Perceptions of matplotlib colormaps

A look at which matplotlib colormaps are most perceptual, as well as which will print well to grayscale and be accessible to viewers with color deficiencies.

Transcript

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

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

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

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7. Perceived Lightness: Weber-Fechner Law (and Stevens)
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   Additional Parts Black
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   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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8. Improvement to Binary Colormap?
   Kristen M. Thyng (Texas A&M) SciPy 2014 July 10, 2014 6 / 15
   

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

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

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

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

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

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

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

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

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

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

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21. 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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22. 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
    

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