Save a couple of numpy conversions.

anntzer · anntzer · commit 03ecd78faebb · 2020-05-24T00:49:28.000+02:00
diff --git a/lib/matplotlib/backends/backend_agg.py b/lib/matplotlib/backends/backend_agg.py
@@ -500,9 +500,8 @@ def print_png(self, filename_or_obj, *args,
         """
         FigureCanvasAgg.draw(self)
         mpl.image.imsave(
-            filename_or_obj, np.asarray(self.buffer_rgba()), format="png",
-            origin="upper", dpi=self.figure.dpi,
-            metadata=metadata, pil_kwargs=pil_kwargs)
+            filename_or_obj, self.buffer_rgba(), format="png", origin="upper",
+            dpi=self.figure.dpi, metadata=metadata, pil_kwargs=pil_kwargs)
 
     def print_to_buffer(self):
         FigureCanvasAgg.draw(self)
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -1514,7 +1514,15 @@ def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
             origin = mpl.rcParams["image.origin"]
         if origin == "lower":
             arr = arr[::-1]
-        rgba = sm.to_rgba(arr, bytes=True)
+        if (isinstance(arr, memoryview) and arr.format == "B"
+                and arr.ndim == 3 and arr.shape[-1] == 4):
+            # Such an ``arr`` would also be handled fine by sm.to_rgba (after
+            # casting with asarray), but it is useful to special-case it
+            # because that's what backend_agg passes, and can be in fact used
+            # as is, saving a few operations.
+            rgba = arr
+        else:
+            rgba = sm.to_rgba(arr, bytes=True)
         if pil_kwargs is None:
             pil_kwargs = {}
         pil_shape = (rgba.shape[1], rgba.shape[0])
