diff --git a/lib/matplotlib/cm.py b/lib/matplotlib/cm.py
index 7e46cf567f70..e9a7aad6c456 100644
--- a/lib/matplotlib/cm.py
+++ b/lib/matplotlib/cm.py
@@ -328,7 +328,7 @@ def to_rgba(self, x, alpha=None, bytes=False, norm=True):
treated as an RGB or RGBA array, and no mapping will be done.
The array can be `~numpy.uint8`, or it can be floats with
values in the 0-1 range; otherwise a ValueError will be raised.
- If it is a masked array, any masked elements will be set to 0 alpha.
+ Any NaNs or masked elements will be set to 0 alpha.
If the last dimension is 3, the *alpha* kwarg (defaulting to 1)
will be used to fill in the transparency. If the last dimension
is 4, the *alpha* kwarg is ignored; it does not
@@ -360,6 +360,12 @@ def to_rgba(self, x, alpha=None, bytes=False, norm=True):
else:
raise ValueError("Third dimension must be 3 or 4")
if xx.dtype.kind == 'f':
+ # If any of R, G, B, or A is nan, set to 0
+ if np.any(nans := np.isnan(x)):
+ if xx.shape[2] == 4:
+ xx = xx.copy()
+ xx[np.any(nans, axis=2), :] = 0
+
if norm and (xx.max() > 1 or xx.min() < 0):
raise ValueError("Floating point image RGB values "
"must be in the 0..1 range.")
diff --git a/lib/matplotlib/tests/test_colors.py b/lib/matplotlib/tests/test_colors.py
index 2d71fea83472..5b5332100c2a 100644
--- a/lib/matplotlib/tests/test_colors.py
+++ b/lib/matplotlib/tests/test_colors.py
@@ -1352,6 +1352,32 @@ def test_scalarmappable_to_rgba(bytes):
np.testing.assert_almost_equal(sm.to_rgba(xm[..., :3], bytes=bytes), expected)
+@pytest.mark.parametrize("bytes", (True, False))
+def test_scalarmappable_nan_to_rgba(bytes):
+ sm = cm.ScalarMappable()
+
+ # RGBA
+ x = np.ones((2, 3, 4), dtype=float) * 0.5
+ x[0, 0, 0] = np.nan
+ expected = x.copy()
+ expected[0, 0, :] = 0
+ if bytes:
+ expected = (expected * 255).astype(np.uint8)
+ np.testing.assert_almost_equal(sm.to_rgba(x, bytes=bytes), expected)
+ assert np.any(np.isnan(x)) # Input array should not be changed
+
+ # RGB
+ expected[..., 3] = 255 if bytes else 1
+ expected[0, 0, 3] = 0
+ np.testing.assert_almost_equal(sm.to_rgba(x[..., :3], bytes=bytes), expected)
+ assert np.any(np.isnan(x)) # Input array should not be changed
+
+ # Out-of-range fail
+ x[1, 0, 0] = 42
+ with pytest.raises(ValueError, match='0..1 range'):
+ sm.to_rgba(x[..., :3], bytes=bytes)
+
+
def test_failed_conversions():
with pytest.raises(ValueError):
mcolors.to_rgba('5')
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