diff --git a/.flake8 b/.flake8
index 2d16a348e734..06ad576c1b19 100644
--- a/.flake8
+++ b/.flake8
@@ -45,7 +45,7 @@ per-file-ignores =
setupext.py: E501
tests.py: F401
- lib/matplotlib/__init__.py: F401
+ lib/matplotlib/__init__.py: E402, F401
lib/matplotlib/_api/__init__.py: F401
lib/matplotlib/_cm.py: E122, E202, E203, E302
lib/matplotlib/_mathtext.py: E221, E251
diff --git a/doc/api/matplotlib_configuration_api.rst b/doc/api/matplotlib_configuration_api.rst
index 5fa27bbc6723..3636c45d0c71 100644
--- a/doc/api/matplotlib_configuration_api.rst
+++ b/doc/api/matplotlib_configuration_api.rst
@@ -52,6 +52,12 @@ Logging
.. autofunction:: set_loglevel
+Colormaps
+=========
+
+.. autodata:: colormaps
+ :no-value:
+
Miscellaneous
=============
diff --git a/doc/users/next_whats_new/colormaps.rst b/doc/users/next_whats_new/colormaps.rst
new file mode 100644
index 000000000000..5262fab305da
--- /dev/null
+++ b/doc/users/next_whats_new/colormaps.rst
@@ -0,0 +1,18 @@
+Colormap registry
+------------------
+
+Colormaps are now managed via `matplotlib.colormaps`, which is a
+`.ColormapRegistry`.
+
+Colormaps can be obtained using item access::
+
+ import matplotlib as mpl
+ cmap = mpl.colormaps['viridis']
+
+To register new colormaps use::
+
+ mpl.colormaps.register(my_colormap)
+
+The use of `matplotlib.cm.get_cmap` and `matplotlib.cm.register_cmap` is
+discouraged in favor of the above. Within `.pyplot` the use of
+``plt.get_cmap()`` and ``plt.register_cmap()`` will continue to be supported.
\ No newline at end of file
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
index a62ab3e5cc46..ca66f5a53ed9 100644
--- a/lib/matplotlib/__init__.py
+++ b/lib/matplotlib/__init__.py
@@ -1445,3 +1445,8 @@ def inner(ax, *args, data=None, **kwargs):
_log.debug('interactive is %s', is_interactive())
_log.debug('platform is %s', sys.platform)
_log.debug('loaded modules: %s', list(sys.modules))
+
+
+# workaround: we must defer colormaps import to after loading rcParams, because
+# colormap creation depends on rcParams
+from matplotlib.cm import _colormaps as colormaps
diff --git a/lib/matplotlib/cm.py b/lib/matplotlib/cm.py
index 6d05be943b33..a44e1579b88b 100644
--- a/lib/matplotlib/cm.py
+++ b/lib/matplotlib/cm.py
@@ -15,7 +15,7 @@
normalization.
"""
-from collections.abc import MutableMapping
+from collections.abc import Mapping, MutableMapping
import numpy as np
from numpy import ma
@@ -91,13 +91,86 @@ def _warn_deprecated(self):
)
+class ColormapRegistry(Mapping):
+ r"""
+ Container for colormaps that are known to Matplotlib by name.
+
+ The universal registry instance is `matplotlib.colormaps`. There should be
+ no need for users to instantiate `.ColormapRegistry` themselves.
+
+ Read access uses a dict-like interface mapping names to `.Colormap`\s::
+
+ import matplotlib as mpl
+ cmap = mpl.colormaps['viridis']
+
+ Returned `.Colormap`\s are copies, so that their modification does not
+ change the global definition of the colormap.
+
+ Additional colormaps can be added via `.ColormapRegistry.register`::
+
+ mpl.colormaps.register(my_colormap)
+ """
+ def __init__(self, cmaps):
+ self._cmaps = cmaps
+
+ def __getitem__(self, item):
+ try:
+ return self._cmaps[item].copy()
+ except KeyError:
+ raise KeyError(f"{item!r} is not a known colormap name")
+
+ def __iter__(self):
+ return iter(self._cmaps)
+
+ def __len__(self):
+ return len(self._cmaps)
+
+ def __str__(self):
+ return ('ColormapRegistry; available colormaps:\n' +
+ ', '.join(f"'{name}'" for name in self))
+
+ def register(self, cmap, *, name=None, force=False):
+ """
+ Register a new colormap.
+
+ The colormap name can then be used as a string argument to any ``cmap``
+ parameter in Matplotlib. It is also available in ``pyplot.get_cmap``.
+
+ The colormap registry stores a copy of the given colormap, so that
+ future changes to the original colormap instance do not affect the
+ registered colormap. Think of this as the registry taking a snapshot
+ of the colormap at registration.
+
+ Parameters
+ ----------
+ cmap : matplotlib.colors.Colormap
+ The colormap to register.
+
+ name : str, optional
+ The name for the colormap. If not given, ``cmap.name`` is used.
+
+ force: bool, default: False
+ If False, a ValueError is raised if trying to overwrite an already
+ registered name. True supports overwriting registered colormaps
+ other than the builtin colormaps.
+ """
+ name = name or cmap.name
+ if name in self and not force:
+ raise ValueError(
+ f'A colormap named "{name}" is already registered.')
+ register_cmap(name, cmap.copy())
+
+
_cmap_registry = _gen_cmap_registry()
globals().update(_cmap_registry)
# This is no longer considered public API
cmap_d = _DeprecatedCmapDictWrapper(_cmap_registry)
__builtin_cmaps = tuple(_cmap_registry)
-# Continue with definitions ...
+# public acces to the colormaps should be via `matplotlib.colormaps`. For now,
+# we still create the registry here, but that should stay an implementation
+# detail.
+_colormaps = ColormapRegistry(_cmap_registry)
def register_cmap(name=None, cmap=None, *, override_builtin=False):
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