Prof. Muhammad Saeed. FUUASTDept. Comp. Sc. & IT2 Wavelength Note that the rainbow does not contain any magenta. It is nonspectral. Color Models:

Prof. Muhammad Saeed

FUUAST Dept. Comp. Sc. & IT 2

Wavelength

Note that the rainbow does not contain any magenta. It is nonspectral.

Color Models:


Newton’s Color Wheel Newton’s Color Wheel Replaced Aristotle’s color model based on light and darkness.

Color Models:


Color Models:

Spectrumultraviolet light

Wavelength (nm)700 600 500 400

• Seen in physics, physical phenomena (rainbows, prisms, etc)

• 1 Dimensional color space

Infrared light

http://elchem.kaist.ac.kr/vt/chem-ed/light/graphics/em-visib.jpg


Sensitivity and Models


Tristimulus Color TheoryTristimulus

Color Theory

• Any color can be matched by a mixture of three fixed base colors (primaries)

• Eye has three kinds of color receptors called cones

• Eye also has rods (low light receptors)

Color Receptors in EyeColor Receptors in Eye

0.20

0 .18

0 .16

0 .14

0 .12

0 .10

0 .08

0 .06

0 .04

0 .02

0 .00600560440 520 640400 680480

Wavelength λ (nm)

Fra

ctio

n o

f lig

ht

abso

rbed

by

each

ty

pe

of

con

e

Color Models:


Wavelength is in nanometers

Color Models:


Traditional, Artistic:• RGB

• CMY

• CMYK

• HSV

• HSL

Perceptually Based:• XYZ (Tristimulus)• Xyz• Hunter-Lab• CIE-L*ab• CIE-L*CH° • CIE-L*CH°• CIE-L*ab• CIE-L*uv

Color Models:


Color Models:

Tints, Tones and Shades:

White Pure Color

Black

Shades

Tones

Grays

Tints


Additive Primaries: (r,g,b)Additive Primaries: (r,g,b)

(1,0,1)(1,0,1)

(0,0,1 )(0,0,1 )

magentamagentamagentamagenta

whitewhitewhitewhite(1,1,1)(1,1,1)

(0,1,0)(0,1,0)greengreengreengreen

(1,1,0)(1,1,0)yellowyellowyellowyellow

(0,1,1)(0,1,1)cyancyancyancyan

blueblueblueblue

(1,0,0)(1,0,0)redredredred

Color Models:


Color Models:

(0,0,1 )(0,0,1 )blueblueblueblue

(1,0,1)(1,0,1)magentamagentamagentamagenta


(0,1,0)(0,1,0)



whitewhitewhitewhite(1,1,1)(1,1,1)

(0,0,0)(0,0,0)blackblackblackblack

graygraygraygray

RGB Model:

greengreengreengreen


(0,0,1 )(0,0,1 )blueblueblueblue




(1,1,0)(1,1,0)yellowyellowyellowyellow(1,0,0)(1,0,0)

redredredred

(1,1,1)(1,1,1)whitewhitewhitewhite

Color Models:


Looking at color cube along major diagonal

Color Models:


(0,0,1)(0,0,1)

Color Models:




blueblueblueblue



blackblackblackblack(0,0,0)(0,0,0)

Subtractive Primaries: (r,g,b)Subtractive Primaries: (r,g,b)


120˚

0˚

V

SH

1.0

0.0

240˚

yellowyellowyellowyellowgreengreengreengreen

cyancyancyancyanredredredred

magentamagentamagentamagentablueblueblueblue

• Introduced by Albet Munsell, late 1800s.

• He was an artist and scientist

• Hue: Color

• Saturation/Chroma: Strength of a color

– Neutral gray has 0 saturation

• Brightness/Value:

• Intensity of light emanating from image

Color Models:

H S V MODELH S V MODEL


SaturationColor Models:


James C. Maxwell’s Color ModelJames C. Maxwell’s Color Model

magentamagentamagentamagentablueblueblueblue

cyancyancyancyan

greengreengreengreen

redredredred

yellowyellowyellowyellow

unsaturated cyan unsaturated cyan unsaturated cyan unsaturated cyan

whitewhitewhitewhite

Color Models:


1.0

S

L

0˚

0.0

H


blackblackblackblack

redredredred

Color Models:

HLS Model (Hue, Lightness, Saturation)


Color Models:

HSV to RGB


Color Models:

RGB to HSV


Color Models:

CIE* Color SpaceCIE* Color Space

( X, Y, Z ) represents an imaginary basis that does not correspond to what we see

Define the normalized coordinates:x = X / ( X + Y + Z )

y = Y / ( X + Y + Z )

z = Z / ( X + Y + Z )

* Commission Internationale de l'Êclairage


x + y + z = 1

x = X / ( X + Y + Z )

y = Y / ( X + Y + Z )

z = Z / ( X + Y + Z )

z

y

x

The projection of the plane of the triangle onto the (X,Y) plane forms the chromaticity diagram that follows.

Color Models:

CIE Color Space of Visible ColorsColorsCIE Color Space of Visible ColorsColors


Color Gamuts: CIE Color ChartColor Gamuts: CIE Color Charty

x

1.0

0 .9

0 .8

0 .7

0 .6

0 .5

0 .4

0 .3

0 .2

0 .1

1.0 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1.0

cyancyan

magentamagentaredredblueblue

green green

yellowyellow

400

490

500

510

520

600

700

580

560

540


Color Models:


ideal redideal redideal redideal redideal blueideal blueideal blueideal blue

ideal greenideal green ideal greenideal green

redredredredblueblueblueblue

green green green green

cyancyanyellowyellow


400 nm

490 nm

500 nm

510 nm540 nm

560 nm

580 nm

700 nm

600 nm

520 nm

Color Gamuts: CIE Color ChartColor Gamuts: CIE Color Chart

Color Models:


400

490

500

510

520

600

700

580

560

540

Color Gamuts: CIE Color ChartColor Gamuts: CIE Color ChartColor Models:


400

490

500

510

520

600

700

580

560

540

R

B

G

The Color Gamuts of different displays and printers are not likely to match. Printers usually have smaller gamuts.



Color Models:

CIE Chromaticity Diagram:

ZYX

Xx

ZYX

Yy


400

490

500

510

520

600

700

580

560

540

C2

C3

C1

The additive colors C1and

C2 combine to

form C3 on the

line connecting C1 and C2.



Color monitors are based on adding three the outputof three different light emitting phosphors.

The nominal position of these on the CIE diagram isgiven by: x y zRed 0.628 0.346 0.026Green 0.268 0.588 0.144Blue 0.150 0.07 0.780

Color Models:

Reproducible colors:


Color Models:

The monitor RG B representation is related to the CIE colors by the equation:

RGB to CIE:

B

G

R

zyx

78.0144.0026.0

07.0588.0346.0

15.0268.0628.0

Color (RGB) to Gray Transformation:Red *= 0.33,Green *= 0.56,Blue *= 0.11


CIE Chromaticity Diagram

Color Models:

CIE Model (Commission Internationale de I’ Eclairage):


Color Models:

Gamma Correction:

1'

'

)(

)(

ii

im

RkR

RKR


Prof. Muhammad Saeed. FUUASTDept. Comp. Sc. & IT2 Wavelength Note that the rainbow does not contain any magenta. It is nonspectral. Color Models:

Documents

cie color chart color

color rgb

image color models

nanometers color models

uv color models

it4 color models

it27 color models

it32 color models