Colormaps 101
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Colormaps 101 Sources – Russell Taylor Comp 290 course notes Colin Ware – Perception for Design IBM Web Site. Rachael Brady Visualization Friday Forum November 22, 2002. An Excellent Paper:

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An excellent paper

Colormaps 101Sources – Russell Taylor Comp 290 course notesColin Ware – Perception for DesignIBM Web Site

Rachael Brady

Visualization Friday Forum

November 22, 2002

An Excellent Paper:

A Rule-based Tool for Assisting Colormap Selection, L. Bergman, B. Rogowitz and L. Treinish. Proceedings of the IEEE Computer Society Visualization '95 pp. 118-125, October 1995.


An excellent paper

Color is useful for classification

Color is not needed to understand shape, spatial relationships of objects, movement

Laboratory assistant went 21 years without realizing he was color-blind


Color space rgb

Color Space: RGB

Taken from Russell Taylor II, UNC CS 290 Course Notes


Colorspace hsv

Colorspace: HSV

Taken from Russell Taylor II, UNC CS 290 Course Notes


Opponent process theory hering 1920

Opponent Process Theory (Hering 1920)

The six elementary colors are paired on 3 orthogonal axis:

Black-White, Red-Green, Yellow-Blue

Modified from Russell Taylor II, UNC CS 290 Course Notes


Color category perception

Color Category Perception

  • Task: Name the colors

  • Regions same > 75%

  • Nonuniform sizes

  • Why “rainbow scale” is so nonuniform

  • The fact that only 8 hues were named out of 210 different colors indicates that there may be only a few colors available for labeling.

Taken from Russell Taylor II, UNC CS 290 Course Notes


Other color issues

Other Color Issues

  • Color Blindness

    • Most red/green color blind (10% of males, 1% females)

  • Field Size

    • Avoid small spots, especially in yellow/blue

    • Small areas: strong, highly-saturated colors

    • Large areas: low saturation with slight differences

  • Conventions

    • U.S.: Red = danger, Green = life

    • China: Red = life, Green = death

    • Some scientific domains have color conventions

Taken from Russell Taylor II, UNC CS 290 Course Notes


Designing of a colormap

Designing of a colormap

  • Perceptually Ordered Sequence is required, such as black-white, red-green, blue-yellow, or saturation (dull->vivid)

  • Note: a perceptually ordered sequence will result from a series of colors that monotonically increase or decrease with respect to one or more of the color opponent channels

  • Use a Luminance Ordered Sequence for High Spatial Frequency Data

  • Use a Saturation Ordered Sequence for Low Spatial Frequency Data

  • Use several discrete colors when it is necessary to read back values (to avoid contrast effects)


Example colormaps

Example Colormaps

Source: Ware, Perception for Design


Not ordered red at both ends

Not ordered (red at both ends)

Taken from Russell Taylor II, UNC CS 290 Course Notes


Luminance gray scale

Luminance (Gray) Scale

Taken from Russell Taylor II, UNC CS 290 Course Notes


Saturation scale

Saturation Scale

Taken from Russell Taylor II, UNC CS 290 Course Notes


Hue scale

Hue Scale

Taken from Russell Taylor II, UNC CS 290 Course Notes


Hue luminence

Hue+Luminence

Taken from Russell Taylor II, UNC CS 290 Course Notes


Hue saturation

Hue+Saturation

Taken from Russell Taylor II, UNC CS 290 Course Notes


Black body radiation

Black Body Radiation

Taken from Russell Taylor II, UNC CS 290 Course Notes


Colormap choice should be linked to task atmospheric motion

Colormap Choice Should be Linked to TaskAtmospheric Motion

Bergman, Rogowitz, Treinish, IEEE Vis ‘95


Colormap choice should be linked to task pollution levels

Colormap Choice Should be Linked to TaskPollution Levels

Bergman, Rogowitz, Treinish, IEEE Vis ‘95


Color interaction

Color Interaction

Bergman, Rogowitz, Treinish, IEEE Vis ‘95


Color interaction1

Color Interaction

Bergman, Rogowitz, Treinish, IEEE Vis ‘95


Trumbo s principles

Trumbo’s Principles

  • Univariate

    • Order: ordered values should be represented by perceptually-ordered colors

    • Separation: significantly different levels should be represented by distinguishable colors

Modified from Russell Taylor II, UNC CS 290 Course Notes


Ordered and double ended

Ordered (and double-ended)

  • Tufte ‘97, pg. 76.

Taken from Russell Taylor II, UNC CS 290 Course Notes


Not ordered

Not ordered

  • Tufte ‘97, pg. 77.

Taken from Russell Taylor II, UNC CS 290 Course Notes


Double ended scale

Double-ended Scale

  • Two distinct scales joined at neutral middle

  • Characteristics

    • segments values into two groups

    • can emphasize both extremes of data range

Taken from Russell Taylor II, UNC CS 290 Course Notes


Double ended income

Double-Ended Income

  • Olson ‘97, fig. 11-8.

Taken from Russell Taylor II, UNC CS 290 Course Notes


In summary

In Summary

  • Interesting values?

    • Position striking colors at interesting values

  • Zero in range?

    • Double-ended scale

  • High spatial frequency?

    • Vary lightness in addition to hue

Taken from Russell Taylor II, UNC CS 290 Course Notes


An excellent paper

Color Theory in Cartography is well developed.

Cynthia Brewer at Penn State has a great color creator for discrete, monotonic color sequences.

http://www.personal.psu.edu/faculty/c/a/cab38/ColorBrewerBeta.html


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