Do not load ICO if already loaded

Tests/test_file_ico.py

@@ -1,7 +1,7 @@
 from .helper import PillowTestCase, hopper
 
 import io
-from PIL import Image, IcoImagePlugin
+from PIL import Image, ImageDraw, IcoImagePlugin
 
 TEST_ICO_FILE = "Tests/images/hopper.ico"
 
@@ -90,3 +90,16 @@ class TestFileIco(PillowTestCase):
         im = self.assert_warning(UserWarning,
                                  Image.open, "Tests/images/hopper_unexpected.ico")
         self.assertEqual(im.size, (16, 16))
+
+    def test_draw_reloaded(self):
+        im = Image.open(TEST_ICO_FILE)
+        outfile = self.tempfile("temp_saved_hopper_draw.ico")
+
+        draw = ImageDraw.Draw(im)
+        draw.line((0, 0) + im.size, '#f00')
+        im.save(outfile)
+
+        im = Image.open(outfile)
+        im.save("Tests/images/hopper_draw.ico")
+        reloaded = Image.open("Tests/images/hopper_draw.ico")
+        self.assert_image_equal(im, reloaded)

src/PIL/IcoImagePlugin.py

@@ -288,6 +288,9 @@ class IcoImageFile(ImageFile.ImageFile):
         self._size = value
 
     def load(self):
+        if self.im and self.im.size == self.size:
+            # Already loaded
+            return
         im = self.ico.getimage(self.size)
         # if tile is PNG, it won't really be loaded yet
         im.load()