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ENH: Add Petroff 6 and 8 color cycle style sheets #30065

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May 19, 2025
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ENH: Add Petroff 6 and 8 color cycle style sheets #30065

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ENH: Add Petroff 6 and 8 color cycle style sheets
matthewfeickert May 18, 2025
324e7f9
TST: Add 6 and 8 color Petroff color sequences to tests
matthewfeickert May 18, 2025
b89e4ce
DOC: Add 'What's New' entry for 6 and 8 Petorff color cycles
matthewfeickert May 18, 2025
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21 changes: 21 additions & 0 deletions doc/users/next_whats_new/six_and_eight_color_petroff_color_cycles.rst
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@@ -0,0 +1,21 @@
Six and eight color Petroff color cycles
----------------------------------------

The six and eight color accessible Petroff color cycles are named 'petroff6' and
'petroff8'.
They compliment the existing 'petroff10' color cycle, added in `Matplotlib 3.10.0`_

For more details see
`Petroff, M. A.: "Accessible Color Sequences for Data Visualization"
<https://arxiv.org/abs/2107.02270>`_.
To load the 'petroff6' color cycle in place of the default::

import matplotlib.pyplot as plt
plt.style.use('petroff6')

or to load the 'petroff8' color cycle::

import matplotlib.pyplot as plt
plt.style.use('petroff8')

.. _Matplotlib 3.10.0: https://matplotlib.org/stable/users/prev_whats_new/whats_new_3.10.0.html#new-more-accessible-color-cycle
23 changes: 23 additions & 0 deletions lib/matplotlib/_cm.py
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The RGB values were determiend from converting the hex using https://www.rapidtables.com/convert/color/hex-to-rgb.html. If a more specific method is desired, I'm happy to double check the RGB values with it.

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I think this should do, since screens have much more difference between them than a single RGB color step anyway.

(Since I didn't know which was the original format, I did some conversions, thinking that the RGB was the approximation of the 0-1-range. And then read the paper to see that it was the other way around. It seems to match exactly.)

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This code will exactly convert the top-cycles.json file to the format here:

#!/usr/bin/env python3

import json

with open("top-cycles.json") as infile:
    cycles = json.load(infile)

for k in cycles:
    print(f"_petroff{k}_data = (")
    for c in cycles[k]:
        cf = [str(int(c[i * 2 : (i + 1) * 2], 16) / 255) for i in range(3)]
        print(f"    ({cf[0] + ',':20} {cf[1] + ',':20} {cf[2] + '),':22}  # {c}")
    print(")\n")

Original file line number Diff line number Diff line change
Expand Up @@ -1365,6 +1365,29 @@ def _gist_yarg(x): return 1 - x
(0.8509803921568627, 0.8509803921568627, 0.8509803921568627 ), # d9d9d9
)

# Colorblind accessible palettes from
# Matthew A. Petroff, Accessible Color Sequences for Data Visualization
# https://arxiv.org/abs/2107.02270

_petroff6_data = (
(0.3411764705882353, 0.5647058823529412, 0.9882352941176471), # 5790fc
(0.9725490196078431, 0.611764705882353, 0.12549019607843137), # f89c20
(0.8941176470588236, 0.1450980392156863, 0.21176470588235294), # e42536
(0.5882352941176471, 0.2901960784313726, 0.5450980392156862), # 964a8b
(0.611764705882353, 0.611764705882353, 0.6313725490196078), # 9c9ca1
(0.47843137254901963, 0.12941176470588237, 0.8666666666666667), # 7a21dd
)

_petroff8_data = (
(0.09411764705882353, 0.27058823529411763, 0.984313725490196), # 1845fb
(1.0, 0.3686274509803922, 0.00784313725490196), # ff5e02
(0.788235294117647, 0.12156862745098039, 0.08627450980392157), # c91f16
(0.7843137254901961, 0.28627450980392155, 0.6627450980392157), # c849a9
(0.6784313725490196, 0.6784313725490196, 0.49019607843137253), # adad7d
(0.5254901960784314, 0.7843137254901961, 0.8666666666666667), # 86c8dd
(0.3411764705882353, 0.5529411764705883, 1.0), # 578dff
(0.396078431372549, 0.38823529411764707, 0.39215686274509803), # 656364
)

_petroff10_data = (
(0.24705882352941178, 0.5647058823529412, 0.8549019607843137), # 3f90da
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2 changes: 2 additions & 0 deletions lib/matplotlib/colors.py
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Expand Up @@ -131,6 +131,8 @@ class ColorSequenceRegistry(Mapping):
'Set1': _cm._Set1_data,
'Set2': _cm._Set2_data,
'Set3': _cm._Set3_data,
'petroff6': _cm._petroff6_data,
'petroff8': _cm._petroff8_data,
'petroff10': _cm._petroff10_data,
}

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5 changes: 5 additions & 0 deletions lib/matplotlib/mpl-data/stylelib/petroff6.mplstyle
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# Color cycle survey palette from Petroff (2021):
# https://arxiv.org/abs/2107.02270
# https://github.com/mpetroff/accessible-color-cycles
axes.prop_cycle: cycler('color', ['5790fc', 'f89c20', 'e42536', '964a8b', '9c9ca1', '7a21dd'])
patch.facecolor: 5790fc
5 changes: 5 additions & 0 deletions lib/matplotlib/mpl-data/stylelib/petroff8.mplstyle
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# Color cycle survey palette from Petroff (2021):
# https://arxiv.org/abs/2107.02270
# https://github.com/mpetroff/accessible-color-cycles
axes.prop_cycle: cycler('color', ['1845fb', 'ff5e02', 'c91f16', 'c849a9', 'adad7d', '86c8dd', '578dff', '656364'])
patch.facecolor: 1845fb
3 changes: 2 additions & 1 deletion lib/matplotlib/tests/test_colors.py
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Expand Up @@ -1704,7 +1704,8 @@ def test_color_sequences():
assert plt.color_sequences is matplotlib.color_sequences # same registry
assert list(plt.color_sequences) == [
'tab10', 'tab20', 'tab20b', 'tab20c', 'Pastel1', 'Pastel2', 'Paired',
'Accent', 'Dark2', 'Set1', 'Set2', 'Set3', 'petroff10']
'Accent', 'Dark2', 'Set1', 'Set2', 'Set3', 'petroff6', 'petroff8',
'petroff10']
assert len(plt.color_sequences['tab10']) == 10
assert len(plt.color_sequences['tab20']) == 20

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