Scope raster rc defaults (partial fix for map-utils compatibility)

ultraplot/axes/plot.py

@@ -7138,6 +7138,7 @@ def pcolorfast(self, x, y, z, **kwargs):
         %(plot.pcolorfast)s
         """
         x, y, z, kw = self._parse_2d_args(x, y, z, edges=True, **kwargs)
+        user_interpolation = "interpolation" in kw
         kw.update(_pop_props(kw, "collection"))
         center_levels = kw.pop("center_levels", None)
         kw = self._parse_cmap(
@@ -7148,6 +7149,8 @@ def pcolorfast(self, x, y, z, **kwargs):
         guide_kw = _pop_params(kw, self._update_guide)
         with self._keep_grid_bools():
             m = self._call_native("pcolorfast", x, y, z, **kw)
+        if isinstance(m, mimage.AxesImage) and not user_interpolation:
+            m.set_interpolation("none")
         if not isinstance(m, mimage.AxesImage):  # NOTE: PcolorImage is derivative
             self._fix_patch_edges(m, **edgefix_kw, **kw)
             self._add_auto_labels(m, **labels_kw)
@@ -7405,6 +7408,7 @@ def imshow(self, z, **kwargs):
         %(plot.imshow)s
         """
         kw = kwargs.copy()
+        kw.setdefault("interpolation", "none")
         center_levels = kw.pop("center_levels", None)
         kw = self._parse_cmap(
             z, center_levels=center_levels, default_discrete=False, **kw
@@ -7434,6 +7438,7 @@ def spy(self, z, **kwargs):
         %(plot.spy)s
         """
         kw = kwargs.copy()
+        user_interpolation = "interpolation" in kw
         kw.update(_pop_props(kw, "line"))  # takes valid Line2D properties
         default_cmap = pcolors.DiscreteColormap(["w", "k"], "_no_name")
         center_levels = kw.pop("center_levels", None)
@@ -7442,6 +7447,8 @@ def spy(self, z, **kwargs):
         )
         guide_kw = _pop_params(kw, self._update_guide)
         m = self._call_native("spy", z, **kw)
+        if isinstance(m, mimage.AxesImage) and not user_interpolation:
+            m.set_interpolation("none")
         self._update_guide(m, queue_colorbar=False, **guide_kw)
         return m
 

ultraplot/internals/rcsetup.py

@@ -906,7 +906,9 @@ def _validator_accepts(validator, value):
     "hatch.color": BLACK,
     "hatch.linewidth": LINEWIDTH,
     "image.cmap": CMAPSEQ,
-    "image.interpolation": "none",
+    # Keep matplotlib default globally to avoid affecting third-party raster artists.
+    # UltraPlot image methods apply their own interpolation defaults locally.
+    "image.interpolation": "auto",
     "lines.linestyle": "-",
     "lines.linewidth": 1.5,
     "lines.markersize": 6.0,

ultraplot/tests/test_config.py

@@ -274,3 +274,23 @@ def test_matplotlib_import_before_ultraplot_allows_custom_fontsize_tokens():
         "    uplt.rc[key] = 'med-large'\n"
     )
     assert result.returncode == 0, result.stderr
+
+
+def test_ultraplot_subplots_does_not_force_global_image_interpolation():
+    """
+    Regression test for issue #588: creating UltraPlot figures should not force
+    global raster interpolation defaults used by third-party OffsetImage artists.
+    """
+    result = _run_in_subprocess(
+        "import matplotlib as mpl\n"
+        "from matplotlib.offsetbox import OffsetImage\n"
+        "mpl.rcParams['image.interpolation'] = 'auto'\n"
+        "import ultraplot as uplt\n"
+        "fig, ax = uplt.subplots()\n"
+        "fig.canvas.draw()\n"
+        "uplt.close(fig)\n"
+        "assert mpl.rcParams['image.interpolation'] == 'auto'\n"
+        "img = OffsetImage([[[0, 0, 0, 0]]]).get_children()[0]\n"
+        "assert img.get_interpolation() == 'auto'\n"
+    )
+    assert result.returncode == 0, result.stderr

ultraplot/tests/test_imshow.py

@@ -103,3 +103,13 @@ def test_colorbar(rng):
     m = axs[2].imshow(data, cmap="oslo", colorbar="b")
     axs[2].format(title="Imshow plot\ndiscrete=False (default)", yformatter="auto")
     return fig
+
+
+def test_imshow_defaults_to_none_when_rc_interpolation_is_auto():
+    with plt.rc.context({"image.interpolation": "auto"}):
+        fig, ax = plt.subplots()
+        m_default = ax.imshow(np.arange(4).reshape(2, 2))
+        m_override = ax.imshow(np.arange(4).reshape(2, 2), interpolation="nearest")
+        assert m_default.get_interpolation() == "none"
+        assert m_override.get_interpolation() == "nearest"
+        plt.close(fig)