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Perceptions of matplotlib colormaps Kristen M. Thyng Texas A&M University July 10, 2014 Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 1 / 15

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CIELAB Color Model http://eschicleypega.blogspot.com Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 2 / 15

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Lightness of matplotlib Colormaps http://matplotlib.org/examples/color/colormaps reference.html Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 3 / 15

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Lightness of matplotlib Colormaps Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 3 / 15

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Lightness of matplotlib Colormaps http://matplotlib.org/examples/color/colormaps reference.html Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 4 / 15

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Lightness of matplotlib Colormaps Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 4 / 15

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Perceived Lightness: Weber-Fechner Law (and Stevens) 1 1 2 2 3 4 4 Additional Parts Black 8 Albers, J. (1975). Interaction of color. Yale University Press. Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 5 / 15

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Improvement to Binary Colormap? Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 6 / 15

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Improvement to Binary Colormap? Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 6 / 15

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Printing to Grayscale Lots of ways to convert to grayscale Gray = (Red * 0.2126 + Green * 0.7152 + Blue * 0.0722) (or similar∗) Use luminance ∗ http://www.tannerhelland.com/3643/grayscale-image-algorithm-vb6/ Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 7 / 15

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matplotlib Colormaps in Grey Scale Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 8 / 15

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matplotlib Colormaps in Grey Scale Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 8 / 15

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matplotlib Colormaps in Grey Scale Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 8 / 15

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matplotlib Colormaps in Grey Scale Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 8 / 15

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matplotlib Colormaps in Grey Scale Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 8 / 15

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Color Blindness Protanopia (2% male population, half mild form) Deuteranopia (6% male population, mostly mild form) http://www.color-blindness.com Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 9 / 15

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Color Blindness http://aspnetresources.com/tools/colorBlindness Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 10 / 15

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Color Blindness http://aspnetresources.com/tools/colorBlindness Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 11 / 15

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Color Blindness http://aspnetresources.com/tools/colorBlindness Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 12 / 15

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Color Blindness http://aspnetresources.com/tools/colorBlindness Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 13 / 15

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Recommendations Best colormap depends on application, but for form information, perceptual colormaps are best Perceptual colormaps monotonically increase with lightness Not clear (to me) what functional relationship with L is best Many ways to convert to grayscale — luminance is a good proxy to decide on a good map Most common color blindness problem is red-green — try to avoid for reaching audiences most effectively Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 14 / 15

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Resources All around helpful information on colormaps: Matteo Niccoli: http://mycarta.wordpress.com/2012/05/29/the- rainbow-is-dead-long-live-the-rainbow-series-outline/ Comparison of 7 methods of converting to grayscale: http://www.tannerhelland.com/3643/grayscale-image-algorithm-vb6/ Color blindness: http://www.color-blindness.com Link to slides: https://github.com/dmcdougall/scipy14-colormaps Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 15 / 15