Use _ensure_mutable() (#9200)

src/PIL/Image.py

@@ -2070,9 +2070,7 @@ class Image:
         :param value: The pixel value.
         """
 
-        if self.readonly:
-            self._copy()
-        self.load()
+        self._ensure_mutable()
 
         if (
             self.mode in ("P", "PA")

src/PIL/ImageDraw.py

@@ -76,9 +76,7 @@ class ImageDraw:
            must be the same as the image mode.  If omitted, the mode
            defaults to the mode of the image.
         """
-        im.load()
-        if im.readonly:
-            im._copy()  # make it writeable
+        im._ensure_mutable()
         blend = 0
         if mode is None:
             mode = im.mode