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"""
.. _colormap_example:
Colormap Choices
~~~~~~~~~~~~~~~~
Use a Matplotlib, Colorcet, cmocean, or custom colormap when plotting scalar
values.
"""
from __future__ import annotations
from matplotlib.colors import ListedColormap
import matplotlib.pyplot as plt
import numpy as np
import pyvista as pv
from pyvista import examples
# %%
# Any colormap built for ``matplotlib``, ``colorcet``, or ``cmocean`` is fully
# compatible with PyVista. Colormaps are typically specified by passing the
# string name of the colormap to the plotting routine via the ``cmap``
# argument.
#
# See `Matplotlib's complete list of available colormaps`_,
# `Colorcet's complete list`_, and `cmocean's complete list`_.
#
# .. _Matplotlib's complete list of available colormaps: https://matplotlib.org/tutorials/colors/colormaps.html
# .. _Colorcet's complete list: https://colorcet.holoviz.org/user_guide/index.html
# .. _cmocean's complete list: https://matplotlib.org/cmocean/
# %%
# Custom Made Colormaps
# +++++++++++++++++++++
#
# To get started using a custom colormap, download some data with scalar values to
# plot.
mesh = examples.download_st_helens().warp_by_scalar()
# Add scalar array with range (0, 100) that correlates with elevation
mesh['values'] = pv.plotting.tools.normalize(mesh['Elevation']) * 100
# %%
# Build a custom colormap - here we make a colormap with 5 discrete colors
# and we specify the ranges where those colors fall:
# Define the colors we want to use
blue = np.array([12 / 256, 238 / 256, 246 / 256, 1.0])
black = np.array([11 / 256, 11 / 256, 11 / 256, 1.0])
grey = np.array([189 / 256, 189 / 256, 189 / 256, 1.0])
yellow = np.array([255 / 256, 247 / 256, 0 / 256, 1.0])
red = np.array([1.0, 0.0, 0.0, 1.0])
mapping = np.linspace(mesh['values'].min(), mesh['values'].max(), 256)
newcolors = np.empty((256, 4))
newcolors[mapping >= 80] = red
newcolors[mapping < 80] = grey
newcolors[mapping < 55] = yellow
newcolors[mapping < 30] = blue
newcolors[mapping < 1] = black
# Make the colormap from the listed colors
my_colormap = ListedColormap(newcolors)
# %%
# Simply pass the colormap to the plotting routine.
mesh.plot(scalars='values', cmap=my_colormap)
# %%
# Or you could make a simple colormap... any Matplotlib colormap can be passed
# to PyVista.
boring_cmap = plt.get_cmap("viridis", 5)
mesh.plot(scalars='values', cmap=boring_cmap)
# %%
# You can also pass a list of color strings to the color map. This
# approach divides up the colormap into 5 equal parts.
mesh.plot(scalars=mesh['values'], cmap=['black', 'blue', 'yellow', 'grey', 'red'])
# %%
# If you still wish to have control of the separation of values, you
# can do this by creating a scalar array and passing that to the
# plotter along with the colormap
scalars = np.empty(mesh.n_points)
scalars[mesh['values'] >= 80] = 4 # red
scalars[mesh['values'] < 80] = 3 # grey
scalars[mesh['values'] < 55] = 2 # yellow
scalars[mesh['values'] < 30] = 1 # blue
scalars[mesh['values'] < 1] = 0 # black
mesh.plot(scalars=scalars, cmap=['black', 'blue', 'yellow', 'grey', 'red'])
# %%
# Matplotlib vs. Colorcet
# +++++++++++++++++++++++
#
# Let's compare Colorcet's perceptually uniform "fire" colormap to Matplotlib's
# "hot" colormap much like the example on the `first page of Colorcet's docs`_.
#
# .. _first page of Colorcet's docs: https://colorcet.holoviz.org/index.html
#
# The "hot" version washes out detail at the high end, as if the image is
# overexposed, while "fire" makes detail visible throughout the data range.
#
# Please note that in order to use Colorcet's colormaps including "fire", you
# must have Colorcet installed in your Python environment:
# ``pip install colorcet``
p = pv.Plotter(shape=(2, 2), border=False)
p.subplot(0, 0)
p.add_mesh(
mesh,
scalars='Elevation',
cmap="fire",
lighting=True,
scalar_bar_args={'title': "Colorcet Fire"},
)
p.subplot(0, 1)
p.add_mesh(
mesh,
scalars='Elevation',
cmap="fire",
lighting=False,
scalar_bar_args={'title': "Colorcet Fire (No Lighting)"},
)
p.subplot(1, 0)
p.add_mesh(
mesh,
scalars='Elevation',
cmap="hot",
lighting=True,
scalar_bar_args={'title': "Matplotlib Hot"},
)
p.subplot(1, 1)
p.add_mesh(
mesh,
scalars='Elevation',
cmap="hot",
lighting=False,
scalar_bar_args={'title': "Matplotlib Hot (No Lighting)"},
)
p.show()
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