[yt-dev] Default colormap

[Matthew Turk]

Hi Stuart and everyone else,

This is great info.  I appreciate everyone's thoughtful replies.

Having both a sequential colormap (which would replace algae) and a
diverging colormap, would be awesome.  The Paraview devs shipped the
new matplotlib ones (like Inferno) in 5.0.  I think it would be a fun
experiment to see if we can come up with something sufficiently
"branded" or different.  And then if we can't, fall back on something
like Inferno?

-Matt

On Wed, Jan 6, 2016 at 12:48 PM, Levy, Stuart A <salevy at illinois.edu> wrote:
> There was a fair bit of discussion about colormaps - terrible, useful,
> beautiful - at IEEE Vis last October.   The viridis colormap was a featured
> one.   So was the traditional rainbow, which lots of info-vis and perceptual
> people piled on to criticize.
>
> Among design criteria for a continuous-valued colormap is whether it's
> "sequential" (like the typical yt colormap, or viridis) or "diverging".
> You'd want a diverging colormap to show signed deviations from a norm -
> where the eye should be caught by places where a value is either much less
> than, or much more than, something in the middle.   Is it worth offering a
> typical divergent colormap, as well as a new typical sequential one, in yt?
>
> Note that among the Stefan van der Walt & Nathaniel Smith writeup (
> http://bids.github.io/colormap/ ) on their development of better cmaps, they
> use Nathan Goldbaum's galaxy evolution as a test case for six (sequential)
> examples! => http://vorpus.org/~njs/goldbaum-galaxies-all-colormaps.mkv
>
> A neat web site with sample colormaps - aimed at mapping discrete values on
> geographic maps, so not directly applicable but cool - is this, by Cynthia
> Brewer and Mark Harrower at PSU:
>     http://colorbrewer2.org/
> It has a library of predesigned cmaps, and lets you sift them by being
> colorblind-safe, photocopy safe, etc.
> ________________________________
> From: yt-dev [yt-dev-bounces at lists.spacepope.org] on behalf of B.W. Keller
> [kellerbw at mcmaster.ca]
> Sent: Wednesday, January 06, 2016 12:13
> To: yt-dev at lists.spacepope.org
> Subject: Re: [yt-dev] Default colormap
>
> There is a really excellent paper on designing color maps called "Color
> Sequences for Univariate Maps: Theory, Experiments, and Principles" that you
> can get here:
> http://ccom.unh.edu/sites/default/files/publications/Ware_1988_CGA_Color_sequences_univariate_maps.pdf
>
> If we design a new colormap, this would be a good reference along with those
> scipy resources.  I personally would love to have an accessible, yt-custom
> colormap.
>
> On Wed, Jan 6, 2016 at 11:50 AM, Erik Schnetter <schnetter at gmail.com> wrote:
>>
>> I think there are several colourmaps that were created when Viridis
>> was invented. I personally like Inferno.
>>
>> -erik
>>
>> On Wed, Jan 6, 2016 at 11:34 AM, Nathan Goldbaum <nathan12343 at gmail.com>
>> wrote:
>> > I would also be for coming up with our own colormap. That said, I think
>> > simply modifying algae won't be enough, since it is too perceptually
>> > nonlinear.
>> >
>> > On Wed, Jan 6, 2016 at 10:32 AM, John ZuHone <jzuhone at gmail.com> wrote:
>> >>
>> >> I would go for modifying algae.
>> >>
>> >> > On Jan 6, 2016, at 11:30 AM, Matthew Turk <matthewturk at gmail.com>
>> >> > wrote:
>> >> >
>> >> > Hi folks,
>> >> >
>> >> > For a long time we've used "algae," which was designed by Britton
>> >> > about eight years ago, as the default colormap.  This has been really
>> >> > nice for "branding" yt -- if you see an algae plot, it's probably
>> >> > (not
>> >> > definitely) made with yt.  But it's also not accessible from a
>> >> > colorblindness perspective.  Stefan van der Walt has been giving some
>> >> > really great talks lately about building a better colormap for
>> >> > matplotlib (e.g., https://www.youtube.com/watch?v=xAoljeRJ3lU ) which
>> >> > culminated in viridis, which is shipping in recent versions of
>> >> > matplotlib and will become the default.
>> >> >
>> >> > In support of this, he built a tool called viscm which can generate
>> >> > reduced versions of colormaps to show what they would be like with
>> >> > varying degrees of insensitivity to color.  I've generated outputs
>> >> > from viscm of three of the custom colormaps we ship with yt:
>> >> >
>> >> > Algae: https://images.hub.yt/u/fido/m/d275d5e1-png/
>> >> > Cubehelix: https://images.hub.yt/u/fido/m/8e698928-png/ (I believe
>> >> > this is now also shipped with MPL)
>> >> > Kamae: https://images.hub.yt/u/fido/m/e0e40efa-png/
>> >> >
>> >> > I love algae, but it's not the best from an accessibility
>> >> > perspective.
>> >> >
>> >> > I'd like to propose that we use a new default colormap.  If we do
>> >> > this, I see two options:
>> >> >
>> >> > * Retain a "branding" by developing a new one either by using the
>> >> > techniques used by matplotlib (or one of the maps they opted not to
>> >> > use) or by modifying algae to be more accessible; looking at the
>> >> > response functions, I suspect it would be reasonably possible to
>> >> > modify it.  (Modifying algae is my preference.)
>> >> > * Use viridis (which we may then have to ship if we have older
>> >> > versions of matplotlib to support)
>> >> >
>> >> > -Matt
>> >> > _______________________________________________
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>>
>> --
>> Erik Schnetter <schnetter at gmail.com>
>> http://www.perimeterinstitute.ca/personal/eschnetter/
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