matplotlib
diff --git a/‎doc/users/next_whats_new/colormap_with_alpha
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diff --git a/‎lib/matplotlib/colors.py
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diff --git a/‎lib/matplotlib/colors.pyi
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diff --git a/‎lib/matplotlib/tests/test_colors.py
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@@ -0,0 +1,5 @@
+Tuning transparency of colormaps
+--------------------------------
+The new method `.Colormap.with_alpha` allows to create a new colormap with the same
+color values but a new uniform alpha value. This is handy if you want to modify only
+the transparency of mapped colors for an Artist.
@@ -943,6 +943,25 @@ def _set_extremes(self):
             self._lut[self._i_over] = self._lut[self.N - 1]
         self._lut[self._i_bad] = self._rgba_bad
 
+    def with_alpha(self, alpha):
+        """
+        Return a copy of the colormap with a new uniform transparency.
+
+        Parameters
+        ----------
+        alpha : float
+             The alpha blending value, between 0 (transparent) and 1 (opaque).
+        """
+        if not isinstance(alpha, Real):
+            raise TypeError(f"'alpha' must be numeric or None, not {type(alpha)}")
+        if not 0 <= alpha <= 1:
+            ValueError("'alpha' must be between 0 and 1, inclusive")
+        new_cm = self.copy()
+        if not new_cm._isinit:
+            new_cm._init()
+        new_cm._lut[:, 3] = alpha
+        return new_cm
+
     def _init(self):
         """Generate the lookup table, ``self._lut``."""
         raise NotImplementedError("Abstract class only")
 
@@ -111,6 +111,7 @@ class Colormap:
         under: ColorType | None = ...,
         over: ColorType | None = ...
     ) -> Colormap: ...
+    def with_alpha(self, alpha: float) -> Colormap: ...
     def is_gray(self) -> bool: ...
     def resampled(self, lutsize: int) -> Colormap: ...
     def reversed(self, name: str | None = ...) -> Colormap: ...
 
@@ -20,7 +20,7 @@
 import matplotlib.scale as mscale
 from matplotlib.rcsetup import cycler
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
-from matplotlib.colors import is_color_like, to_rgba_array
+from matplotlib.colors import is_color_like, to_rgba_array, ListedColormap
 
 
 @pytest.mark.parametrize('N, result', [
@@ -248,6 +248,17 @@ def test_LinearSegmentedColormap_from_list_bad_under_over():
     assert mcolors.same_color(cmap.get_over(), "y")
 
 
+def test_colormap_with_alpha():
+    cmap = ListedColormap(["red", "green", ("blue", 0.8)])
+    cmap2 = cmap.with_alpha(0.5)
+    # color is the same:
+    vals = [0, 0.5, 1]  # numeric positions that map to the listed colors
+    assert_array_equal(cmap(vals)[:, :3], cmap2(vals)[:, :3])
+    # alpha of cmap2 is changed:
+    assert_array_equal(cmap(vals)[:, 3], [1, 1, 0.8])
+    assert_array_equal(cmap2(vals)[:, 3], [0.5, 0.5, 0.5])
+
+
 def test_BoundaryNorm():
     """
     GitHub issue #1258: interpolation was failing with numpy