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Oolour
(0۵0990
۱
Rod OoParkrnd
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Oue, Chupter
svieue oP colour visioa الك
weusurewed systews owed stoadacds ماو
Oppowed provess thepry
Opphcaticces
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لجد دمجاو ررد ودوجلل دوس Colouw
stoadards
* ap colo coo be wotcked امیس و نی oF
three “privvaries”.
C=rR+ gG+ bB
٠ Phe priwores oe wit vevessurilpy red, yoru, und
blue. (Bap three diPPeredt colours coo be used. Mae
reage oP colours thot coo be produced Pros o qived set
DP priwunes is the youu.
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ty colours. موه رل
7 بلا ای "لسن ما
اما لصا بت را لو
ال
“7 tp the socve مسا وه
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018 —- Chrowntivity
۳ رت ۰9
Brow trisioutis volues! ام كك
٠ Giwe xtytz=d, just we
x, بز vdtues ood میا
0 |( ۳(
سس ‘ey SS بل م0 ۰
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Ovlouw Gpave - C1Chw ماه(
= Gpepficaicd of colour tolercac
= Oo vine (cantar deer)
- Peeudoorour sequences و
represed مد اس
ا جا spar *
وكاس
ته كه كه 04 03 a2 له oo بموحن و ليو 201 2
chrowaticty dragron
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۰ حول بیان owt solve dl problews:
=) nN
— Goll colour patches: dPPicdt to disttrguish oolours it
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Oppovett provess thepry
© Ohoch-white (huwicrare), red-
reed, ood bhue-pelow vppoorcts
٠ Wes basis ia biology cod mule
© Ghoud use oppooedt colours Por
vodicg data
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(Properties اون ام Chaccels
5 sckrvicca / Pqubuertavus poteras! 3 oolvur
potters whose cowpourcs do ot dP er it
foci
اه موی جاأوجججات صن أجاء يصاصر لحجه موصصي- لج © 5
about W/9 oP the deta canied by black-white.
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ort en Or) NM oe Ne aU) ل
nia Pala VA PA a at hs eto ped een Baca ASIN يا
OS Shs cca nea 0 ane ANAS
eel Cleaner epee ae Ne i pried ل PRUE
a SN Da IND Exch erg ل Peed Pd
اوداك 9
mee ira eee ۱
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وه ماو مان
۰ Gterevsvvpic depth is unt detectable wits
isvhucviecnt colours
۱ it uppeur to be
slower theo the soe coisvaticg to سوواط
white
۰ Skope ued Por we best show حاكن
“ee
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* منم ماو
— Osturd Ovtour Gystew (DOG) ey. 090-0700
* Okockeess OO, ntevsiy OO, yer OO, pelo CO
— Posivar, Ouasell: stradad colvur chips
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5 Colour Por ماه اممنمیم) باه
Purvis)
— Osiuctcess
* @ rapidly distrquished colour lies وه عاا عون
poled dePiced by the other colours ic O18 space
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5 Colour Por tabetticy (C)
— Ovique hues! “usiversuly revoysized” hues (red,
reed, blue, yellow, black, white) should be used
— Contrast with backyvudd: border anu obievts
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5 0 باه ۲ عروام )9(
- سای وه وروی :دوعصلصناط عسموان() people
pont distiocuish ned-qreru, but wost people vod
EE 111111
= Durcber! ody GID codes raniy dotecnished
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© Colour Por labeticg (P)
— Gre
۰ لاله واه لجوج سواو0) wt be very sual (about 2
deqrer wicivun size).
* Goooler objevis should be wore high) scturcied, barge
volou-voded reqivas should have bow soturaica. Text
لته رن be .وصاسف رها روم
عمطاهورمول) -
رمک و و2 باه ۲و وم Cowon *
.. .لامصمخصاط
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5 Colour Por بجناعماما )©(
خاج له )ماه لول مومس ©) دده () -
prePerewer):
0 9 000 6
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۱
— Pseudocolouriey is the procice oP ussiqnicgy colour to
wup udues thot do ot represeut colour
٠ Dediodt imagery
° Ostrowwird mayer
* Quppicg سوت موه ارو to the visible
spevinny (usirvorwy, Prored inaes)
— Gray soe best Por skhowiey surPuce shupe
— Colour best Por chissPication
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(9) موه ۲ ون ٠
- )۳ ۳ هوجو طط black-white, red-grerd, bhue-
(لششانل) مه اه نامر sequeure cod be used.
— or detailed dota, the sequeue should be bused woidy oo
hospice. (Por tow tetal, cholic or soturcive se queWwEs
vad be used.
— OvPors colour spuwes coo be used to oredte color
sequewes where equ percept steps correspoud to equal
— Okere itis ispportodt to be oble to read oPP dues Prow a
volour wup, 0 sequedce thot cycles through wos colours is
prePercble.
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سره
۰ Colour Por wappicry (O)
— 8 “opr! thr cob spare (evoke اجه
Ane 0, 90,... C30, #9, 99.
lawn 0, 29, 90... 889
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5 موه ۲ اون )4(
— Pervepiod مره P the sequeue is swootk, people
tecd to see سول colours, potest سای
dota.
* Op persond diisivg ito blue, yreru, yellow, crane, red,
اه رو سم
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* Colour ۳ رومض (S)
— Osiag colour Por O-O و موه
* OR Rica to reed accurately
* Oa be wed to death مزر
° Gotelite موز موم oP fovisible spectre wupped to
red, grees, blue choooels
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* Colour Por wutidioecsiccd discrete data
—S-O plot sien (x, v) روصم red, yreru, blue
— Possible to identiPy clusters
— @oobiquous: is 3 potet لها or #موص ره
— Other wethods ceeded to codlae chisters وحمت
سل
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oxyowitz ef of.
Wow Oot to Lie wit Oisuctzaicd
* Oise represeotaivd of dota oPPevts the perceived
feds: اد
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Colour
erveptud ismpact oP oo oolour is unt predictable Prow the
red/qrecd/blue vowpocrcts oP the olor
لاد مرو( uspevis oP colour to diPPereut data is
OePout colour waps! robow
— Percept avotaeaniy
— Case coviours
— Yellow otras ماه
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whe وموم ای ۲و اوه ها تون
user based put
— Ota type
— Onte spotid Prequeccy
= Ovolzaica task
= Other desiqa choices wade by ser
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Represeuticcy ©
data اومی()
— Objert should be distiocpuishably dPRerecot but oct موسوم
ordered
سل امن
wit perveptud orderiagy ۱۳
سمل موه
— qu steps io dota porrespoud to equi steps ia perceived
عل موص
Ratio data
— ‘Dero poidt disttocuishuble it oolour sequewe
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صرق
* Dugoitude oP اون ot every spoil positive
- ما بو (gray soe) or sctucatiza
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صفحه 34:
)۳۵۵
© Perceptud Rue-Bused @rchitevture Por
© Pant vf 100s Oisvatizatiod Data Cxplbrer (
* @rouides choices Por colour wups based oa
هم Prequeuy, data 1/۳, ۱
امه و (structure-preservicny),
SEyoeutativa, hichtcfsticc
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)۳۵۵
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fie Elk Cte, into سل ۱ اه یت Heb
ایدم هه 2۶ اخعز (عاس. آصاطات رد
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صفحه 37:
Fle EAL Crete demain Oper Tales iw Widow Hee
اه تكاسلا اهلف عع اضغ لعافلة إقاهاق عله
15 1.2.840.113619.2.5.1762880271.--380.1034174039.129-1
صفحه 38:
5
Fle EAL Crete demain Oper Tales iw Widow Hee
اه تكاسلا اهلف عع اضغ لعافلة إقاهاق عله
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Fie pes
الق > |
Colour
CPSC 533C
February 3, 2003
Rod McFarland
Ware, Chapter 4
•
•
•
•
The science of colour vision
Colour measurement systems and standards
Opponent process theory
Applications
The science of colour vision
• Receptors and
trichromacy theory
Red
Blue
n
ee
r
G
Colour measurement systems and
standards
• Any colour can be matched using a combination of
three “primaries”.
C rR gG bB
• The primaries are not necessarily red, green, and
blue. Any three different colours can be used. The
range of colours that can be produced from a given set
of primaries is the gamut.
Colour standards
• CIE (Commission
Internationale d’Éclairage)
– Primaries chosen for
mathematical properties: do not
actually correspond to colours.
These “virtual” colours X, Y,
and Z are called tristimulus
values.
– Y is the same as luminance
CIE – Chromaticity
• Chromaticity is derived
from tristimulus values:
• Since x+y+z=1, just use
x, y values and luminance
(Y).
• Chromaticity diagram:
x
X
1
y
Y
X Y Z
z
Z
Uniform Colour Space - CIEluv
• Uniform colour space: a
representation where equal
distances in space correspond to
equal distances in perception
• Useful for:
– Specification of colour tolerances
– Color coding (maximum distinction)
– Pseudocolour sequences to
represent ordered data values
• CIE XYZ color space is not
uniform
• CIEluv is a transformation of the
chromaticity diagram
• CIEluv does not solve all problems:
– Contrast effects
– Small colour patches: difficult to distinguish colours in
the yellow-blue direction
Opponent process theory
• Black-white (luminance), redgreen, and blue-yellow opponents
• Has basis in biology and culture
• Should use opponent colours for
coding data
Properties of Colour Channels
• Isoluminant / Equiluminous patterns: a colour
pattern whose components do not differ in
luminance
• Red-green and yellow-blue channels carry only
about 1/3 of the detail carried by black-white.
Yellow Text on a Blue Background
• Is fairly easy to read unless the text is isoluminant
with the background colour. As the luminance of
the background becomes the same as the
luminance of the text, it is very difficult to make
out what the text says. So much so, that at this
point I can write just about anything I want here
and hardly anyone would want to put in the effort
to see what it was I had written.
Other isoluminance effects
• Stereoscopic depth is not detectable with
isoluminant colours
• Isoluminance in animation makes it appear to be
slower than the same animation in black-andwhite
• Shape and form are best shown using
luminance:
Colour appearance
• Contrast
• Saturation
• Brown
low
high
Applications
• Colour selection interfaces
• Colour naming
– Natural Colour System (NCS) e.g. 0030-G80Y20
• Blackness 00, intensity 30, green 80, yellow 20
– Pantone, Munsell: standard colour chips
Applications
• Colour for labelling (nominal information
encoding)
– Distinctness
• A rapidly distinguished colour lies outside the convex
polygon defined by the other colours in CIE space
Applications
• Colour for labelling (2)
– Unique hues: “universally recognized” hues (red,
green, blue, yellow, black, white) should be used
– Contrast with background: border around objects
Applications
• Colour for labelling (3)
– Colour blindness: majority of colour-blind people
cannot distinguish red-green, but most people can
distinguish blue-yellow
– Number: only 5-10 codes easily distinguished
Applications
• Colour for labelling (4)
– Size
• Colour-coded objects should not be very small (about ½
degree minimum size).
• Smaller objects should be more highly saturated, large
colour-coded regions should have low saturation. Text
highlighting should be high-luminance, low-saturation.
– Conventions
• Common usage of colours, e.g. red=stop, green=ready,
blue=cold…
Applications
• Colour for labelling (5)
– Ware’s 12 recommended colours (in order of
preference):
Applications
• Pseudocolour sequences for mapping
– Pseudocolouring is the practice of assigning colour to
map values that do not represent colour
• Medical imaging
• Astronomical images
• Mapping nonvisible spectrum information to the visible
spectrum (astronomy, infrared images)
– Gray scale best for showing surface shape
– Colour best for classification
Applications
• Colour for mapping (2)
– For orderable sequences, black-white, red-green, blueyellow, or saturation (dull-vivid) sequence can be used.
– For detailed data, the sequence should be based mainly on
luminance. For low letail, chromatic or saturation sequences
can be used.
– Uniform colour spaces can be used to create colour
sequences where equal perceptual steps correspond to equal
metric steps.
– Where it is important to be able to read off values from a
colour map, a sequence that cycles through many colours is
preferable.
Applications
• Colour for mapping (3)
– A “spiral” through colour space (cycling through
several colours while continuously increasing in
luminance) is often a good choice.
Hue 0, 50,…250, 45, 95…
Luminance 0, 25, 50… 225
Applications
• Colour for mapping (4)
– Perception: even if the sequence is smooth, people
tend to see discrete colours, potentially miscategorizing
data.
• My personal division into blue, green, yellow, orange, red,
purple: very nonlinear
Applications
• Colour for mapping (5)
– Using colour for 3-D information mapping
• Difficult to read accurately
• May be used to identify regions
• Satellite images: regions of invisible spectrum mapped to
red, green, blue channels
Applications
• Colour for multidimensional discrete data
– 5-D plot using (x, y) position, red, green, blue
– Possible to identify clusters
– Ambiguous: is a point low-red or high-green?
– Other methods needed to analyze clusters once
identified
Rogowitz et al.
How Not to Lie with Visualization
• Visual representation of data affects the perceived
structure of the data.
Enhancing data interpretation
Colour
using
• Perceptual impact of a colour is not predictable from the
red/green/blue components of the colour
• Mapping different aspects of colour to different data is
not intuitively decodable by users.
• Default colour maps: rainbow
– Perceptual nonlinearity
– False contours
– Yellow attracts attention
Guiding colour map selection
• Constrain the set of colour maps available to the
user based on:
– Data type
– Data spatial frequency
– Visualization task
– Other design choices made by user
Representing Structure
• Nominal data
– Object should be distinguishably different but not perceptually
ordered
• Ordinal data
– Distinguishable with perceptual ordering
• Interval data
– Equal steps in data correspond to equal steps in perceived
magnitude
• Ratio data
– Zero point distinguishable in colour sequence
Structure
• Magnitude of a variable at every spatial position
– Use luminance (gray scale) or saturation
high
spatial frequency
low
Spatial Frequency
luminance-based
saturation-based
Segmentation
• Low frequency – more segmentation steps can be used
Highlighting
Luminance-based map can be
highlighted using hue variations. The
highlighted regions have the same
luminance value as the rest of the
map.
PRAVDA
• Perceptual Rule-Based Architecture for
Visualizing Data Accurately
• Part of IBM’s Visualization Data Explorer (
http://www.research.ibm.com/dx/)
• Provides choices for colour maps based on
spatial frequency, data type, and user-selected
goal: isomorphic (structure-preserving),
segmentation, highlighting
PRAVDA