Merge pull request matplotlib#24816 from chahak13/transparent_inset_axes

[FIX]: Make inset axes transparent on savefig(..., transparent=True)

Author: ksunden

lib/matplotlib/figure.py

@@ -3316,12 +3316,37 @@ def savefig(self, fname, *, transparent=None, **kwargs):
 
         with ExitStack() as stack:
             if transparent:
+                def _recursively_make_subfig_transparent(exit_stack, subfig):
+                    exit_stack.enter_context(
+                        subfig.patch._cm_set(
+                            facecolor="none", edgecolor="none"))
+                    for ax in subfig.axes:
+                        exit_stack.enter_context(
+                            ax.patch._cm_set(
+                                facecolor="none", edgecolor="none"))
+                    for sub_subfig in subfig.subfigs:
+                        _recursively_make_subfig_transparent(
+                            exit_stack, sub_subfig)
+
+                def _recursively_make_axes_transparent(exit_stack, ax):
+                    exit_stack.enter_context(
+                        ax.patch._cm_set(facecolor="none", edgecolor="none"))
+                    for child_ax in ax.child_axes:
+                        exit_stack.enter_context(
+                            child_ax.patch._cm_set(
+                                facecolor="none", edgecolor="none"))
+                    for child_childax in ax.child_axes:
+                        _recursively_make_axes_transparent(
+                            exit_stack, child_childax)
+
                 kwargs.setdefault('facecolor', 'none')
                 kwargs.setdefault('edgecolor', 'none')
+                # set subfigure to appear transparent in printed image
+                for subfig in self.subfigs:
+                    _recursively_make_subfig_transparent(stack, subfig)
+                # set axes to be transparent
                 for ax in self.axes:
-                    stack.enter_context(
-                        ax.patch._cm_set(facecolor='none', edgecolor='none'))
-
+                    _recursively_make_axes_transparent(stack, ax)
             self.canvas.print_figure(fname, **kwargs)
 
     def ginput(self, n=1, timeout=30, show_clicks=True,

lib/matplotlib/tests/test_figure.py

@@ -539,6 +539,29 @@ def test_savefig_preserve_layout_engine(tmp_path):
     assert fig.get_layout_engine()._compress
 
 
+@mpl.rc_context({"savefig.transparent": True})
+@check_figures_equal(extensions=["png"])
+def test_savefig_transparent(fig_test, fig_ref):
+    # create two transparent subfigures with corresponding transparent inset
+    # axes. the entire background of the image should be transparent.
+    gs1 = fig_test.add_gridspec(3, 3, left=0.05, wspace=0.05)
+    f1 = fig_test.add_subfigure(gs1[:, :])
+    f2 = f1.add_subfigure(gs1[0, 0])
+
+    ax12 = f2.add_subplot(gs1[:, :])
+
+    ax1 = f1.add_subplot(gs1[:-1, :])
+    iax1 = ax1.inset_axes([.1, .2, .3, .4])
+    iax2 = iax1.inset_axes([.1, .2, .3, .4])
+
+    ax2 = fig_test.add_subplot(gs1[-1, :-1])
+    ax3 = fig_test.add_subplot(gs1[-1, -1])
+
+    for ax in [ax12, ax1, iax1, iax2, ax2, ax3]:
+        ax.set(xticks=[], yticks=[])
+        ax.spines[:].set_visible(False)
+
+
 def test_figure_repr():
     fig = plt.figure(figsize=(10, 20), dpi=10)
     assert repr(fig) == "<Figure size 100x200 with 0 Axes>"