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New textcolor kwarg for legend #15898

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May 5, 2020
Merged

New textcolor kwarg for legend #15898

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16 changes: 16 additions & 0 deletions doc/users/next_whats_new/2019-12-09-legend-labelcolor.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
Text color for legend labels
----------------------------

The text color of legend labels can now be set by passing a parameter
``labelcolor`` to `~.axes.Axes.legend`. The ``labelcolor`` keyword can be:

* A single color (either a string or RGBA tuple), which adjusts the text color
of all the labels.
* A list or tuple, allowing the text color of each label to be set
individually.
* ``linecolor``, which sets the text color of each label to match the
corresponding line color.
* ``markerfacecolor``, which sets the text color of each label to match the
corresponding marker face color.
* ``markeredgecolor``, which sets the text color of each label to match the
corresponding marker edge color.
42 changes: 40 additions & 2 deletions lib/matplotlib/legend.py
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Expand Up @@ -21,13 +21,14 @@
information.
"""

import itertools
import logging
import time

import numpy as np

import matplotlib as mpl
from matplotlib import cbook, docstring
from matplotlib import cbook, docstring, colors
from matplotlib.artist import Artist, allow_rasterization
from matplotlib.cbook import silent_list
from matplotlib.font_manager import FontProperties
Expand Down Expand Up @@ -172,6 +173,12 @@ def _update_bbox_to_anchor(self, loc_in_canvas):
absolute font size in points. String values are relative to the current
default font size. This argument is only used if *prop* is not specified.

labelcolor : str or list
Sets the color of the text in the legend. Can be a valid color string
(for example, 'red'), or a list of color strings. The labelcolor can
also be made to match the color of the line or marker using 'linecolor',
'markerfacecolor' (or 'mfc'), or 'markeredgecolor' (or 'mec').

numpoints : int, default: :rc:`legend.numpoints`
The number of marker points in the legend when creating a legend
entry for a `.Line2D` (line).
Expand Down Expand Up @@ -293,7 +300,8 @@ def __init__(self, parent, handles, labels,
scatterpoints=None, # number of scatter points
scatteryoffsets=None,
prop=None, # properties for the legend texts
fontsize=None, # keyword to set font size directly
fontsize=None, # keyword to set font size directly
labelcolor=None, # keyword to set the text color

# spacing & pad defined as a fraction of the font-size
borderpad=None, # the whitespace inside the legend border
Expand Down Expand Up @@ -505,6 +513,36 @@ def __init__(self, parent, handles, labels,
self.set_title(title, prop=tprop)
self._draggable = None

# set the text color

color_getters = { # getter function depends on line or patch
'linecolor': ['get_color', 'get_facecolor'],
'markerfacecolor': ['get_markerfacecolor', 'get_facecolor'],
'mfc': ['get_markerfacecolor', 'get_facecolor'],
'markeredgecolor': ['get_markeredgecolor', 'get_edgecolor'],
'mec': ['get_markeredgecolor', 'get_edgecolor'],
}
if labelcolor is None:
pass
elif isinstance(labelcolor, str) and labelcolor in color_getters:
getter_names = color_getters[labelcolor]
for handle, text in zip(self.legendHandles, self.texts):
for getter_name in getter_names:
try:
color = getattr(handle, getter_name)()
text.set_color(color)
break
except AttributeError:
pass
elif np.iterable(labelcolor):
for text, color in zip(self.texts,
itertools.cycle(
colors.to_rgba_array(labelcolor))):
text.set_color(color)
else:
raise ValueError("Invalid argument for labelcolor : %s" %
str(labelcolor))

def _set_artist_props(self, a):
"""
Set the boilerplate props for artists added to axes.
Expand Down
60 changes: 60 additions & 0 deletions lib/matplotlib/tests/test_legend.py
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Expand Up @@ -534,6 +534,66 @@ def test_legend_title_fontsize():
assert leg.get_title().get_fontsize() == 22


def test_legend_labelcolor_single():
# test labelcolor for a single color
fig, ax = plt.subplots()
ax.plot(np.arange(10), np.arange(10)*1, label='#1')
ax.plot(np.arange(10), np.arange(10)*2, label='#2')
ax.plot(np.arange(10), np.arange(10)*3, label='#3')

leg = ax.legend(labelcolor='red')
for text in leg.get_texts():
assert mpl.colors.same_color(text.get_color(), 'red')


def test_legend_labelcolor_list():
# test labelcolor for a list of colors
fig, ax = plt.subplots()
ax.plot(np.arange(10), np.arange(10)*1, label='#1')
ax.plot(np.arange(10), np.arange(10)*2, label='#2')
ax.plot(np.arange(10), np.arange(10)*3, label='#3')

leg = ax.legend(labelcolor=['r', 'g', 'b'])
for text, color in zip(leg.get_texts(), ['r', 'g', 'b']):
assert mpl.colors.same_color(text.get_color(), color)


def test_legend_labelcolor_linecolor():
# test the labelcolor for labelcolor='linecolor'
fig, ax = plt.subplots()
ax.plot(np.arange(10), np.arange(10)*1, label='#1', color='r')
ax.plot(np.arange(10), np.arange(10)*2, label='#2', color='g')
ax.plot(np.arange(10), np.arange(10)*3, label='#3', color='b')

leg = ax.legend(labelcolor='linecolor')
for text, color in zip(leg.get_texts(), ['r', 'g', 'b']):
assert mpl.colors.same_color(text.get_color(), color)


def test_legend_labelcolor_markeredgecolor():
# test the labelcolor for labelcolor='markeredgecolor'
fig, ax = plt.subplots()
ax.plot(np.arange(10), np.arange(10)*1, label='#1', markeredgecolor='r')
ax.plot(np.arange(10), np.arange(10)*2, label='#2', markeredgecolor='g')
ax.plot(np.arange(10), np.arange(10)*3, label='#3', markeredgecolor='b')

leg = ax.legend(labelcolor='markeredgecolor')
for text, color in zip(leg.get_texts(), ['r', 'g', 'b']):
assert mpl.colors.same_color(text.get_color(), color)


def test_legend_labelcolor_markerfacecolor():
# test the labelcolor for labelcolor='markerfacecolor'
fig, ax = plt.subplots()
ax.plot(np.arange(10), np.arange(10)*1, label='#1', markerfacecolor='r')
ax.plot(np.arange(10), np.arange(10)*2, label='#2', markerfacecolor='g')
ax.plot(np.arange(10), np.arange(10)*3, label='#3', markerfacecolor='b')

leg = ax.legend(labelcolor='markerfacecolor')
for text, color in zip(leg.get_texts(), ['r', 'g', 'b']):
assert mpl.colors.same_color(text.get_color(), color)


def test_get_set_draggable():
legend = plt.legend()
assert not legend.get_draggable()
Expand Down