Contemporary Economic Issues Facing the Filipino Entrepreneur (1).pptx
Colours
1. Colour Theory and Application
B.Sc. (Hons) Multimedia Computing Media Technologies
2. Agenda
Describing Colour
Colour Models and Synthesis
Colour Palettes
Colours for the Web
B.Sc. (Hons) Multimedia Computing Media Technologies
3. 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
9. Using the Colour Wheel
Colour Wheel video
http://www.youtube.com/watch?v=59QGexKdFUI
10. What about text?
A useful interactive tool:
http://www.hgrebdes.com/colour/spectrum
So, text is different!
You need contrast – but not too much.
11. Colour Models:RGB
Display devices generally use a color model
called RGB.
It stands for Red-Green-Blue
Based on the additive synthesis model
RGB colour value specified in three bytes
B.Sc. (Hons) Multimedia Computing Media Technologies
12. 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
13. How’s your Hexadecimal?
Base 10 digits= 0 -> 9
Base 2 digits = 0 -> 1
Base 16 digits = 0 -> F
Why?
So each byte goes from 00 -> FF
So FF FF FF (R,G,B) = ?
And 00 00 00 =?
80 80 80 = ?
FF 80 80 = ?
14. Colour Models: 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.
17. The Colour Picker (Maya)
B.Sc. (Hons) Multimedia Computing Media Technologies
18. Colour Models: Synthesis
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
20. 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
23. 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
26. Colour Models:CMYK
Cyan-Magenta-Yellow-Key, and pronounced as
separate letters. CMYK
Based on the subtractive synthesis model
CMYK is a colour model in which all colours 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.
Key is (usually) black – although, in theory, black can be
produced with C+M+Y, it looks muddy and most colour
printers have a separate black ink cartridge.
B.Sc. (Hons) Multimedia Computing Media Technologies
28. 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
30. Palettes (Indexed Colour)
Computer monitors may be able to display 24 bit colour but
video driver hardware may be limited to less than 24 bit.
Thus we 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
38. Web Colours
Websafe colours were specified from the days
when most of the web audience could only
access 256 colours.
To display intermediate shades, ‘dithering’ was
necessary.
Most contemporary display hardware is now
able to provide 24 bit colour
Still need to be aware of potential deployment
issues for now (e.g. mobile phones)
B.Sc. (Hons) Multimedia Computing Media Technologies
40. 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
43. 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