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Unformatted text preview: o 500 nm
cannot be generated
cannot CIE Color Space
No standard set of three wavelengths can be
No
combined to generate all other wavelengths.
combined
The CIE (Commission Internationale d’Eclairage)
The CIE
defined three hypothetical lights X, Y, and Z with
these spectra:
these
Idea: any wavelength λ can
Idea:
be matched perceptually
by positive combinations
positive
of X, Y, and Z
of x~R
y~G
z~B CIE Color Space
The gamut of all colors perceivable is thus a threeThe gamut
dimensional shape in X, Y, Z
Color = xX + yY + zZ CIE Chromaticity Diagram (1931)
For simplicity, we often
project to the 2D plane
x+y+z=1
x = x / (x+y+z)
y = y / (x+y+z)
z=1–xy Device Color Gamuts
Since X, Y, and Z are hypothetical light sources,
Since
no real device can produce the entire gamut of
perceivable color
perceivable
Example: CRT monitor Device Color Gamuts
We can use the CIE chromaticity diagram to
We
compare the gamuts of various devices:
compare
Note, for example,
Note,
that a color printer
that
cannot reproduce
all shades available
on a color monitor A Problem With XYZ Colors
If we have two colors C1 and C2, and we add ∆ C
If
to both of them, the differences between the
original and new colors will not be perceived to
not
be equal
be
This is due to the variation of the just noticeable
This
differences in saturated hues
differences
XYZ space is not perceptually uniform
XYZ
perceptually
LUV space was created to address this problem RGB Color Space (Color Cube)
Define colors with (r, g, b) amounts of red, green,
Define
and blue
and RGB Color Gamuts
The RGB color cube sits within CIE color space
The
something like this:
something Converting Color Spaces
Simple matrix operation: R ' XR
G ' = YR B ' ZR XG
YG
ZG XB R YB G ZB B The transformation C2 = M12 M1 C1 yields RGB on
The
monitor 2 t...
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This note was uploaded on 01/23/2012 for the course CS 445 taught by Professor Bloomfield,a during the Spring '08 term at UVA.
 Spring '08
 BLOOMFIELD,A
 Computer Graphics

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