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In this paper, we propose a fast re-coloring algorithm to improve the accessibility for the color vision impaired. Compared to people with normal color vision, people with color vision impairment have difficulty in distinguishing between certain combinations of colors. This may hinder visual communication owing to the increasing use of colors in recent years. To address this problem, we re-map the hue components in the HSV color space based on the statistics of local characteristics of the original color image. We enhance the color contrast through generalized histogram equalization. A control parameter is provided for various users to specify the degree of enhancement to meet their needs. Experimental results are illustrated to demonstrate the effectiveness and efficiency of the proposed re-coloring algorithm.
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Enhancing Color Representation for the ColorVision Impaired
Jia-Bin Huang1, Sih-Ying Wu2, and Chu-Song Chen1
jbhuang@iis.sinica.edu.tw
1 Institute of Information ScienceAcademia Sinica
2Department of Electronics EngineeringNational Chiao Tung University
October 18, 2008
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Outline
1 IntroductionColor Vision Deficiency (CVD)Related Works
2 The Proposed AlgorithmMain IdeaGeneralized Histogram EqualizationControlling the Enhancement Degree
3 Results and DiscussionVisual ResultsInteractive InterfaceApplications
4 Conclusion
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Outline
1 IntroductionColor Vision Deficiency (CVD)Related Works
2 The Proposed AlgorithmMain IdeaGeneralized Histogram EqualizationControlling the Enhancement Degree
3 Results and DiscussionVisual ResultsInteractive InterfaceApplications
4 Conclusion
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Color Vision
Normal visionThree different fundamental photoreceptor cells (cone cells)Peak responses lie in long (L), middle (M), and short (S)wavelength regions
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Classification of CVD
Anomalous trichromacyOne of the three cone cells is abnormal
DichromacyOne of the three cone cells is absent
MonochromacyAll three cone cells are absent
Table: Major genetic color deficiencies.
Type Name Cause of defect
Anomalous trichromacyProtanomaly L-cone defectDeuteranomaly M-cone defectTritanomaly S-cone defect
DichromacyProtanopia L-cone absentDeuteranopia M-cone absentTritanopia S-cone absent
Monochromacy Rod Monochromacy no functioning cones
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
How People with CVD perceive Colors?
Anomalous trichromacy
Protanomaly Deuteranomaly TritanomalyDichromacy
Protanopia Deuteranopia TritanopiaJia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Related Works
1 Guideline or assistant tool for designers to avoidambiguous color combinations
Provide guideline (Chisholm et al. 01)Use a restricted CVD palette (Rigden et al. 99, Vienot99 etal. 99)Verify color schemes (Walraven et al.97, Jenny07 et al. 07)
2 (Semi-)automatically reproduce colors that are suitable forCVD viewers
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Related Works
1 Guideline or assistant tool for designers to avoidambiguous color combinations
Provide guideline (Chisholm et al. 01)Use a restricted CVD palette (Rigden et al. 99, Vienot99 etal. 99)Verify color schemes (Walraven et al.97, Jenny07 et al. 07)
2 (Semi-)automatically reproduce colors that are suitable forCVD viewers
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Related Works
1 Guideline or assistant tool for designers to avoidambiguous color combinations
Provide guideline (Chisholm et al. 01)Use a restricted CVD palette (Rigden et al. 99, Vienot99 etal. 99)Verify color schemes (Walraven et al.97, Jenny07 et al. 07)
2 (Semi-)automatically reproduce colors that are suitable forCVD viewers
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Typical Re-coloring Approaches
Common procedures
Select key colors using color quantization
Find the optimal mapping of key colors using optimizationprocedure
Obtain the re-colored image through interpolation
(Ichikawa et al. 04, Wakita et al. 05, Rasche et al. 05,JeRerson et al. 06, Huang et al. 07)Drawbacks:
Slow. Require a few minutes for an image
Problem of gamut mapping, illumination inconsistency.
Unnatural color for the colorblind
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Typical Re-coloring Approaches
Common procedures
Select key colors using color quantization
Find the optimal mapping of key colors using optimizationprocedure
Obtain the re-colored image through interpolation
(Ichikawa et al. 04, Wakita et al. 05, Rasche et al. 05,JeRerson et al. 06, Huang et al. 07)Drawbacks:
Slow. Require a few minutes for an image
Problem of gamut mapping, illumination inconsistency.
Unnatural color for the colorblind
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Typical Re-coloring Approaches
Common procedures
Select key colors using color quantization
Find the optimal mapping of key colors using optimizationprocedure
Obtain the re-colored image through interpolation
(Ichikawa et al. 04, Wakita et al. 05, Rasche et al. 05,JeRerson et al. 06, Huang et al. 07)Drawbacks:
Slow. Require a few minutes for an image
Problem of gamut mapping, illumination inconsistency.
Unnatural color for the colorblind
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Typical Re-coloring Approaches
Common procedures
Select key colors using color quantization
Find the optimal mapping of key colors using optimizationprocedure
Obtain the re-colored image through interpolation
(Ichikawa et al. 04, Wakita et al. 05, Rasche et al. 05,JeRerson et al. 06, Huang et al. 07)Drawbacks:
Slow. Require a few minutes for an image
Problem of gamut mapping, illumination inconsistency.
Unnatural color for the colorblind
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Outline
1 IntroductionColor Vision Deficiency (CVD)Related Works
2 The Proposed AlgorithmMain IdeaGeneralized Histogram EqualizationControlling the Enhancement Degree
3 Results and DiscussionVisual ResultsInteractive InterfaceApplications
4 Conclusion
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Main Idea
Main Idea
Maintain luminance and saturation consistency.=>Work in the HSV color space, and leave value andsaturation component unchanged
Preserve the natural order of hue.=>Apply a hue transfer function to hue channel(non-decreasing)
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Contrast Enhancement using Histogram Equalization(HE)
One of the most well-known technique for imageenhancement
Assign larger dynamic range for intensity values havinglarger number of occurrences
T(g) = gmin + (gmax − gmin)
∫g
gmin
hist(g) dg
T(g): Intensity mapping function
hist(g): Normalized histogram (probability distribution ofthe grey levels in the image)
gmax, gmin: Maximum and minimum intensity values
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Histogram Generalization
Original Histogram
Histogram generationMasking-and-accumulating using 1 × 1 block
Generalized Histogram
Generalized histogramExtend 1 × 1 block to N × N to encode spatial informationReplace sampling by measurement(feature extraction)
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Three Local Measurement
1 Hue value at point (x, y)
α(x, y) = hue(x, y)
2 Local hue difference
β(x, y) = maxi,j
{hue(i, j)} − mini,j
{hue(i, j)}, (i, j) ∈ N(x, y)
3 Color confusability due to CVD
γ(x, y) =∑
(i,j)∈N(x,y)
(||(C(x, y) − C(i, j))||−
||(Sim(C(x, y)) − Sim(C(i, j)))||)2
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Three Local Measurement
1 Hue value at point (x, y)
α(x, y) = hue(x, y)
2 Local hue difference
β(x, y) = maxi,j
{hue(i, j)} − mini,j
{hue(i, j)}, (i, j) ∈ N(x, y)
3 Color confusability due to CVD
γ(x, y) =∑
(i,j)∈N(x,y)
(||(C(x, y) − C(i, j))||−
||(Sim(C(x, y)) − Sim(C(i, j)))||)2
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Three Local Measurement
1 Hue value at point (x, y)
α(x, y) = hue(x, y)
2 Local hue difference
β(x, y) = maxi,j
{hue(i, j)} − mini,j
{hue(i, j)}, (i, j) ∈ N(x, y)
3 Color confusability due to CVD
γ(x, y) =∑
(i,j)∈N(x,y)
(||(C(x, y) − C(i, j))||−
||(Sim(C(x, y)) − Sim(C(i, j)))||)2
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Color Confusability Map
γ(x, y) =∑
(i,j)∈N(x,y)
(||(C(x, y) − C(i, j))||−
||(Sim(C(x, y)) − Sim(C(i, j)))||)2
1 The value of γ(x, y) in logarithmic scale
(a) (b) (c)
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Combining Three Measurement
α: hue value
β: local hue difference
γ: local color confusability
Conventional histogram accumulating function
δ(h − α)
Generalized histogram accumulating function
S(h|α,β, γ) = γ × Rect(h − α
β)
Rect(x) ≡
{
1, if − 0.5 ≤ x ≤ 0.5,0, otherwise.
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Generalized Histogram Equalization
By scanning over the whole image, the generalizedhistogram can be obtained:
GH(h) =
∫ ∫
S(h|α(x, y), β(x, y), γ(x, y))dxdy
Construct the hue transfer function
T(h) = hmin + (hmax − hmin)
∫h
hmin
GH(h)dh
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Controlling the Enhancement Degree
Add a magnitude mapping function
M(x) = xp
The hue transfer function
T(h) = hmin + (hmax − hmin)
∫h
hminM(GH(h))dh
∫hmax
hminM(GH(h))dh
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Outline
1 IntroductionColor Vision Deficiency (CVD)Related Works
2 The Proposed AlgorithmMain IdeaGeneralized Histogram EqualizationControlling the Enhancement Degree
3 Results and DiscussionVisual ResultsInteractive InterfaceApplications
4 Conclusion
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Visual Results
Ishihara test chart
(a) (c) (e) (g)
(b) (d) (f) (h)
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Comparison with Rasche et al’s Approach
Image Simulation Our results Rasche et al’s results
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Comparison with Jeferson et al.’s Approach (1/2)
Image Our results Jeferson et al.’s results
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Comparison with Jeferson et al.’s Approach (2/2)
Image Our results Jeferson et al.’s results
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Controlling the Enhancement Degree
(a) (c)p = 0.2 (e)p = 0.6 (g)p = 1.0
(b)p = 0 (d)p = 0.4 (f)p = 0.8 (h)p = 1.2
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Controlling the Enhancement Degree
(a) (c)p = 0.2 (e)p = 0.6 (g)p = 1.0
(b)p = 0 (d)p = 0.4 (f)p = 0.8 (h)p = 1.2
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Applications
Improve web accessibility for the colorblind
Color adaptation in multimedia content (e.g. images,videos etc.)
Assistive technologies for designers
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Outline
1 IntroductionColor Vision Deficiency (CVD)Related Works
2 The Proposed AlgorithmMain IdeaGeneralized Histogram EqualizationControlling the Enhancement Degree
3 Results and DiscussionVisual ResultsInteractive InterfaceApplications
4 Conclusion
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
Conclusion and Future Work
ConclusionFast re-color algorithm for CVD viewersRe-color image using local contrast informationInteractive interface
Future workSubjective experimentsRe-coloring through optimization
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
The End
Thank you
Jia-Bin Huang et al. (IIS, Academia Sinica) Enhancing Color Representation for the Color Vision Impaired
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