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Color

Color. Prof. Muhammad Saeed. Color Models:. Wavelength. Spectrum. Note that the rainbow does not contain any magenta. It is nonspectral . Color Models:. Newton’s Color Wheel. Replaced Aristotle’s color model based on light and darkness. Color Models:. Spectrum. W a v e l e n g t h.

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Color

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  1. Color Prof. Muhammad Saeed

  2. Color Models: Wavelength Spectrum Note that the rainbow does not contain any magenta. It is nonspectral. Dept. Comp. Sc. & IT

  3. Color Models: Newton’s Color Wheel Replaced Aristotle’s color model based on light and darkness. Dept. Comp. Sc. & IT

  4. Color Models: Spectrum W a v e l e n g t h • Seen in physics, physical phenomena (rainbows, prisms, etc) • 1 Dimensional color space ultraviolet light Infrared light 700 600 500 400 Wavelength (nm) Dept. Comp. Sc. & IT

  5. Color Color Sensitivity and Models Dept. Comp. Sc. & IT

  6. 400 440 480 520 560 600 640 680 Color Models: Tristimulus Color Theory Color Receptors in Eye • Any color can be matched by a mixture of three fixed base colors (primaries) • Eye has three kinds of color receptors called cones • Eye also has rods (low light receptors) Fraction of light absorbed by each type of cone Wavelength λ (nm) Dept. Comp. Sc. & IT

  7. Color Models: Wavelength is in nanometers Dept. Comp. Sc. & IT

  8. Traditional, Artistic: RGB CMY CMYK HSV HSL Color Models: Color Spaces (Models) • Perceptually Based: • XYZ (Tristimulus) • Xyz • Hunter-Lab • CIE-L*ab • CIE-L*CH° • CIE-L*CH° • CIE-L*ab • CIE-L*uv Dept. Comp. Sc. & IT

  9. Color Models: Tints, Tones and Shades: Tints Pure Color White Tones Grays Shades Black Dept. Comp. Sc. & IT

  10. (1,1,0) yellow green (0,1,0) cyan (0,1,1) Color Models: Additive Primaries: (r,g,b) red (1,0,0) white (1,1,1) magenta (1,0,1) blue (0,0,1 ) Dept. Comp. Sc. & IT

  11. gray Color Models: RGB Model: cyan blue (0,1,1) (0,0,1 ) magenta white (1,0,1) (1,1,1) green black (0,0,0) (0,1,0) red (1,1,0) (1,0,0) yellow Dept. Comp. Sc. & IT

  12. Color Models: Color Cube cyan (0,0,1 ) blue (0,1,1) magenta white (1,0,1) (1,1,1) green (0,1,0) red yellow (1,0,0) (1,1,0) Dept. Comp. Sc. & IT

  13. Color Models: Looking at color cube along major diagonal Dept. Comp. Sc. & IT

  14. Color Models: Subtractive Primaries: (r,g,b) red (1,0,0) yellow magenta (1,1,0) (1,0,1) black (0,0,0) green blue (0,1,0) (0,0,1) cyan (0,1,1) Dept. Comp. Sc. & IT

  15. Color Models: H S V MODEL • Introduced by Albet Munsell, late 1800s. • He was an artist andscientist • Hue: Color • Saturation/Chroma: Strength of a color • Neutral gray has 0 saturation • Brightness/Value: • Intensity of light emanating from image V 120˚ yellow green 1.0 0˚ cyan red blue magenta 240˚ H S 0.0 Dept. Comp. Sc. & IT

  16. Color Models: Saturation Dept. Comp. Sc. & IT

  17. Color Models: James C. Maxwell’s Color Model green unsaturated cyan cyan yellow  white blue red magenta Dept. Comp. Sc. & IT

  18. Color Models: L white 1.0 HLS Model (Hue, Lightness, Saturation) red 0˚ H S black 0.0 Dept. Comp. Sc. & IT

  19. Color Models: HSV toRGB Dept. Comp. Sc. & IT

  20. Color Models: RGB to HSV Dept. Comp. Sc. & IT

  21. Color Models: CIE* Color Space ( X, Y, Z) represents an imaginary basis that does not correspond to what we see Define the normalized coordinates: x = X / ( X + Y +Z)y = Y / ( X + Y+ Z )z = Z / ( X+ Y + Z ) * Commission Internationale de l'Êclairage Dept. Comp. Sc. & IT

  22. Color Models: CIE Color Space of Visible Colors y x = X / ( X + Y +Z)y = Y / ( X + Y+ Z )z = Z / ( X+ Y + Z ) x x + y + z = 1 z The projection of the plane of the triangle onto the (X,Y) plane forms the chromaticity diagram that follows. Dept. Comp. Sc. & IT

  23. Color Models: Color Gamuts:CIEColor Chart green yellow cyan white red blue magenta Dept. Comp. Sc. & IT

  24. Color Models: 520 nm Color Gamuts:CIEColor Chart ideal green 540 nm 510 nm 560 nm green 500 nm 580 nm yellow 600 nm cyan white red 490 nm 700 nm blue ideal blue ideal red 400 nm Dept. Comp. Sc. & IT

  25. Color Models: Color Gamuts:CIEColor Chart Dept. Comp. Sc. & IT

  26. Color Models: Color Gamuts:CIEColor Chart The Color Gamuts of different displays and printers are not likely to match. Printers usually have smaller gamuts. B R G Dept. Comp. Sc. & IT

  27. Color Models: CIE Chromaticity Diagram: Dept. Comp. Sc. & IT

  28. Color Models: Color Gamuts:CIEColor Chart The additive colors C1and C2 combine to form C3on the line connecting C1 and C2. C2 C3 C1 Dept. Comp. Sc. & IT

  29. Color Models: Reproducible colors: Color monitors are based on adding three the output of three different light emitting phosphors. The nominal position of these on the CIE diagram is given by: x y z Red0.628 0.346 0.026 Green0.268 0.588 0.144 Blue 0.150 0.07 0.780 Dept. Comp. Sc. & IT

  30. RGB to CIE: The monitor RG B representation is related to the CIE colors by the equation: Color Models: Color (RGB) to Gray Transformation: Red *= 0.33, Green *= 0.56, Blue *= 0.11 Dept. Comp. Sc. & IT

  31. Color Models: CIE Model (Commission Internationale de I’ Eclairage): CIE Chromaticity Diagram Dept. Comp. Sc. & IT

  32. Color Models: Gamma Correction: Dept. Comp. Sc. & IT

  33. End Color Dept. Comp. Sc. & IT

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