

Additive Synthesis

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour models rgb

Colour Models:RGB

  • Display devices generally use a color model called RGB.

  • Stands for Red-Green-Blue

  • Based on the additive synthesis model

  • RBG colour value specified in three bytes

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour models rgb1

Colour Models: RGB

  • Each RGB value is given a number from

    0 – 255 starting from Black, R = 0 , B = 0, G = 0

    to White, R = 255 B = 255 B = 255

  • Thus 256 colours can be represented by one byte = 2 8

  • Total possible colours from RGB code is 255 x 255 x 255 = 16 581 375 colours = True colour, but will require 3 bytes per pixel ( 24 bit colour ).

B.Sc. (Hons) Multimedia Computing

Media Technologies


Subtractive synthesis

Subtractive Synthesis

B.Sc. (Hons) Multimedia Computing

Media Technologies


Subtractive synthesis1

Subtractive Synthesis

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour models cmyk

Colour Models:CMYK

  • Cyan-Magenta-Yellow-Black, and pronounced as separate letters. CMYK

  • Based on the subtractive synthesis model

  • CMYK is a colour model in which all colors are described as a mixture of these four process colours.

  • CMYK is the standard colour model used in offset printing for full-colour documents. Because such printing uses inks of these four basic colours, it is often called four-colour printing.

B.Sc. (Hons) Multimedia Computing

Media Technologies


Rgb additive

RGB Additive

  • Additive color: Combine light sources, starting with darkness (black).

  • The additive primary colors are red (R), green (G), and blue (B).

  • Adding R and G light makes yellow (Y). Similarly, G + B = cyan (C) and R + B = magenta (M).

  • Combining all three additive primaries makes white.

B.Sc. (Hons) Multimedia Computing

Media Technologies


Cmyk subtractive

CMYK Subtractive

  • Subtractive color: Illuminate objects that contain dyes or pigments that remove portions of the visible spectrum.

  • The objects may either transmit light (transparencies) or reflect light (paper, for example).

  • The subtractive primaries are C, M and Y.

  • Cyan absorbs red; hence C is sometimes called "minus red" (-R). Similarly, M is -G and Y is -B.

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour models rgb cmyk

Colour Models: RGB & CMYK

B.Sc. (Hons) Multimedia Computing

Media Technologies


Matching rbg to cmyk

Matching RBG to CMYK

  • One of the most difficult aspects of desktop publishing in colour is colour matching

  • Properly converting the RGB colours into CMYK colours so that what gets printed looks the same as what appears on the monitor.

  • RGB Most important for multimedia as it corresponds to the way colour is produced on a computer monitor


Rbg to cmyk photoshop

RBG to CMYK (Photoshop)


Palettes indexed colour

Palettes ( Indexed Colour )

  • Computer monitor may be able to display 24 bit colour but video driver hardware may be limited to less than 24 bit.

  • Thus use a subset of 24 bit in an 8 bit palette – a selection of colours appropriate to the image colours

  • Palettes provide a finite sub-set of colours required for a given image

  • If the colour requirements change then some colours in the palette will need to be substituted for others to enable the new colours to be represented

  • Approximation to original colour in scene

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour theory and application

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour palettes

Colour Palettes

  • Palettes provide a finite sub-set of colours required for a given image

  • If the colour requirements change then some colours in the palette will need to be substituted for others to enable the new colours to be represented

  • Approximation to original colour in scene

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour theory and application

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour theory and application

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour theory and application

B.Sc. (Hons) Multimedia Computing

Media Technologies


Web colours

Web Colours

  • Websafe colours were specified from the days when most of the web audience could only access 256 colours.

  • Most contemporary display hardware is now able to provide 24 bit colour

  • Still need to be aware of potential deployment issues for now.

B.Sc. (Hons) Multimedia Computing

Media Technologies


Colour theory and application

B.Sc. (Hons) Multimedia Computing

Media Technologies


Munsell system

Munsell System

  • Albert Henry Munsell

  • This system is based on the principle of "perceived equidistance”

  • Munsell attempts to account for each colour attribute in ordered visual steps. He introduced 100 steps for colour "hue", starting with five main colours and five additional colours, and adopts an ordering system with 10 units of colour "value" and an open scale called "chroma" (similar to saturation)

  • Used in paint industry and photographic applications


Munsell system1

Munsell System


References

References

The Colour Group ( founded in 1940 ) 19-11-04

http://www.city.ac.uk/colourgroup/

(City University)

Colour Wheel

http://www.ficml.org/jemimap/style/color/wheel.htm

Visbone Colour Resources 19-11-04

http://html-color-codes.com/l

Weinman L. Web Pallets 19-11-04

http://www.lynda.com/

Koren N. Light and Colour

http://www.normankoren.com/light_color.html 21-11-04

Roberts M HSV Colour Model. 21-1104

http://www.cs.bham.ac.uk/~mer/colour/hsv.html

Munsell System

http://www.colorsystem.com/projekte/engl/31mune.htm

B.Sc. (Hons) Multimedia Computing

Media Technologies


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