Allow saving .ico files of 256x256 instead of 255x255

PIL/IcoImagePlugin.py

@@ -44,16 +44,17 @@ def _save(im, fp, filename):
     fp.write(_MAGIC)  # (2+2)
     sizes = im.encoderinfo.get("sizes",
                                [(16, 16), (24, 24), (32, 32), (48, 48),
-                                (64, 64), (128, 128), (255, 255)])
+                                (64, 64), (128, 128), (256, 256)])
     width, height = im.size
     filter(lambda x: False if (x[0] > width or x[1] > height or
-                               x[0] > 255 or x[1] > 255) else True, sizes)
+                               x[0] > 256 or x[1] > 256) else True, sizes)
     fp.write(struct.pack("<H", len(sizes)))  # idCount(2)
     offset = fp.tell() + len(sizes)*16
     for size in sizes:
         width, height = size
-        fp.write(struct.pack("B", width))  # bWidth(1)
-        fp.write(struct.pack("B", height))  # bHeight(1)
+        # 0 means 256
+        fp.write(struct.pack("B", width if width < 256 else 0))  # bWidth(1)
+        fp.write(struct.pack("B", height if height < 256 else 0))  # bHeight(1)
         fp.write(b"\0")  # bColorCount(1)
         fp.write(b"\0")  # bReserved(1)
         fp.write(b"\0\0")  # wPlanes(2)
@@ -215,13 +216,13 @@ def frame(self, idx):
                 total_bytes = int((w * im.size[1]) / 8)
 
                 self.buf.seek(and_mask_offset)
-                maskData = self.buf.read(total_bytes)
+                mask_data = self.buf.read(total_bytes)
 
                 # convert raw data to image
                 mask = Image.frombuffer(
                     '1',            # 1 bpp
                     im.size,        # (w, h)
-                    maskData,       # source chars
+                    mask_data,      # source chars
                     'raw',          # raw decoder
                     ('1;I', int(w/8), -1)  # 1bpp inverted, padded, reversed
                 )
@@ -278,6 +279,7 @@ def load_seek(self):
 #
 # --------------------------------------------------------------------
 
+
 Image.register_open(IcoImageFile.format, IcoImageFile, _accept)
 Image.register_save(IcoImageFile.format, _save)
 Image.register_extension(IcoImageFile.format, ".ico")

Tests/test_file_ico.py

@@ -48,6 +48,19 @@ def test_save_to_bytes(self):
         self.assert_image_equal(reloaded,
                                 hopper().resize((32, 32), Image.LANCZOS))
 
+    def test_save_256x256(self):
+        """Issue #2264 https://github.com/python-pillow/Pillow/issues/2264"""
+        # Arrange
+        im = Image.open("Tests/images/hopper_256x256.ico")
+        outfile = self.tempfile("temp_saved_hopper_256x256.ico")
+
+        # Act
+        im.save(outfile)
+        im_saved = Image.open(outfile)
+
+        # Assert
+        self.assertEqual(im_saved.size, (256, 256))
+
 
 if __name__ == '__main__':
     unittest.main()