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. - PowerPoint PPT PresentationTRANSCRIPT
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
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
Colour Temperature
The Colour Wheel
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 2D Representation
The Colour Wheel (Maya)
B.Sc. (Hons) Multimedia Computing
Media Technologies
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
B.Sc. (Hons) Multimedia Computing
Media Technologies
B.Sc. (Hons) Multimedia Computing
Media Technologies
Additive Synthesis
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: RGB
Each RGB value is given a number from0 – 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
B.Sc. (Hons) Multimedia Computing
Media Technologies
B.Sc. (Hons) Multimedia Computing
Media Technologies
Subtractive Synthesis
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
B.Sc. (Hons) Multimedia Computing
Media Technologies
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.
CMYK Subtractive
B.Sc. (Hons) Multimedia Computing
Media Technologies
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.
Colour Models: RGB & CMYK
B.Sc. (Hons) Multimedia Computing
Media Technologies
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)
Palettes ( Indexed Colour )
B.Sc. (Hons) Multimedia Computing
Media Technologies
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 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
B.Sc. (Hons) Multimedia Computing
Media Technologies
B.Sc. (Hons) Multimedia Computing
Media Technologies
B.Sc. (Hons) Multimedia Computing
Media Technologies
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
B.Sc. (Hons) Multimedia Computing
Media Technologies
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 System
References
B.Sc. (Hons) Multimedia Computing
Media Technologies
The Colour Group ( founded in 1940 ) 19-11-04http://www.city.ac.uk/colourgroup/(City University)
Colour Wheelhttp://www.ficml.org/jemimap/style/color/wheel.htm
Visbone Colour Resources 19-11-04http://html-color-codes.com/l
Weinman L. Web Pallets 19-11-04http://www.lynda.com/
Koren N. Light and Colourhttp://www.normankoren.com/light_color.html 21-11-04
Roberts M HSV Colour Model. 21-1104http://www.cs.bham.ac.uk/~mer/colour/hsv.html
Munsell Systemhttp://www.colorsystem.com/projekte/engl/31mune.htm