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Color Principles for Computer Graphics

Donald House 9/17/09 Artist ’ s slides by Lynette House. Color Principles for Computer Graphics. Physics of Color. Physiology of Color. Physiology of Color. 3 cone response curves Luminance efficiency. Artist ’ s Color. Hue Saturation Value. Value. Luminance

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Color Principles for Computer Graphics

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  1. Donald House 9/17/09 Artist’s slides by Lynette House Color Principles for Computer Graphics

  2. Physics of Color

  3. Physiology of Color

  4. Physiology of Color 3 cone response curves Luminance efficiency

  5. Artist’s Color Hue Saturation Value

  6. Value • Luminance • Dark to Light • Value range • High key • Middle key • Low key

  7. Hue - Paint Mixing • Physical mix of opaque paints • Primary: RYB • Secondary: OGV • Neutral: R + Y + B

  8. Hue - Light Mixing • Additive mix of colored lights • Primary: RGB • Secondary: CMY • Neutral = R + G + B

  9. Hue - Ink Mixing • Subtractive mix of transparent inks • Primary: CMY • Secondary: RGB • ~Black: C + M + Y • Actually use CMYKto get true black

  10. Hue - Ink Mixing Assumption: ink printed on pure white paper CMY = White – RGB: C = 1 – R, M = 1 – G, Y = 1 – B CMYK from CMY (K is black ink): K = min(C, M, Y) C = (C – K) / (1 – K), M = (M – K) / (1 – K), Y = (Y – K) / (1 – K)

  11. Saturation • Purity of color

  12. Perception of Color In the end, color is a perceptual phenomenon

  13. Color Constancy Perceived color is highly context dependent Allowing color recognition with variable lighting conditions

  14. Color Constancy Perceived color is highly context dependent Allowing color recognition with variable lighting conditions

  15. Simultaneous Contrast

  16. Simultaneous Contrast

  17. RGB Color Wheel • Warm/Cool • Complements • Split Complement • Analogous

  18. HSV Color Model HSV is a projection of the RGB space RGB cube HSV top view HSV cone

  19. HSV Color Model Hue, an angular measure (0 … 360)

  20. HSV Color Model Saturation, a fractional measure (0.0 … 1.0)

  21. HSV Color Model Value, a fractional measure (0.0 … 1.0)

  22. CIE 1931 Study Color Matching Experiment

  23. CIE Color Matching Functions CIE RGB Matching Functions CIE XYZ Matching Functions

  24. RGB from Spectrum RGB = x d

  25. XYZ from Spectrum XYZ = x d

  26. CIE xyY from CIE XYZ • CIE xyY color model is used to catalog colors: • x = X / (X + Y + Z) • y = Y / (X + Y + Z) • Y = luminance

  27. CIE xyY Color Cone

  28. CIE xyY Typical Display Gamut

  29. CIE Lu*v* and Lab Perceptually Uniform Spaces Lu*v* rescales xyYLab color opponents

  30. Color Picker

  31. End

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