The document discusses color perception and hue histograms. It begins by showing an image and asking the reader about their perception of the colors. It then demonstrates how histograms of hue can provide insight into the distribution of colors in an image compared to looking at RGB channel histograms. Different methods for constructing hue histograms are presented, including simple frequency, weighted by saturation, and Gaussian weighting. The document argues that hue histograms can help improve color perception compared to RGB channels alone.

1. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
About Perception and HueAbout Perception and Hue
Histograms in HSV SpaceHistograms in HSV Space
Michel Alves dos Santos
May, 2015
*original
*hue-saturation projection
*saturation
*brightness
*hue histogram

2. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
IntroductionIntroduction
red channel green channel blue channel
What's your perception about
the colors of this image?
*Barns Grand Teton: Grand Teton National Park
Note the marked areas!
And the distribution by channel?
How each color component behaves in its proper channel?

3. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
IntroductionIntroduction*Barns Grand Teton: Grand Teton National Park
Observe the distribution of
energy for each channel:
But, about the hues? What the RGB model can tell us?
This kind of graph shows us how the energy of each channel is distributed!
red channel green channel blue channel

4. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
IntroductionIntroduction*Barns Grand Teton: Grand Teton National Park
Firstly, we will use the HSV Color Space ...
How to build a hue histogram?
Now, note the diagram below:
Can you identify hues distinctly?
Probably not! Because of clusters
and the intersection of colors!
A histogram of hues can help us
improve our perception!

5. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Spaces)(Color Spaces)
RGB Color Space HSV Color Space
*Solids produced using POV­Ray [http://lib.povray.org/]
Simplicity in representation and storage Close to human perception
Some point operations are faster... Easy interpolation between colors
Invariant to illumination transformsHave lighting and color properties togetherHave lighting and color properties together

6. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Spaces – a common mistake...)(Color Spaces – a common mistake...)
RGB Color Space HSV Color Space
*Solids produced using POV­Ray [http://lib.povray.org/]
A cone is commonly adopted but cylindrical
representation is more mathematically accurate.

7. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Spaces – Solids Transition)(Color Spaces – Solids Transition)
RGB Color Space HSV Color Space
*Solids produced using POV­Ray [http://lib.povray.org/]

8. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Transformation)(Transformation)
RGB HSV Transformation
isn't linear!
Some care should be taken
with monochromatic
pixels!
*[avoid divisions by zero]

9. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Transformation)(Transformation)
RGB HSV Transformation
isn't linear!
Alternative
Some care should be taken
with monochromatic
pixels!
*[avoid divisions by zero]

10. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Image Thresholding)(Color Image Thresholding)
Find the yellow M&M's!
A simple task for a human
observer, but not so easy
for machines:
Complexity depends of the space!
Using RGB:
R:
G:
B:
200 255
200 255
0 50
Using HSV:(3 intervals) (1 interval)

11. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Image Thresholding)(Color Image Thresholding)
Find the yellow M&M's!
A simple task for a human
observer, but not so easy
for machines:
Complexity depends of the space!
Using RGB:
R:
G:
B:
200 255
200 255
0 50
Using HSV:(3 intervals) (1 interval)
[This approach is independent of saturation or brightness]

12. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
*Barns Grand Teton: Grand Teton National Park
RGB Vs HSVRGB Vs HSV (Color Image Thresholding)(Color Image Thresholding)
*hues of sky *hues of barn *hues of grass
Using this feature some tasks
can be easily performed!
As detection of regions or objects
by its characteristic colors!
It's one of the bases of color perception!

13. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Perception)(Color Perception)
And now, what's your perception
about the colors of this image?
*Barns Grand Teton: Grand Teton National Park
Where we have more blue hues?
Where we have more orange hues?
Where we have more green hues?
Here we have a blend of yellow and green hues!
Do not fool yourself!
(Grass???)
(Sky)
(Barn)
*hue histogram
*hue projection

14. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Color Perception)(Color Perception)
And now, what's your perception
about the colors of this image?
*Barns Grand Teton: Grand Teton National Park
Where we have more blue hues?
Where we have more orange hues?
Where we have more green hues?
Here we have a blend of yellow and green hues!
Do not fool yourself!
(Grass???)
(Sky)
(Barn)
*hue histogram
*hue projection

15. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
RGB Vs HSVRGB Vs HSV (Meanings of the Components)(Meanings of the Components)
Energy of red channel Energy of green channel Energy of blue channel
What is the basic color? How vibrant is the color? How brightness is the color?

16. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue HistogramsHue Histograms
*hue projection *saturation *value
We will build our histograms taking
account the number of positions
of the hue circle!
Number of bins (discrete positions): 0..360 or 0 to 2π
Note that the hue channel is a ring structure!

17. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms - StepsHue Histograms - Steps
Our input images are in RGB Color Space, the output is a transformed hue histogram...
We are applying a square root transformation to obtain the final hue histogram...
Observe the follow
diagram!
The metric of contribution is a flexible part of the process and depends of application...

18. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms - StepsHue Histograms - Steps
Our input images are in RGB Color Space, the output is a transformed hue histogram...
We are applying a square root transformation to obtain the final hue histogram...
Observe the follow
diagram!
The metric of contribution is a flexible part of the process and depends of application...
Get to work!
Now, I will show
some metrics!

19. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: Simple FrequencyHue Histograms :: Simple Frequency*Barns Grand Teton: Grand Teton National Park
Kronecker Delta
Hue
Picture or Image
*hue histogram
This is a simple counting!
It doesn't consider other
HSV channels.
Bin Position
PixelHistogram
Notation

20. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: by SaturationHue Histograms :: by Saturation*Barns Grand Teton: Grand Teton National Park
*hue histogram
Kronecker Delta
Hue
Picture
Only considers the
saturation channel...
Saturation
Ref: [LP'15]
Bin Position
PixelHistogram

21. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: by ContributionHue Histograms :: by Contribution*Barns Grand Teton: Grand Teton National Park
*hue histogram
Kronecker DeltaSaturation ValuePicture
Hue
Histogram Pixel
Bin Position

22. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Weighted by ContributionWeighted by Contribution
*Barns Grand Teton: Grand Teton National Park
*hue histogram
Kronecker DeltaSaturation ValuePicture
Hue
*similar to the previous!
Normalization Factor
Bin Position
Pixel

23. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: Hasan WeightedHue Histograms :: Hasan Weighted Ref: [MAH'12]
*hue histogram
*Barns Grand Teton: Grand Teton National Park
Picture Previous Histogram
*exponential weighted histogram
Mean of Hues
*similar to the previous???
Mean
Variance
Variance of Hues
Notation
Weighted Histogram
Bin Position

24. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: Hasan WeightedHue Histograms :: Hasan Weighted Ref: [MAH'12]
*hue histogram
*Barns Grand Teton: Grand Teton National Park
Picture Previous Histogram
*exponential weighted histogram
Mean of Hues
*similar to the previous???
Variance of Hues *before weighting *after weighting
frequency frequencyhue hue
Weighted Histogram
Bin Position

25. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: Gaussian WeightedHue Histograms :: Gaussian Weighted
Gaussian Function
*Barns Grand Teton: Grand Teton National Park
*hue histogram
Picture Previous Histogram
Weighted Histogram
Bin Position
Mean of Hues
Variance of Hues

26. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Smoothed by BoxSmoothed by Box
*hue histogram, window size = 1x9
*Barns Grand Teton: Grand Teton National Park
Box function
Convolution
Gaussian Function
Previous HistogramWeighted Histogram

27. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Smoothed by BoxSmoothed by Box
*hue histogram, window size = 1x9
*Barns Grand Teton: Grand Teton National Park
Box function
Convolution
Gaussian Function
Previous HistogramWeighted Histogram
*smoothing employing a boxcar function

28. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Smoothed by GaussianSmoothed by Gaussian
*hue histogram, window size = 1x9
*Barns Grand Teton: Grand Teton National Park
Gaussian function
Convolution
Gaussian Function
Previous HistogramWeighted Histogram

29. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Smoothed by a KernelSmoothed by a Kernel
*hue histogram, window size = 1x11
*Barns Grand Teton: Grand Teton National Park
kernel
Kernel function
Convolution
Gaussian Function
Previous HistogramWeighted Histogram

30. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Smoothed by a KernelSmoothed by a Kernel
*hue histogram, window size = 1x11
*Barns Grand Teton: Grand Teton National Park
kernel function employed: Epanechnikov
kernel
Kernel function
Convolution
Gaussian Function
Previous HistogramWeighted Histogram

31. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Spatial Color CoherenceSpatial Color Coherence
*hue histogram, window size = 1x11
*Barns Grand Teton: Grand Teton National Park
kernel
Spatial Color Coherence Neighborhood Difference
Kernel functionConvolution
*8-connected neighborhood
Gaussian FunctionWeighted Histogram Saturation Value Kronecker Delta

32. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms ::Hue Histograms :: Spatial Color CoherenceSpatial Color Coherence
*hue histogram, window size = 1x11
*Barns Grand Teton: Grand Teton National Park
kernel
Spatial Color Coherence Neighborhood Difference
Kernel functionConvolution
*8-connected neighborhood
Gaussian FunctionWeighted Histogram Saturation Value Kronecker Delta
*Spatial Color Coherence Map

33. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Hue Histograms :: The end of our jorney...Hue Histograms :: The end of our jorney...
Simple Frequency
By Contribution
Weighted Contribution
Hasan Weighted
By Saturation
Gaussian WeightedSmoothed
A brief visualA brief visual
comparison!comparison!
This is the end!

34. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
ConclusionConclusion
Use the appropriate space for your problem! Always!
Hue based histograms can be employed in a wide range of applications!
Color spaces that have hue separation approximate human perception!
Some considerations should be taken into account in the construction of a hue
histogram as brightness and perceptive contribution...

35. Federal University of Rio de Janeiro (UFRJ) :: Campus Cidade Universitária :: Rio de Janeiro :: Fundão Island :: COPPE/PESC/Laboratory of Computer Graphics :: March/2015
Michel Alves -- Five Minute Speech (FMS) :: Overview of Activities Developed in Disciplines and Guided Studies :: Graduate Program in Systems Engineering and Computing
Thanks for your attention!Thanks for your attention!
Michel Alves dos SantosMichel Alves dos Santos
References:References:
Digital Image Processing (3rd Ed), Gonzalez & Woods, Pages 407-437. [GW'08]
Blind Stain Decomposition for Histo-Pathology Images Using Circular Nature
of Chroma Components, Li & Plataniotis, 2015, Page 2. [LP'15]
Color Image Segmentation Using Acceptable Histogram Segmentation, Delon
et al., 2005, LNCS.
Shot Classification Using Domain Specific Features for Movie Management,
Hasan et al., 2012, LNCS, Springer. [MAH'12]
Contrast Enhancement of Color Images Based on Wavelet Transform and
Human Visual System, 2007, Xiao & Ohya, IASTED.
Progressive Histogram Reshaping for Creative Color Transfer and Tone
Reproduction, Pouli & Reinhard, 2010, NPAR2010.