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Hue-Preserving Color Blending

Johnson Chuang, Daniel Weiskopf , Torsten Moller. Hue-Preserving Color Blending. Tatiana Karaman. Overview: Hue. Degree to which a stimulus can be described as similar to, or different from, RGBY. http://www.larry-bolch.com/shade/color-light/Luminance2.jpg. Overview: Color Mapping.

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Hue-Preserving Color Blending

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  1. Johnson Chuang, Daniel Weiskopf, TorstenMoller Hue-Preserving Color Blending Tatiana Karaman

  2. Overview: Hue • Degree to which a stimulus can be described as similar to, or different from, RGBY. http://www.larry-bolch.com/shade/color-light/Luminance2.jpg

  3. Overview: Color Mapping • Quantitative and qualitative data representation • Visual Grouping http://www.cs.ubc.ca/~tmm/courses/533-07/readings/pravda/figure1.jpg

  4. Overview: 3D Color Mapping • Medical images  material components  color labels http://ieeexplore.ieee.org/ieee_pilot/articles/06/ttg2009061465/figures.html

  5. Overview: Transparency • Deal with occlusion problems in 3D structures http://www.cad.zju.edu.cn/home/chenwei/research/snapshots/Vis09_TAP.JPG

  6. Overview: Transparency through Alpha Compositing • Porter and Duff (1984) – compositing algebra • Basis for transparent surface and volume rendering is alpha blending • ‘over’ operator  this will be modified http://upload.wikimedia.org/wikipedia/commons/2/2a/Alpha_compositing.svg

  7. Overview: Physical and Perceptual Transparency • Physical: • Typically starting point for transparency in computer graphics http://www.e-onsoftware.com/products/vue/vue_10_infinite/images/PhysicalTranspL.jpg

  8. Overview: Physical and Perceptual Transparency • Perceptual: • Physical transparency is not required • Can be affected by many factors

  9. Overview: Physical and Perceptual Transparency • Perceptual: • Physical transparency is not required • Can be affected by many factors: • Luminance • Chromaticity • Subjective contours • Figural organization http://www.psy.ritsumei.ac.jp/~akitaoka/chiko2004.html

  10. Overview: Physical and Perceptual Transparency • Perceptual: • Physical transparency is not required • Can be affected by many factors: • Luminance • Chromaticity • Subjective contours • Figural organization http://en.wikipedia.org/wiki/File:Transparency2.gif

  11. Overview: Color and Transparency • Lacking research that looks at their interactions • Wang et al. (2008) proposed: • Avoid hue shift by using opposite colors for two semi-transparent layers • For >2 layers • Opposite hues for most important layers • Neutral hues for others

  12. Overview: Color and Transparency http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4658198 (Wang et al.)

  13. Overview: Color and Transparency • Locally modifying saturation http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4658198 (Wang et al.)

  14. Overview: Color and Transparency • Method: locally modify saturation http://silverthunder.com/images/Smoky_Blue_Horizon.jpg

  15. HueShift = Bad • Why? Shifting hues due to layered transparent data Possibility of false colors Mislabeling of data

  16. Proposed Model • Parameter-free model for composition of nominal data sets that include a combination of color and transparency • Independent control of chromatic and achromatic composition • Follows alpha blending approach • Luminance model from previous literature

  17. Design: Method for Hue Preserving Blending • Avoid false colors • Improve visual labeling by color • Even in transparent rendering

  18. Proposed Model in Action • Example: Tomato scan • Transfer function: variable opacity, three discreet colors

  19. Design Criteria • New compositing model has same luminance channel behavior as established compositing models.

  20. Design Criteria • New compositing model has same luminance channel behavior as established compositing models. • Achromatic channels should not be interfered with. http://thaines.com/content/research/sfs_pres.pdf

  21. Design Criteria • New compositing model has same luminance channel behavior as established compositing models. • Achromatic channels should not be interfered with. • Constant hue should be used for each nominal data entry for visual grouping

  22. Design Criteria • New compositing model has same luminance channel behavior as established compositing models. • Achromatic channels should not be interfered with. • Constant hue should be used for each nominal data entry for visual grouping • Artificial perceptual contours should be avoided

  23. New Operator Design • Modification of Porter and Duff’s additive alpha blending • Previous: C = CA + CB • Modified: Cnew =CA ⊕ CB

  24. New Operator Design • Original Porter and Duff form for C: • Weighted sum of input colors CA and CB C = (αAFA)CA + (αBFB)CB • Any color space related to RGB can be used

  25. New Operator Design • Modified approach – weights remain unchanged Cnew = (αAFA)CA ⊕ (αBFB)CB

  26. New Operator Design • Requirements for ⊕ • Luminance of CA⊕CB and CA + CB should be identical

  27. New Operator Design • Requirements for ⊕ • Luminance of CA⊕CB and CA + CB should be identical • Hue of Cnew should equal the most dominant hue

  28. New Operator Design • Requirements for ⊕ • Luminance of CA⊕CB and CA + CB should be identical • Hue of Cnew should equal the most dominant hue • Variation of saturation will be used to avoid color discontinuities

  29. Blending Process

  30. Blending Process

  31. Algorithm

  32. Results

  33. Results

  34. Results

  35. Results

  36. Results

  37. Results

  38. Benefits  • Can be included in any visualization tool that utilizes Porter and Duff compositing • Can be used for volume visualizations • Desaturated colors tend to be more energy efficient • Works for any RGB-related color space http://www.cs.sfu.ca/gruvi/Projects/HuePreservingColorBlending/

  39. Drawbacks  • Gray colors can be confusing and unnatural • Especially in large proportions • Order-dependent when >2 colors

  40. Are Our Goals Achieved? • Avoid false colors • Improve visual labeling by color • Even in transparent rendering

  41. Future Work • Research into role of chromatic channels in perceptual transparency • Optimizing transparency perception based on perceptual psychology • Implementing hue-preserving color blending for non-RGB color systems

  42. References • Chuang J, Weiskopf D, Moller T. Hue-preserving color blending. IEEE Trans Vis Comput Graph. 2009;15(6):1275-82 • Wang L, Giesen J, McDonnell T, Zolliker P, Mueller K. Color design for illustrative visualization. IEE Trans Vis Comput Graph. 2008;14(6):1739-1754

  43. Questions?

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