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Make ListedColormap.monochrome a property #29125

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Merged
merged 1 commit into from
Nov 13, 2024
Merged

Make ListedColormap.monochrome a property #29125

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20 changes: 15 additions & 5 deletions lib/matplotlib/colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1191,17 +1191,13 @@ class ListedColormap(Colormap):
the list will be extended by repetition.
"""
def __init__(self, colors, name='from_list', N=None):
self.monochrome = False # Are all colors identical? (for contour.py)
if N is None:
self.colors = colors
N = len(colors)
else:
if isinstance(colors, str):
self.colors = [colors] * N
self.monochrome = True
elif np.iterable(colors):
if len(colors) == 1:
self.monochrome = True
self.colors = list(
itertools.islice(itertools.cycle(colors), N))
else:
Expand All @@ -1211,7 +1207,6 @@ def __init__(self, colors, name='from_list', N=None):
pass
else:
self.colors = [gray] * N
self.monochrome = True
super().__init__(name, N)

def _init(self):
Expand All @@ -1220,6 +1215,21 @@ def _init(self):
self._isinit = True
self._set_extremes()

@property
def monochrome(self):
"""Return whether all colors in the colormap are identical."""
# Replacement for the attribute *monochrome*. This ensures a consistent
# response independent of the way the ListedColormap was created, which
# was not the case for the manually set attribute.
#
# TODO: It's a separate discussion whether we need this property on
# colormaps at all (at least as public API). It's a very special edge
# case and we only use it for contours internally.
if not self._isinit:
self._init()

return self.N <= 1 or np.all(self._lut[0] == self._lut[1:self.N])

def resampled(self, lutsize):
"""Return a new colormap with *lutsize* entries."""
colors = self(np.linspace(0, 1, lutsize))
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3 changes: 2 additions & 1 deletion lib/matplotlib/colors.pyi
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Expand Up @@ -130,11 +130,12 @@ class LinearSegmentedColormap(Colormap):
def reversed(self, name: str | None = ...) -> LinearSegmentedColormap: ...

class ListedColormap(Colormap):
monochrome: bool
colors: ArrayLike | ColorType
def __init__(
self, colors: ArrayLike | ColorType, name: str = ..., N: int | None = ...
) -> None: ...
@property
def monochrome(self) -> bool: ...
def resampled(self, lutsize: int) -> ListedColormap: ...
def reversed(self, name: str | None = ...) -> ListedColormap: ...

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6 changes: 6 additions & 0 deletions lib/matplotlib/tests/test_colors.py
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Expand Up @@ -74,6 +74,12 @@ def test_resampled():
assert_array_almost_equal(lc(np.nan), lc3(np.nan))


def test_monochrome():
assert mcolors.ListedColormap(["red"]).monochrome
assert mcolors.ListedColormap(["red"] * 5).monochrome
assert not mcolors.ListedColormap(["red", "green"]).monochrome


def test_colormaps_get_cmap():
cr = mpl.colormaps

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