added a reversing section to colormap reference #23904

story645 · 2022-09-15T23:15:04Z

PR Summary

changed the note about reversing a colormap into a section of the colormap reference 'cause it was kind of buried in the preamble

PR Checklist

Tests and Styling

[N/A] Has pytest style unit tests (and pytest passes).
Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

[N/A] New features are documented, with examples if plot related.
[N/A] New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
[N/A] API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
Documentation is sphinx and numpydoc compliant (the docs should build without error).

jklymak · 2022-09-16T00:15:44Z

examples/color/colormap_reference.py

-A reversed version of each of these colormaps is available by appending
-``_r`` to the name, e.g., ``viridis_r``.


I'd keep this, and reference below with an anchor link.... Otherwise this looks great

timhoffm · 2022-09-16T05:49:02Z

examples/color/colormap_reference.py

+# A reversed version of any colormap is available by appending ``_r`` to the
+# name, for example:
+
+plot_color_gradients("Reversed ",


How about showing viridis and viridis_r in direct comparison instead of some random maps where I have to look up the unreversed version above to see the effect?

was going back and forth on that (they're just the first map of each section) as this is the tweet that inspired this PR

I think it felt too small, but also yes if it ain't broke...

Co-authored-by: Jody Klymak <jklymak@gmail.com> Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

tacaswell · 2022-09-16T19:09:28Z

examples/color/colormap_reference.py

+# Reversing a colormap
+# --------------------
+#
+# A colormap can be reversed by appending ``_r`` to the name. For example:


Suggested change

# A colormap can be reversed by appending ``_r`` to the name. For example:

# The built in colormaps have a reversed version named with a ``_r``

# appended to the name. For example:

Adding the _r does not reverse the color map, we generate the reverse color maps by calling cm.reversed() in

matplotlib/lib/matplotlib/cm.py

Lines 40 to 57 in 5c45952

def _gen_cmap_registry():

"""

Generate a dict mapping standard colormap names to standard colormaps, as

well as the reversed colormaps.

"""

cmap_d = {**cmaps_listed}

for name, spec in datad.items():

cmap_d[name] = ( # Precache the cmaps at a fixed lutsize..

colors.LinearSegmentedColormap(name, spec, _LUTSIZE)

if 'red' in spec else

colors.ListedColormap(spec['listed'], name)

if 'listed' in spec else

colors.LinearSegmentedColormap.from_list(name, spec, _LUTSIZE))

# Generate reversed cmaps.

for cmap in list(cmap_d.values()):

rmap = cmap.reversed()

cmap_d[rmap.name] = rmap

return cmap_d

It may be worth documenting the reversed method as well.

story645 added Documentation topic: color/color & colormaps labels Sep 15, 2022

jklymak reviewed Sep 16, 2022

View changes

timhoffm reviewed Sep 16, 2022

View changes

added a reversing section

54d24df

Co-authored-by: Jody Klymak <jklymak@gmail.com> Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

story645 force-pushed the color branch from 83771a5 to 54d24df Compare Sep 16, 2022

tacaswell reviewed Sep 16, 2022

View changes

added a reversing section to colormap reference #23904

added a reversing section to colormap reference #23904

story645 commented Sep 15, 2022 •

edited

jklymak Sep 16, 2022

timhoffm Sep 16, 2022

story645 Sep 16, 2022 •

edited

tacaswell Sep 16, 2022

		A reversed version of each of these colormaps is available by appending
		``_r`` to the name, e.g., ``viridis_r``.

	# A colormap can be reversed by appending ``_r`` to the name. For example:
	# The built in colormaps have a reversed version named with a ``_r``
	# appended to the name. For example:

	def _gen_cmap_registry():
	"""
	Generate a dict mapping standard colormap names to standard colormaps, as
	well as the reversed colormaps.
	"""
	cmap_d = {**cmaps_listed}
	for name, spec in datad.items():
	cmap_d[name] = ( # Precache the cmaps at a fixed lutsize..
	colors.LinearSegmentedColormap(name, spec, _LUTSIZE)
	if 'red' in spec else
	colors.ListedColormap(spec['listed'], name)
	if 'listed' in spec else
	colors.LinearSegmentedColormap.from_list(name, spec, _LUTSIZE))
	# Generate reversed cmaps.
	for cmap in list(cmap_d.values()):
	rmap = cmap.reversed()
	cmap_d[rmap.name] = rmap
	return cmap_d

added a reversing section to colormap reference #23904

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added a reversing section to colormap reference #23904

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story645 commented Sep 15, 2022 • edited

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jklymak Sep 16, 2022

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story645 Sep 16, 2022 • edited

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story645 commented Sep 15, 2022 •

edited

story645 Sep 16, 2022 •

edited