matplotlib.cm

Builtin colormaps, colormap handling utilities, and the ScalarMappable mixin.

See also

Colormap reference for a list of builtin colormaps.

Creating Colormaps in Matplotlib for examples of how to make colormaps.

Choosing Colormaps in Matplotlib an in-depth discussion of choosing colormaps.

Colormap normalization for more details about data normalization.

class matplotlib.cm.ColormapRegistry(cmaps)

Bases: Mapping

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 Colormaps:

import matplotlib as mpl
cmap = mpl.colormaps['viridis']

Returned Colormaps 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)

To get a list of all registered colormaps, you can do:

from matplotlib import colormaps
list(colormaps)

get_cmap(cmap)

Return a color map specified through cmap.

Parameters:

cmapstr or Colormap or None

• if a Colormap, return it

• if a string, look it up in mpl.colormaps

• if None, return the Colormap defined in rcParams["image.cmap"] (default: 'viridis')

Returns:

Colormap

register(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:

cmapmatplotlib.colors.Colormap

The colormap to register.

namestr, optional

The name for the colormap. If not given, cmap.name is used.

forcebool, 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.

unregister(name)

Remove a colormap from the registry.

You cannot remove built-in colormaps.

If the named colormap is not registered, returns with no error, raises if you try to de-register a default colormap.

Warning

Colormap names are currently a shared namespace that may be used by multiple packages. Use unregister only if you know you have registered that name before. In particular, do not unregister just in case to clean the name before registering a new colormap.

Parameters:

namestr

The name of the colormap to be removed.

Raises:

ValueError

If you try to remove a default built-in colormap.

matplotlib.cm.get_cmap(name=None, lut=None)

[Deprecated] Get a colormap instance, defaulting to rc values if name is None.

Parameters:

nameColormap or str or None, default: None

If a Colormap instance, it will be returned. Otherwise, the name of a colormap known to Matplotlib, which will be resampled by lut. The default, None, means rcParams["image.cmap"] (default: 'viridis').

lutint or None, default: None

If name is not already a Colormap instance and lut is not None, the colormap will be resampled to have lut entries in the lookup table.

Returns:

Colormap

Notes

Deprecated since version 3.7: Use matplotlib.colormaps[name] or matplotlib.colormaps.get_cmap() or pyplot.get_cmap() instead.

class matplotlib.cm.ScalarMappable(colorizer, **kwargs)

autoscale(self)

Autoscale the scalar limits on the norm instance using the current array

autoscale_None(self)

Autoscale the scalar limits on the norm instance using the current array, changing only limits that are None

changed(self)

Call this whenever the mappable is changed to notify all the callbackSM listeners to the 'changed' signal.

colorbar

The last colorbar associated with this ScalarMappable. May be None.

get_alpha(self)

get_array(self)

Return the array of values, that are mapped to colors.

The base class ScalarMappable does not make any assumptions on the dimensionality and shape of the array.

get_clim(self)

Return the values (min, max) that are mapped to the colormap limits.

get_cmap(self)

Return the Colormap instance.

property norm

set_array(self, A)

Set the value array from array-like A.

Parameters:

Aarray-like or None

The values that are mapped to colors.

The base class ScalarMappable does not make any assumptions on the dimensionality and shape of the value array A.

set_clim(self, vmin=None, vmax=None)

Set the norm limits for image scaling.

Parameters:

vmin, vmaxfloat

The limits.

For scalar data, the limits may also be passed as a tuple (vmin, vmax) as a single positional argument.

set_cmap(self, cmap)

Set the colormap for luminance data.

Parameters:

cmapColormap or str or None

set_norm(self, norm)

Set the normalization instance.

Parameters:

normNormalize or str or None

Notes

If there are any colorbars using the mappable for this norm, setting the norm of the mappable will reset the norm, locator, and formatters on the colorbar to default.

to_rgba(self, x, alpha=None, bytes=False, norm=True)

Return a normalized RGBA array corresponding to x.

In the normal case, x is a 1D or 2D sequence of scalars, and the corresponding ndarray of RGBA values will be returned, based on the norm and colormap set for this Colorizer.

There is one special case, for handling images that are already RGB or RGBA, such as might have been read from an image file. If x is an ndarray with 3 dimensions, and the last dimension is either 3 or 4, then it will be treated as an RGB or RGBA array, and no mapping will be done. The array can be uint8, or it can be floats with values in the 0-1 range; otherwise a ValueError will be raised. Any NaNs or masked elements will be set to 0 alpha. If the last dimension is 3, the alpha kwarg (defaulting to 1) will be used to fill in the transparency. If the last dimension is 4, the alpha kwarg is ignored; it does not replace the preexisting alpha. A ValueError will be raised if the third dimension is other than 3 or 4.

In either case, if bytes is False (default), the RGBA array will be floats in the 0-1 range; if it is True, the returned RGBA array will be uint8 in the 0 to 255 range.

If norm is False, no normalization of the input data is performed, and it is assumed to be in the range (0-1).