fix(plot): use matplotlib colormaps registry instead of removed cm.get_cmap

src/roboticstoolbox/mobile/DistanceTransformPlanner.py

@@ -9,7 +9,7 @@
 from spatialmath import base
 from scipy.ndimage import *
 import matplotlib.pyplot as plt
-from matplotlib import cm
+from matplotlib import colormaps
 from roboticstoolbox.mobile.PlannerBase import PlannerBase
 
 
@@ -324,9 +324,7 @@ def distancexform(occgrid, goal, metric="cityblock", animate=False, summary=Fals
                 plt.ylabel("y")
                 ax = plt.gca()
                 plt.pause(0.001)
-                cmap = cm.get_cmap("gray")
-                cmap.set_bad("red")
-                cmap.set_over("white")
+                cmap = colormaps.get_cmap("gray").with_extremes(bad="red", over="white")
                 h = plt.imshow(display, cmap=cmap)
                 plt.colorbar(label="distance")
             else:

src/roboticstoolbox/robot/RobotPlottingMPL.py

@@ -62,12 +62,12 @@ def linkcolormap(self, linkcolors: list[Any] | str = "viridis"):
 
         """
 
-        from matplotlib import cm, colors
+        from matplotlib import colormaps, colors
 
-        if isinstance(linkcolors, list) and len(linkcolors) == self.n:  # type: ignore[attr-defined]  # pragma: nocover
+        if isinstance(linkcolors, list) and len(linkcolors) == self.n:  # type: ignore[attr-defined]
             return colors.ListedColormap(linkcolors)
-        else:  # pragma: nocover
-            return cm.get_cmap(linkcolors, 6)  # type: ignore[arg-type]
+        else:
+            return colormaps.get_cmap(linkcolors).resampled(6)
 
     # ------------------------------------------------------------------
     # Ellipse creation

tests/test_backend_capabilities.py

@@ -112,6 +112,20 @@ def test_robot_has_linkcolormap(self):
         robot = self._make_robot()
         self.assertTrue(hasattr(robot, "linkcolormap"))
 
+    def test_linkcolormap_from_name(self):
+        # Regression test: linkcolormap() used matplotlib.cm.get_cmap(),
+        # removed in matplotlib 3.9, so any named colormap raised
+        # AttributeError instead of returning a 6-entry colormap.
+        robot = self._make_robot()
+        cmap = robot.linkcolormap("inferno")
+        self.assertEqual(cmap.N, 6)
+
+    def test_linkcolormap_from_list(self):
+        robot = self._make_robot()
+        colors = ["red", "g", (0, 0.5, 0), "#0f8040", "yellow", "cyan"]
+        cmap = robot.linkcolormap(colors)
+        self.assertEqual(cmap.N, len(colors))
+
     def test_mixin_present_in_mro(self):
         import roboticstoolbox as rtb
         from roboticstoolbox.robot.RobotPlottingMPL import RobotPlottingMPLMixin

tests/test_distance_transform_plot.py

@@ -25,3 +25,17 @@ def test_distance_transform_next_before_plan_raises():
 
     with pytest.raises(ValueError, match="No distance map computed"):
         planner.next((0, 0))
+
+
+def test_distancexform_animate():
+    # Regression test: the animate path used matplotlib.cm.get_cmap(),
+    # removed in matplotlib 3.9, so plan(animate=True) raised
+    # AttributeError before computing the distance map.
+    floorplan = np.zeros((10, 10), dtype=int)
+    floorplan[4:7, 4:7] = 1
+
+    planner = rtb.DistanceTransformPlanner(floorplan, inflate=1)
+    planner.plan((8, 8), animate=True)
+
+    assert planner.distancemap is not None
+    plt.close("all")