diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index b7bb514acc5..ec1cff89636 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -710,7 +710,7 @@ def __setstate__(self, state):
             self.putpalette(palette)
         self.frombytes(data)
 
-    def tobytes(self, encoder_name="raw", *args):
+    def tobytes(self, encoder_name: str = "raw", *args) -> bytes:
         """
         Return image as a bytes object.
 
@@ -788,7 +788,7 @@ def tobitmap(self, name="image"):
             ]
         )
 
-    def frombytes(self, data, decoder_name="raw", *args):
+    def frombytes(self, data: bytes, decoder_name: str = "raw", *args) -> None:
         """
         Loads this image with pixel data from a bytes object.
 
@@ -1297,7 +1297,7 @@ def filter(self, filter):
         ]
         return merge(self.mode, ims)
 
-    def getbands(self):
+    def getbands(self) -> tuple[str, ...]:
         """
         Returns a tuple containing the name of each band in this image.
         For example, ``getbands`` on an RGB image returns ("R", "G", "B").
@@ -2495,7 +2495,7 @@ def show(self, title=None):
 
         _show(self, title=title)
 
-    def split(self):
+    def split(self) -> tuple[Image, ...]:
         """
         Split this image into individual bands. This method returns a
         tuple of individual image bands from an image. For example,
diff --git a/src/PIL/SgiImagePlugin.py b/src/PIL/SgiImagePlugin.py
index f9a10f6109c..ccf661ff1f3 100644
--- a/src/PIL/SgiImagePlugin.py
+++ b/src/PIL/SgiImagePlugin.py
@@ -24,13 +24,14 @@
 
 import os
 import struct
+from io import BytesIO
 
 from . import Image, ImageFile
 from ._binary import i16be as i16
 from ._binary import o8
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return len(prefix) >= 2 and i16(prefix) == 474
 
 
@@ -52,8 +53,10 @@ class SgiImageFile(ImageFile.ImageFile):
     format = "SGI"
     format_description = "SGI Image File Format"
 
-    def _open(self):
+    def _open(self) -> None:
         # HEAD
+        assert self.fp is not None
+
         headlen = 512
         s = self.fp.read(headlen)
 
@@ -122,7 +125,7 @@ def _open(self):
             ]
 
 
-def _save(im, fp, filename):
+def _save(im: Image.Image, fp: BytesIO, filename: str) -> None:
     if im.mode not in {"RGB", "RGBA", "L"}:
         msg = "Unsupported SGI image mode"
         raise ValueError(msg)
@@ -168,8 +171,8 @@ def _save(im, fp, filename):
     # Maximum Byte value (255 = 8bits per pixel)
     pinmax = 255
     # Image name (79 characters max, truncated below in write)
-    img_name = os.path.splitext(os.path.basename(filename))[0]
-    img_name = img_name.encode("ascii", "ignore")
+    filename = os.path.basename(filename)
+    img_name = os.path.splitext(filename)[0].encode("ascii", "ignore")
     # Standard representation of pixel in the file
     colormap = 0
     fp.write(struct.pack(">h", magic_number))
@@ -201,7 +204,10 @@ def _save(im, fp, filename):
 class SGI16Decoder(ImageFile.PyDecoder):
     _pulls_fd = True
 
-    def decode(self, buffer):
+    def decode(self, buffer: bytes) -> tuple[int, int]:
+        assert self.fd is not None
+        assert self.im is not None
+
         rawmode, stride, orientation = self.args
         pagesize = self.state.xsize * self.state.ysize
         zsize = len(self.mode)