matplotlib · tacaswell · Jun 9, 2023 · Jun 4, 2023 · Jun 6, 2023
diff --git a/lib/matplotlib/backends/backend_ps.py b/lib/matplotlib/backends/backend_ps.py
@@ -697,6 +697,8 @@ def draw_gouraud_triangle(self, gc, points, colors, trans):
     @_log_if_debug_on
     def draw_gouraud_triangles(self, gc, points, colors, trans):
         assert len(points) == len(colors)
+        if len(points) == 0:
+            return
         assert points.ndim == 3
         assert points.shape[1] == 3
         assert points.shape[2] == 2

diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
@@ -2098,6 +2098,10 @@ def _convert_mesh_to_triangles(self, coordinates):
         ], axis=2).reshape((-1, 3, 2))
 
         c = self.get_facecolor().reshape((*coordinates.shape[:2], 4))
+        z = self.get_array()
+        mask = z.mask if np.ma.is_masked(z) else None
+        if mask is not None:
+            c[mask, 3] = np.nan
         c_a = c[:-1, :-1]
         c_b = c[:-1, 1:]
         c_c = c[1:, 1:]
@@ -2109,8 +2113,8 @@ def _convert_mesh_to_triangles(self, coordinates):
             c_c, c_d, c_center,
             c_d, c_a, c_center,
         ], axis=2).reshape((-1, 3, 4))
-
-        return triangles, colors
+        tmask = np.isnan(colors[..., 2, 3])
+        return triangles[~tmask], colors[~tmask]
 
     @artist.allow_rasterization
     def draw(self, renderer):

diff --git a/lib/matplotlib/tests/baseline_images/test_axes/pcolormesh.pdf b/lib/matplotlib/tests/baseline_images/test_axes/pcolormesh.pdf
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/pcolormesh.png b/lib/matplotlib/tests/baseline_images/test_axes/pcolormesh.png