Talk given at APIS 2008

1. Motivation Colour Capturing Colour Management Solution Summary
Gaining Colour Stability
in Live Image Capturing
Guy K. Kloss
Computer Science
Massey University, Albany
International Conference on
Applications and Principles of Information Science
29 January 2008
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 1/30

2. Motivation Colour Capturing Colour Management Solution Summary
Outline
1 Motivation
2 Colour Capturing
3 Colour Management
4 Solution
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 2/30

3. Motivation Colour Capturing Colour Management Solution Summary
Outline
1 Motivation
2 Colour Capturing
3 Colour Management
4 Solution
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 3/30

4. Motivation Colour Capturing Colour Management Solution Summary
The Basic Problem
We do not recognise light changes
Cameras do!
Colour measurements are off!
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 4/30

5. Motivation Colour Capturing Colour Management Solution Summary
The Basic Problem
We do not recognise light changes
Cameras do!
Colour measurements are off!
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 4/30

10. Motivation Colour Capturing Colour Management Solution Summary
The Basic Problem
Anticipated Solution
Create a system
that is able to adapt to the conditions automatically.
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 9/30

11. Motivation Colour Capturing Colour Management Solution Summary
Outline
1 Motivation
2 Colour Capturing
3 Colour Management
4 Solution
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 10/30

12. Motivation Colour Capturing Colour Management Solution Summary
(Human) Colour Sensing
Reflection Model
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 11/30

13. Motivation Colour Capturing Colour Management Solution Summary
(Human) Colour Sensing
Spectral Light Composition
relative spectral power
Light Source D65
F2
400 450 500 550 600 650 700
wavelength λ [nm]
Object
relative reflectance
400 450 500 550 600 650 700
wavelength λ [nm]
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 12/30

14. Motivation Colour Capturing Colour Management Solution Summary
(Human) Colour Sensing
Spectral Light Composition
S M L
relative sensitivity
S M L
400 450 500 550 600 650 700
wavelength λ [nm]
B G R
relative sensitivity
400 450 500 550 600 650 700
wavelength λ [nm]
Relative sensitivities of cone cells (spectrum top). Typical camera sensors (spectrum bottom).
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 13/30

15. Motivation Colour Capturing Colour Management Solution Summary
Colour Capturing
Werner Heisenberg, Physics and Philosophy (1958)
“What we observe is not nature itself,
but nature exposed to our method of questioning.”
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 14/30

16. Motivation Colour Capturing Colour Management Solution Summary
Colour Capturing
Capturing Process
Sensing
Rendering
Encoding
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 15/30

17. Motivation Colour Capturing Colour Management Solution Summary
Colour Capturing
Problems
Sensor readings are not passed through,
they are “interpreted!”
Measurement dependent on . . .
Illuminant
Surface Colour
Camera
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 16/30

18. Motivation Colour Capturing Colour Management Solution Summary
Colour Spaces
Lost in Colour Space?
RGB, sRGB, Adobe RGB, . . .
YUV
HLS, HSV
CMYK
YCrCb
XYZ
CIE LAB, CIE LUV
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 17/30

19. Motivation Colour Capturing Colour Management Solution Summary
Colour Spaces
Crash-Course in Sensible Colour Spaces
RGB != RGB
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 18/30

20. Motivation Colour Capturing Colour Management Solution Summary
Colour Spaces
Categorisation
Dependency
Device dependent
Device independent
Linearity
physical (with intensity)
physical (for a specific output device)
visual (CIE LAB)
Number of Channels
Here: Building a system based on visible colours
(trichromatic colour spaces)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 19/30

21. Motivation Colour Capturing Colour Management Solution Summary
Colour Spaces
Categorisation
Dependency
Device dependent
Device independent
Linearity
physical (with intensity)
physical (for a specific output device)
visual (CIE LAB)
Number of Channels
Here: Building a system based on visible colours
(trichromatic colour spaces)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 19/30

22. Motivation Colour Capturing Colour Management Solution Summary
Colour Spaces
Categorisation
Dependency
Device dependent
Device independent
Linearity
physical (with intensity)
physical (for a specific output device)
visual (CIE LAB)
Number of Channels
Here: Building a system based on visible colours
(trichromatic colour spaces)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 19/30

23. Motivation Colour Capturing Colour Management Solution Summary
Colour Spaces
CIE LAB
1976, CIE L*a*b* (and L*u*v* )
Linear (visually), Device Independent,
Opponent Colour Space
Guy K. Kloss — LAB is shown inStability in Live Image Capturing
(Only CIE Gaining Colour the diagrams.) 20/30

24. Motivation Colour Capturing Colour Management Solution Summary
Outline
1 Motivation
2 Colour Capturing
3 Colour Management
4 Solution
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 21/30

25. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
(static)
Using ICC profiles and CIE colour spaces
Independent, linear PCS
(usable for visual processing)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 22/30

26. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
(static)
Using ICC profiles and CIE colour spaces
Independent, linear PCS
(usable for visual processing)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 22/30

27. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
Input Device Calibration
Preconditions:
Colour characterisation target
Reproducible conditions (illumination)
A specific camera
1 Capturing of target
2 Comparison of measurement vs. true values
3 Computation of ICC profile (lookup table)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30

28. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
Input Device Calibration
Preconditions:
Colour characterisation target
Reproducible conditions (illumination)
A specific camera
1 Capturing of target
2 Comparison of measurement vs. true values
3 Computation of ICC profile (lookup table)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30

29. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
Input Device Calibration
Preconditions:
Colour characterisation target
Reproducible conditions (illumination)
A specific camera
1 Capturing of target
2 Comparison of measurement vs. true values
3 Computation of ICC profile (lookup table)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30

30. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
Input Device Calibration
Preconditions:
Colour characterisation target
Reproducible conditions (illumination)
A specific camera
1 Capturing of target
2 Comparison of measurement vs. true values
3 Computation of ICC profile (lookup table)
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30

31. Motivation Colour Capturing Colour Management Solution Summary
Colour Management
Problems for Live Capturing
The Problem:
This does not work in changing/live environments!
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 24/30

32. Motivation Colour Capturing Colour Management Solution Summary
Outline
1 Motivation
2 Colour Capturing
3 Colour Management
4 Solution
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 25/30

33. Motivation Colour Capturing Colour Management Solution Summary
Approaches for a Solution
Usable Clues:
A priori knowledge
Infering by image analysis
(Colour Constancy methods)
Advantage of slow changes:
Image segmentation
Observe background changes
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 26/30

34. Motivation Colour Capturing Colour Management Solution Summary
Approaches for a Solution
Usable Clues:
A priori knowledge
Infering by image analysis
(Colour Constancy methods)
Advantage of slow changes:
Image segmentation
Observe background changes
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 26/30

35. Motivation Colour Capturing Colour Management Solution Summary
Approaches for a Solution
Usable Clues:
A priori knowledge
Infering by image analysis
(Colour Constancy methods)
Advantage of slow changes:
Image segmentation
Observe background changes
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 26/30

36. Motivation Colour Capturing Colour Management Solution Summary
Putting it Together
De-coupled live process:
Processing loop with “pay load”
Adaptation process
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 27/30

37. Motivation Colour Capturing Colour Management Solution Summary
Summary
Overview in Colour Science
→ Colour Sensing/Measuring, Colour Representation
Colour Management
→ Industry Standards and Best Practices,
Static Characterisation
Dynamic/Live Solution
→ Usable Clues, Implementation
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 28/30

39. Motivation Colour Capturing Colour Management Solution Summary
Questions?
What colour is the lemon?
If you look closely, you may be surprised!
G.Kloss@massey.ac.nz
Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 30/30