"""

*****************

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. | |

+--------------------------------------+--------------------------------------+

.. _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

from matplotlib.patches import Rectangle

import numpy as np

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

# :doc:`/tutorials/intermediate/color_cycle` section contains additional

# information about controlling colors and style properties.

import numpy as np

import matplotlib.pyplot as plt

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('style: {!r}'.format(sty), 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()