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Use of Java for Demonstration
of Color Science Concepts
Presentation of an MS Project, submitted to The
Faculty of the Computer Science Department, in
partial fulfillment of the requirements for the
degree of Master of Science in Computer Science
from Rochester Institute of Technology
John A. Moore
April 29, 1998
Project Objectives
• Gain knowledge and experience with Java
Programming.
• Apply my knowledge of Color Science.
• Generate a Package of general purpose
Color Science Java classes for others to
use and grow.
• Complete requirements for MS Degree.
Why Java ?
• Java is rich in it’s support of imaging
and color.
• Demonstrations can (easily) be shared
on the web
• Inherent portability to different
platforms and hardware.
Development Environment
• Experimented with many…
– Microsoft Visual J++
– Semantics Visual Café for Java
– Basic JDK
• Settled on JpadPro
–
–
–
–
Basic project management
Support for custom Packages
Colored coded text editor
Easy to use and learn
JpadPro
http://www.modelworks.com
Color Science Fundamentals
Additive Color Mixing
Subtractive Color Mixing
The Java Demonstrations
Three Color Science Demonstrations
Simple Subtractive Color Mixing
Simple Additive Color Mixing
Calculation of Helmholtz coordinates
Simple Subtractive Color Mixing
Features & Functions
• Double Buffered imaging to avoid
flicker
• Back-light switch to emphasize
subtraction of light.
• System requirements check.
• Instruction panel
Show Subtractive Color
Mixing Applet
Additive Color Mixing
Features & Functions
• Allows user to choose color of each
primary
• Select a color ‘mixture’ from a color
picker
• Allows the user to see the selected
color in a mixer panel.
• Utilizes a ‘super cell’ technique
Primary Components
Super Pixel Concept
Monitor Pixel
p1
p2
p3
p3
p1
p2
p2
p3
p1
Super pixel
p1 = primary 1
p2 = primary 2
p3 = primary 3
• Allows full RGB control over each “Primary”
• More pleasing at 45 degree angle
Color Picker Space
Implementation
RadialCenter
P1
P2
P1
30
RadialMax
Width
P3
Where:
RadialMax = ( Width / 2 ) / Tan 30
RadialCenter = (Width / 2 ) / Cos 30
Illustration of intensity
variation for P1 only
Show Additive mixing
demonstration
Class Hierarchy
for Additive Color Mixing
coloRama
AdditiveMixerPanel
GamutPanel
gammutScreen
Primary
ShowMixPanel
colorPickerPanel
PrimaryDisplay
ThreeSliderControl
Three things to perceive color
Object
Eye
Source
But how do you specify color….
Color Matching Experiments
237
224
103
r, g, b Color Matching Function
Wavelength ()
Transformed to x, y, z
CIE 1931 Standard observer
• To avoid negative numbers and simplify calculations
• set y to equal the spectral luminous efficiency fnct
(corresponding to a color’s lightness)
Three things to perceive color
300 400 500 600 700
Source
Object
300 400 500 600 700
Eye
Calculation of Tristimulus Values
X = k
PRx
Y = k
PRy
Z = k
PRz
100
Where: k =
Py
And P = relative power distribution of CIE standard illuminant
R = spectral reflectance of the object
Chromaticity Coordinates
• Translate the X, Y, Z to two
dimensions for convenience
x =
X
X+Y+Z
y =
Y
X+Y+Z
• Only need two points since:
z =
Z
X+Y+Z
x + y + z = 1.0
Chromaticity Diagram
The Helmholtz Demonstration
• Helmholtz coordinates are an
alternative way to expressing
chromaticity values.
But what are they…...
Calculation of Helmholtz coordinates
0.8
0.6
x
0.4
Select a
White Point
0.2
0
0
0.2
0.4
y
0.6
Calculation of Helmholtz coordinates
0.8
0.6
x
Select a
Sample Point
0.4
0.2
0
0
0.2
0.4
y
0.6
Calculation of Helmholtz coordinates
0.8
Next…
Draw a Line
through the
White point
and sample
point
0.6
x
0.4
0.2
0
0
0.2
0.4
y
0.6
Calculation of Helmholtz coordinates
0.8
The “Dominant
Wavelength”
is determined by
the intersection
with the
spectrum Locus.
0.6
x
0.4
0.2
0
0
0.2
0.4
y
0.6
Calculation of Helmholtz coordinates
...and the
“excitation Purity”
is determined by
the ratio of the
distances as shown.
0.8
0.6
B
x
A
0.4
such that
Pe = A/B
0.2
0
0
0.2
0.4
y
0.6
Complimentary Wavelength
Algorithm
The condition shown in yellow is met when...
• The slope of the line is positive.
• The y-value of the line at x is less than the y-value of the
locus at x.
• The sample point x-chroma value is greater than the
White Point x-chroma value OR Sample point is a
Complimentary Color...
The condition shown in green is met when…
• The slope of the line is positive.
• The y-value of the line at x is greater than the y-value of
the locus at x.
• Sample point x-chroma value is less than the White Point
x-chroma value AND The sample point is not a
Complimentary Color.
The condition shown in blue is met when...
• The slope of the line is negative.
• The y-value of the line at x is greater than the y-value of
the locus at x.
• Sample point x-chroma value is less than the White Point
x-chroma value OR The Sample point is a Complimentary
Color...
The condition shown in pale red is met when...
• The slope of the line is negative.
• The y-value of the line at x is less than the y-value of the
locus at x.
• Sample point x-chroma value is greater than the White
Point x-chroma value AND The Sample point is not a
Complimentary Color...
Show
Helmholtz Application
Class Hierarchy
for Additive Color Mixing
Helmholtz
helmholtzPanel
chromaticityControls
chromaticityPanel
illuminantPanel
colorSamplePanel
ChromaValuesPanel
ChromaValuesPanel
feedBackPanel
feedBackPanel
whitePointDataClass
Color_kit Package
color_kit.color_space
color_kit.color_space.uv_chromaticity
color_kit.color_space.xy_10degree_chromaticity
color_kit.color_space.xy_chromaticity
color_kit.dialogs
color_kit.panels
color_kit.panels.bundles
color_kit.panels.controls
color_kit.panels.displays
color_kit.toolkit
Discussion of Results
• Numerous Java VM inconsistencies
–Sun JDK, MS SDK, Netscape (Semantics)
• Wide performance variations
• Java 1.1.5 VM roll-out
Conclusion
• Future Work
• Acknowledgements