Date post: | 13-Jan-2016 |
Category: |
Documents |
Upload: | ernest-brent-fletcher |
View: | 212 times |
Download: | 0 times |
Colormaps 101
Sources – Russell Taylor Comp 290 course notesColin Ware – Perception for Design
IBM Web Site
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.
Rachael Brady
Visualization Friday Forum
November 22, 2002
Color is useful for classification
Color is not needed to understand shape, spatial relationships of objects, movementLaboratory assistant went 21 years without realizing he was color-blind
Color Space: RGB
Taken from Russell Taylor II, UNC CS 290 Course Notes
Colorspace: HSV
Taken from Russell Taylor II, UNC CS 290 Course Notes
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
• 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• 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•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
Source: Ware, Perception for Design
Not ordered (red at both ends)
Taken from Russell Taylor II, UNC CS 290 Course Notes
Luminance (Gray) Scale
Taken from Russell Taylor II, UNC CS 290 Course Notes
Saturation Scale
Taken from Russell Taylor II, UNC CS 290 Course Notes
Hue Scale
Taken from Russell Taylor II, UNC CS 290 Course Notes
Hue+Luminence
Taken from Russell Taylor II, UNC CS 290 Course Notes
Hue+Saturation
Taken from Russell Taylor II, UNC CS 290 Course Notes
Black Body Radiation
Taken from Russell Taylor II, UNC CS 290 Course Notes
Colormap Choice Should be Linked to TaskAtmospheric Motion
Bergman, Rogowitz, Treinish, IEEE Vis ‘95
Colormap Choice Should be Linked to TaskPollution Levels
Bergman, Rogowitz, Treinish, IEEE Vis ‘95
Color Interaction
Bergman, Rogowitz, Treinish, IEEE Vis ‘95
Color Interaction
Bergman, Rogowitz, Treinish, IEEE Vis ‘95
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)
• Tufte ‘97, pg. 76.Taken from Russell Taylor II, UNC CS 290 Course Notes
Not ordered
• Tufte ‘97, pg. 77.Taken from Russell Taylor II, UNC CS 290 Course Notes
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
• Olson ‘97, fig. 11-8.
Taken from Russell Taylor II, UNC CS 290 Course Notes
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
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