I590 Interactive Visual Analytics Week 4 Gestalt Laws Color Perception Khairi Reda | redak@iu.edu School of Informa5cs & Compu5ng, IUPUI
Homework 0 Avg: 9.16 Min: 7 Max: 10
Last week Visual percep7on, edge detec7on, visual illusions, and popouts Our visual system see differences, not absolute values, and is aIracted to edges. We can easily see objects that are different in color and shape, or that are in mo5on (popouts) Use color and shape sparingly to make the important informa5on pop out
This week More on visual percep7on: • Gestalt principles • Color percep5on • Color spaces
Gestalt grouping principles
Gestalt grouping principles gestalt : form in German “The whole is other than the sum of its parts” Our brain has innate capacity to see paIerns that transcend the visual s5muli the produce them
proximity Andy Rutledge, “Gestalt Principles of Perception”
proximity Alex Lex
proximity B. Wong, “Gestalt Principles, I”
similarity B. Wong, “Gestalt Principles, I”
similarity Andy Rutledge, “Gestalt Principles of Perception”
connectedness Ware, “Information Visualization”
link surface outline enclosure Alex Lex
A li=le experiment… How many groups do you see? color size shape proximity similarity similarity similarity Based on a slide by Alex Lex
A li=le experiment… How many groups do you see? color size shape proximity similarity similarity similarity Based on a slide by Alex Lex
A li=le experiment… How many groups do you see? color size shape proximity similarity similarity similarity Based on a slide by Alex Lex
grouping B. Wong, “Gestalt Principles, I”
grouping
grouping Jorge Camoes Via Miriah Meyer
grouping - common fate
closure
closure
figure / background Mariah Meyer
Gestalt principles similarity: objects that look like each other (in size, color, or shape) are related proximity: objects that are visually close to each other are related connections: objects that are visually connected are related closure: we see incomplete shapes as complete figure / ground: elements are perceived as either figures or background common fate: elements with the same moving direc5on are perceived as a unit Mariah Meyer
color The Huffington Post
color the property possessed by an object of producing different sensa5ons on the eye as a result of the way the object reflects or emits light -Oxford dictionary
light Electromagne5c radia5on within a certain range [400nm - 700nm] of the electromagne5c spectrum more energy
light Mariah Meyer
Trichromacy
Trichromacy Normal human color vision is 3 dimensional Derived from three cone types (short, medium, and large wave-length sensi5vity) Each type of cone contains a specific photosensi5ve pigment that reacts to a certain wavelength of light Based on a slide by Mariah Meyer
Trichromacy easy to read difficult to read easy to read difficult to read
Opponent-process theory Explains how signals are processed Visual perceptual system detects differences in the response of cones + + - - red-green yellow-blue luminance opponent channel opponent channel
Sensitivity to spatial detail The luminance channel has greater ability to resolve smaller detail C. Ware, Visual Thinking for Design
Sensitivity to spatial detail C. Ware, Visual Thinking for Design
“Important” colors These colors have a name in virtually every human language Their seman5cs and connota5ons are culture- specific
Conventions hue saturation luminance
Color deficiencies
Color deficiencies Some5mes caused by faculty cones, some5mes by faulty pathways red-green weakness is the most common type 8% of (North American) makes, 0.5% of female Can be explained by opponent color theory normal re5na Protanopic Based on a slide by Miriah Meyer
lacking red cones lacking green cones lacking blue cones Via Miriah Meyer
difficult to dis5nguish for people with Deuteranopia
Design critique • What is the visualiza5on http://tinyurl.com/gueqapz about? • What data is represented in the visualiza5on? And how? • What are the interac5ons used? • What ques5ons can we answer with the visualiza5on? • Do you like the visualiza5on? • Are there any improvements that can be made to the design?
Color spaces
light 1. pure yellow: 580 nm 2. color matching yellow
Tristimulus color matching red green test color blue
Tristimulus color matching red green test color 580nm blue
Tristimulus color matching red 0.17 green 0.17 test color 580nm blue 0
RGB color space Each point within the cube is defined by a 3D vector (r, g,b) Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color red, green, and blue primaries needed to reproduce the color 1.0 G 1.0 R B 1.0
RGB color space Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color yellow (1.0, 1.0, 0.0) 1.0 1.0 1.0
RGB color space Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color 1.0 (1.0, 0.6, 1.4) 1.0 1.0
RGB color space Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color 1.0 1.0 1.0 1.0 magenta (1.0, 0.0, 1.0) 1.0 1.0
RGB color space Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color 1.0 1.0 white (1.0, 1.0, 1.0) 1.0 1.0 1.0 1.0
RGB color space Each point within the cube is defined by a 3D vector (r, g,b) and represents a unique color The r, g, b coordinates of the vector reflect a combina5on of red, green, and blue primaries needed to reproduce the color 1.0 1.0 1.0 1.0 black (0.0, 0.0, 0.0) 1.0 1.0
RGB color space G R B
what colors combina7on can be used to re- producing the visible light spectrum by mixing? • red, yellow, blue • red, green, blue • orange, green, violet • cyan, magenta, yellow • all of the above Miriah Meyer
Light mixing (RGB) Addi5ve mixing of colored lights
Light mixing (RGB) LCD display closeup Wikipedia
Ink mixing (CMY / CMYK) Subtrac5ve mixing of inks printed on white paper
CMY composite CMYK composite Color picture Wikipedia
what colors combina7on can be used to re- producing the visible light spectrum by mixing? red, yellow, blue • red, green, blue • orange, green, violet • cyan, magenta, yellow • • all of the above , almost Miriah Meyer
Tristimulus color matching red green test color 500nm blue
Tristimulus color matching red green test color 500nm blue
Tristimulus color matching red green test color 500nm blue
Tristimulus color matching red green test color 500nm blue
Opps
CIE color space At a mee5ng in of the CIE in 1931 • Let’s have imaginary primary colors! • Construct linear, possibly non-realizable combina5ons of • primaries so that color matching func5ons are posi5ve throughout the visible light X, Y, Z primaries • Can be linearly transformed from RGB (and vice versa) • Based on a slide by Siddhartha Chaudhuri
CIE color space
1.0 Y Y 1.0 X X Z Z 1.0
Y X Z
CIE chromaticity diagram
CIE chromaticity diagram White
CIE chromaticity diagram G Y R
CIE chromaticity diagram White
CIE chromaticity diagram RGB color space
CIE chromaticity diagram
Perceptual color spaces A change in the amount of color value should produce a propor5onal change in the way we see the color Via Miriah Meyer
HSL Rearrangement of the RGB color space into a cylinder to be more intui5ve and perceptually relevant • hue: what people think of as color • saturation: the vividness of the color • luminance: amount of black mixed in
hue saturation luminance
Guidelines for using color in visualization
Colormap Specifies a mapping between [0, 8] color and values categorical sequential discrete vs. vs. vs. ordered diverging continuous Match colormap to data type & task
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