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"""
.. redirect-from:: /tutorials/colors/colors
.. _colors_def:
*****************
Specifying colors
*****************
Color formats
=============
Matplotlib recognizes the following formats to specify a color.
+--------------------------------------+--------------------------------------+
| Format | Example |
+======================================+======================================+
| RGB or RGBA (red, green, blue, alpha)| - ``(0.1, 0.2, 0.5)`` |
| tuple of float values in a closed | - ``(0.1, 0.2, 0.5, 0.3)`` |
| interval [0, 1]. | |
+--------------------------------------+--------------------------------------+
| Case-insensitive hex RGB or RGBA | - ``'#0f0f0f'`` |
| string. | - ``'#0f0f0f80'`` |
+--------------------------------------+--------------------------------------+
| Case-insensitive RGB or RGBA string | - ``'#abc'`` as ``'#aabbcc'`` |
| equivalent hex shorthand of | - ``'#fb1'`` as ``'#ffbb11'`` |
| duplicated characters. | |
+--------------------------------------+--------------------------------------+
| String representation of float value | - ``'0'`` as black |
| in closed interval ``[0, 1]`` for | - ``'1'`` as white |
| grayscale values. | - ``'0.8'`` as light gray |
+--------------------------------------+--------------------------------------+
| Single character shorthand notation | - ``'b'`` as blue |
| for some basic colors. | - ``'g'`` as green |
| | - ``'r'`` as red |
| .. note:: | - ``'c'`` as cyan |
| The colors green, cyan, magenta, | - ``'m'`` as magenta |
| and yellow do not coincide with | - ``'y'`` as yellow |
| X11/CSS4 colors. Their particular | - ``'k'`` as black |
| shades were chosen for better | - ``'w'`` as white |
| visibility of colored lines | |
| against typical backgrounds. | |
+--------------------------------------+--------------------------------------+
| Case-insensitive X11/CSS4 color name | - ``'aquamarine'`` |
| with no spaces. | - ``'mediumseagreen'`` |
+--------------------------------------+--------------------------------------+
| Case-insensitive color name from | - ``'xkcd:sky blue'`` |
| `xkcd color survey`_ with ``'xkcd:'``| - ``'xkcd:eggshell'`` |
| prefix. | |
+--------------------------------------+--------------------------------------+
| Case-insensitive Tableau Colors from | - ``'tab:blue'`` |
| 'T10' categorical palette. | - ``'tab:orange'`` |
| | - ``'tab:green'`` |
| | - ``'tab:red'`` |
| | - ``'tab:purple'`` |
| .. note:: This is the default color | - ``'tab:brown'`` |
| cycle. | - ``'tab:pink'`` |
| | - ``'tab:gray'`` |
| | - ``'tab:olive'`` |
| | - ``'tab:cyan'`` |
+--------------------------------------+--------------------------------------+
| "CN" color spec where ``'C'`` | - ``'C0'`` |
| precedes a number acting as an index | - ``'C1'`` |
| into the default property cycle. +--------------------------------------+
| | :rc:`axes.prop_cycle` |
| .. note:: Matplotlib indexes color | |
| at draw time and defaults | |
| to black if cycle does not | |
| include color. | |
+--------------------------------------+--------------------------------------+
| Tuple of one of the above color | - ``('green', 0.3)`` |
| formats and an alpha float. | - ``('#f00', 0.9)`` |
| | |
| .. versionadded:: 3.8 | |
+--------------------------------------+--------------------------------------+
| The special value "none" is fully | - ``'none'`` |
| transparent, i.e. equivalent to a | |
| RGBA value ``(0.0, 0.0, 0.0, 0.0)`` | |
+--------------------------------------+--------------------------------------+
.. _xkcd color survey: https://xkcd.com/color/rgb/
.. seealso::
The following links provide more information on colors in Matplotlib.
* :doc:`/gallery/color/color_demo` Example
* `matplotlib.colors` API
* :doc:`/gallery/color/named_colors` Example
"Red", "Green", and "Blue" are the intensities of those colors. In combination,
they represent the colorspace.
Transparency
============
The *alpha* value of a color specifies its transparency, where 0 is fully
transparent and 1 is fully opaque. When a color is semi-transparent, the
background color will show through.
The *alpha* value determines the resulting color by blending the
foreground color with the background color according to the formula
.. math::
RGB_{result} = RGB_{background} * (1 - \\alpha) + RGB_{foreground} * \\alpha
The following plot illustrates the effect of transparency.
"""
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.patches import Rectangle
fig, ax = plt.subplots(figsize=(6.5, 1.65), layout='constrained')
ax.add_patch(Rectangle((-0.2, -0.35), 11.2, 0.7, color='C1', alpha=0.8))
for i, alpha in enumerate(np.linspace(0, 1, 11)):
ax.add_patch(Rectangle((i, 0.05), 0.8, 0.6, alpha=alpha, zorder=0))
ax.text(i+0.4, 0.85, f"{alpha:.1f}", ha='center')
ax.add_patch(Rectangle((i, -0.05), 0.8, -0.6, alpha=alpha, zorder=2))
ax.set_xlim(-0.2, 13)
ax.set_ylim(-1, 1)
ax.set_title('alpha values')
ax.text(11.3, 0.6, 'zorder=1', va='center', color='C0')
ax.text(11.3, 0, 'zorder=2\nalpha=0.8', va='center', color='C1')
ax.text(11.3, -0.6, 'zorder=3', va='center', color='C0')
ax.axis('off')
# %%
#
# The orange rectangle is semi-transparent with *alpha* = 0.8. The top row of
# blue squares is drawn below and the bottom row of blue squares is drawn on
# top of the orange rectangle.
#
# See also :doc:`/gallery/misc/zorder_demo` to learn more on the drawing order.
#
#
# "CN" color selection
# ====================
#
# Matplotlib converts "CN" colors to RGBA when drawing Artists. The
# :ref:`color_cycle` section contains additional
# information about controlling colors and style properties.
import matplotlib.pyplot as plt
import numpy as np
import matplotlib as mpl
th = np.linspace(0, 2*np.pi, 128)
def demo(sty):
mpl.style.use(sty)
fig, ax = plt.subplots(figsize=(3, 3))
ax.set_title(f'style: {sty!r}', color='C0')
ax.plot(th, np.cos(th), 'C1', label='C1')
ax.plot(th, np.sin(th), 'C2', label='C2')
ax.legend()
demo('default')
demo('seaborn-v0_8')
# %%
# The first color ``'C0'`` is the title. Each plot uses the second and third
# colors of each style's :rc:`axes.prop_cycle`. They are ``'C1'`` and ``'C2'``,
# respectively.
#
# .. _xkcd-colors:
#
# Comparison between X11/CSS4 and xkcd colors
# ===========================================
#
# The xkcd colors come from a `user survey conducted by the webcomic xkcd
# <https://blog.xkcd.com/2010/05/03/color-survey-results/>`__.
#
# 95 out of the 148 X11/CSS4 color names also appear in the xkcd color survey.
# Almost all of them map to different color values in the X11/CSS4 and in
# the xkcd palette. Only 'black', 'white' and 'cyan' are identical.
#
# For example, ``'blue'`` maps to ``'#0000FF'`` whereas ``'xkcd:blue'`` maps to
# ``'#0343DF'``. Due to these name collisions, all xkcd colors have the
# ``'xkcd:'`` prefix.
#
# The visual below shows name collisions. Color names where color values agree
# are in bold.
import matplotlib.colors as mcolors
import matplotlib.patches as mpatch
overlap = {name for name in mcolors.CSS4_COLORS
if f'xkcd:{name}' in mcolors.XKCD_COLORS}
fig = plt.figure(figsize=[9, 5])
ax = fig.add_axes([0, 0, 1, 1])
n_groups = 3
n_rows = len(overlap) // n_groups + 1
for j, color_name in enumerate(sorted(overlap)):
css4 = mcolors.CSS4_COLORS[color_name]
xkcd = mcolors.XKCD_COLORS[f'xkcd:{color_name}'].upper()
# Pick text colour based on perceived luminance.
rgba = mcolors.to_rgba_array([css4, xkcd])
luma = 0.299 * rgba[:, 0] + 0.587 * rgba[:, 1] + 0.114 * rgba[:, 2]
css4_text_color = 'k' if luma[0] > 0.5 else 'w'
xkcd_text_color = 'k' if luma[1] > 0.5 else 'w'
col_shift = (j // n_rows) * 3
y_pos = j % n_rows
text_args = dict(fontsize=10, weight='bold' if css4 == xkcd else None)
ax.add_patch(mpatch.Rectangle((0 + col_shift, y_pos), 1, 1, color=css4))
ax.add_patch(mpatch.Rectangle((1 + col_shift, y_pos), 1, 1, color=xkcd))
ax.text(0.5 + col_shift, y_pos + .7, css4,
color=css4_text_color, ha='center', **text_args)
ax.text(1.5 + col_shift, y_pos + .7, xkcd,
color=xkcd_text_color, ha='center', **text_args)
ax.text(2 + col_shift, y_pos + .7, f' {color_name}', **text_args)
for g in range(n_groups):
ax.hlines(range(n_rows), 3*g, 3*g + 2.8, color='0.7', linewidth=1)
ax.text(0.5 + 3*g, -0.3, 'X11/CSS4', ha='center')
ax.text(1.5 + 3*g, -0.3, 'xkcd', ha='center')
ax.set_xlim(0, 3 * n_groups)
ax.set_ylim(n_rows, -1)
ax.axis('off')
plt.show()
|
