Skip to content

added a reversing section to colormap reference #23904

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Sep 24, 2022
+69 −13
Merged

added a reversing section to colormap reference #23904

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 20 additions & 6 deletions examples/color/colormap_reference.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,16 +6,17 @@
Reference for colormaps included with Matplotlib.
A reversed version of each of these colormaps is available by appending
``_r`` to the name, e.g., ``viridis_r``.
``_r`` to the name, as shown in :ref:`reverse-cmap`.
See :doc:`/tutorials/colors/colormaps` for an in-depth discussion about
colormaps, including colorblind-friendliness.
colormaps, including colorblind-friendliness, and
:doc:`/tutorials/colors/colormap-manipulation` for a guide to creating
colormaps.
"""

import numpy as np
import matplotlib.pyplot as plt


cmaps = [('Perceptually Uniform Sequential', [
'viridis', 'plasma', 'inferno', 'magma', 'cividis']),
('Sequential', [
Expand All @@ -40,7 +41,6 @@
'gist_rainbow', 'rainbow', 'jet', 'turbo', 'nipy_spectral',
'gist_ncar'])]


gradient = np.linspace(0, 1, 256)
gradient = np.vstack((gradient, gradient))

Expand All @@ -52,7 +52,7 @@ def plot_color_gradients(cmap_category, cmap_list):
fig, axs = plt.subplots(nrows=nrows, figsize=(6.4, figh))
fig.subplots_adjust(top=1-.35/figh, bottom=.15/figh, left=0.2, right=0.99)

axs[0].set_title(cmap_category + ' colormaps', fontsize=14)
axs[0].set_title(f"{cmap_category} colormaps", fontsize=14)

for ax, cmap_name in zip(axs, cmap_list):
ax.imshow(gradient, aspect='auto', cmap=cmap_name)
Expand All @@ -67,7 +67,21 @@ def plot_color_gradients(cmap_category, cmap_list):
for cmap_category, cmap_list in cmaps:
plot_color_gradients(cmap_category, cmap_list)

plt.show()

###############################################################################
# .. _reverse-cmap:
#
# Reversed colormaps
# ------------------
#
# Append ``_r`` to the name of any built-in colormap to get the reversed
# version:

plot_color_gradients("Original and reversed ", ['viridis', 'viridis_r'])

# %%
# The built-in reversed colormaps are generated using `.Colormap.reversed`.
# For an example, see :ref:`reversing-colormap`

#############################################################################
#
Expand Down
14 changes: 7 additions & 7 deletions lib/matplotlib/colors.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -870,13 +870,13 @@ def reversed(self, name=None):
"""
Return a reversed instance of the Colormap.

.. note:: This function is not implemented for base class.
.. note:: This function is not implemented for the base class.

Parameters
----------
name : str, optional
The name for the reversed colormap. If it's None the
name will be the name of the parent colormap + "_r".
The name for the reversed colormap. If None, the
name is set to ``self.name + "_r"``.

See Also
--------
Expand Down Expand Up @@ -1079,8 +1079,8 @@ def reversed(self, name=None):
Parameters
----------
name : str, optional
The name for the reversed colormap. If it's None the
name will be the name of the parent colormap + "_r".
The name for the reversed colormap. If None, the
name is set to ``self.name + "_r"``.

Returns
-------
Expand Down Expand Up @@ -1179,8 +1179,8 @@ def reversed(self, name=None):
Parameters
----------
name : str, optional
The name for the reversed colormap. If it's None the
name will be the name of the parent colormap + "_r".
The name for the reversed colormap. If None, the
name is set to ``self.name + "_r"``.

Returns
-------
Expand Down
42 changes: 42 additions & 0 deletions tutorials/colors/colormap-manipulation.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -255,6 +255,48 @@ def plot_linearmap(cdict):

plot_examples([cmap1, cmap2])

#############################################################################
# .. _reversing-colormap:
#
# Reversing a colormap
# ====================
#
# `.Colormap.reversed` creates a new colormap that is a reversed version of
# the original colormap.

colors = ["#ffffcc", "#a1dab4", "#41b6c4", "#2c7fb8", "#253494"]
my_cmap = ListedColormap(colors, name="my_cmap")

my_cmap_r = my_cmap.reversed()

plot_examples([my_cmap, my_cmap_r])
# %%
# If no name is passed in, ``.reversed`` also names the copy by
# :ref:`appending '_r' <registering-colormap>` to the original colormap's
# name.

##############################################################################
# .. _registering-colormap:
#
# Registering a colormap
# ======================
#
# Colormaps can be added to the `matplotlib.colormaps` list of named colormaps.
# This allows the colormaps to be accessed by name in plotting functions:

# my_cmap, my_cmap_r from reversing a colormap
mpl.colormaps.register(cmap=my_cmap)
mpl.colormaps.register(cmap=my_cmap_r)

data = [[1, 2, 3, 4, 5]]

fig, (ax1, ax2) = plt.subplots(nrows=2)

ax1.imshow(data, cmap='my_cmap')
ax2.imshow(data, cmap='my_cmap_r')

plt.show()

#############################################################################
#
# .. admonition:: References
Expand Down