Color CS5540 HCI Rich Riesenfeld Fall 2011 Lecture Set 25 Fall 20111

2 Color Issues Physical nature of colorPhysical nature of color Eye mechanism of colorEye mechanism of color –Rods, Cones, tri-stimulus model Brain mechanism of colorBrain mechanism of color Color spacesColor spaces Aesthetic and physiologicalAesthetic and physiological

3 Color Color is complicated!Color is complicated! –Highly nonlinear –No singular model to explain all Many simplistic models, explanationsMany simplistic models, explanations Many mythsMany myths Much new knowledgeMuch new knowledge

4 Color Many phenomena to explainMany phenomena to explain –High light / low light –Illusions –Color blindness –Metamers

5 Additive Primary Colors (1,0,1) magenta (0,0,1) blue (0,1,0) (0,1,1) cyan green (1,0,0) red (1,1,0) yellow

6 Additive Primary Colors (0,1,0) green (1,0,0) red (1,1,0) yellow

Fall Additive Primary Colors (1,0,1) magenta (0,0,1) blue (1,0,0) red

Fall Subtractive Primary Colors (1,0,1) magenta (0,0,1) blue (1,1,0) yellow (0,1,0) green (1,0,0)red (0,1,1) cyan

Fall Additive Primary Colors (0,0,1) blue (0,1,0) (0,1,1) cyan green

Fall Subtractive Primary Colors (1,0,1) magenta (1,1,0) yellow (1,0,0)red

Fall Subtractive Primary Colors (0,1,0) (0,1,1) cyan green (1,1,0) yellow

Fall Subtractive Primary Colors (1,0,1) magenta (0,0,1) blue (0,1,1) cyan

13 Wavelength Spectrum infrared light ultraviolet light Wavelength (nm) Seen in physics, physical phenomena (rainbows, prisms, etc)Seen in physics, physical phenomena (rainbows, prisms, etc) 1 Dimensional color space1 Dimensional color space

Fall Wavelength Spectrum

15 Color Space “Navigating,” moving around in a color space, is tricky“Navigating,” moving around in a color space, is tricky Many representations (spaces) for all colorsMany representations (spaces) for all colors Can you get to a nearby color? Can you predictably adjust a color?Can you get to a nearby color? Can you predictably adjust a color?

Fall Color Cube (0,0,0) (0,1,0) (0,1,1) (1,0,1) (0,0,1) (1,0,0) (1,1,0) blue cyan white (1,1,1) black green yellow magenta red gray

Fall Color Cube (0,1,0) (0,1,1) (1,0,1) (0,0,1) (1,0,0) (1,1,0) blue cyan white (1,1,1) green yellow magenta red

Fall Complementary Colors Add to Gray (0,1,1) (1,0,1) (0,0,1) (1,0,0) (1,1,0) blue cyan white (1,1,1) yellow magenta red (0,1,0) green

Fall Complementary Colors Looking at color cube along major diagonal

20 (H, S,V) Color Space Hue: ColorHue: Color –Chroma Saturation: Strength of a colorSaturation: Strength of a color –Neutral gray has 0 saturation Brightness/Value: Intensity of light emanating from imageBrightness/Value: Intensity of light emanating from image

Fall The hue of an object may be blue, but the terms light and dark distinguish the brightness of one object from another. (Hue, Saturation, Value/Intensity) (H, S,V) Color Space

22 Saturation

Fall Other HSX Color Spaces (Cones) 0.0 cyan white1.0 yellow magenta red 120 ˚ green black 0˚0˚ V 240 ˚ blue S H

Another HSX Color Space (double cone) 0.0 cyan white 1.0 magenta red black 0˚0˚ S L H 240 ˚ blue green 120 ˚ yellow 24 Fall

25 Tristimulus Color Theory Any color can be “matched” by a mixture of three fixed base colors (primaries)Any color can be “matched” by a mixture of three fixed base colors (primaries) Eye has three kinds of color receptors called conesEye has three kinds of color receptors called cones Eye also has rods (low light receptors)Eye also has rods (low light receptors)

Fall Color Receptors in Eye Red, Green, Blue Long, Medium, Short

Fall Color Receptors in Eye

Fall Wavelength Spectrum infrared light ultraviolet light Wavelength (nm)

29 Why are runway lights blue?Why are runway lights blue? Why are console lights green?Why are console lights green? Why color is the Kodak box?Why color is the Kodak box? Color Response - 1

30 What color is the Kodak box? Color Response - 2 (nm)

31 Color Matching Experiments Given a reference color, try to match it identicallyGiven a reference color, try to match it identically What does “negative red,” or “negative color” mean??What does “negative red,” or “negative color” mean??

32 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 )

33 CIE Color Space x = X / ( X + Y + Z ) y = Y / ( X + Y + Z ) z = Z / ( X + Y + Z ) x + y + z = 1

Fall Color Gamuts: CIE Color Chart

Fall Color Gamuts: CIE Color Chart

Fall Color Gamuts: CIE Color Chart

37 Color Applets edu/brown/cs/exploratories/applets/combinedColorMixing /combined_color_mixing_java_browser.html edu/brown/cs/exploratories/applets/combinedColorMixing /combined_color_mixing_java_browser.html /repository/edu/brown/cs/exploratories/applets/comb inedColorMixing/combined_color_mixing_java_plu gin.html /repository/edu/brown/cs/exploratories/applets/comb inedColorMixing/combined_color_mixing_java_plu gin.html

Fall Another Space

39 Important Concepts AdaptationAdaptation –Slow process ConstancyConstancy –Immediate process

Fall Output to the Brain from Eye R G B B B - RGR-GRGR-G B R G YY YY

Fall Mechanism

42 Lecture Set 25 Fall

Fall Color Receptors in Eye Red, Green, BlueRed, Green, Blue Long, Medium, Short

44 Saturation