diff --git a/Tests/test_file_spider.py b/Tests/test_file_spider.py
index 9b82a962a..66c88e9d8 100644
--- a/Tests/test_file_spider.py
+++ b/Tests/test_file_spider.py
@@ -105,6 +105,7 @@ def test_load_image_series() -> None:
     img_list = SpiderImagePlugin.loadImageSeries(file_list)
 
     # Assert
+    assert img_list is not None
     assert len(img_list) == 1
     assert isinstance(img_list[0], Image.Image)
     assert img_list[0].size == (128, 128)
diff --git a/Tests/test_imagefile.py b/Tests/test_imagefile.py
index a269b846a..68b28ef07 100644
--- a/Tests/test_imagefile.py
+++ b/Tests/test_imagefile.py
@@ -209,7 +209,7 @@ class MockPyDecoder(ImageFile.PyDecoder):
 
         super().__init__(mode, *args)
 
-    def decode(self, buffer):
+    def decode(self, buffer: bytes) -> tuple[int, int]:
         # eof
         return -1, 0
 
@@ -222,7 +222,7 @@ class MockPyEncoder(ImageFile.PyEncoder):
 
         super().__init__(mode, *args)
 
-    def encode(self, buffer):
+    def encode(self, bufsize: int) -> tuple[int, int, bytes]:
         return 1, 1, b""
 
     def cleanup(self) -> None:
diff --git a/Tests/test_imageops_usm.py b/Tests/test_imageops_usm.py
index dbdd5b317..c8e2c0467 100644
--- a/Tests/test_imageops_usm.py
+++ b/Tests/test_imageops_usm.py
@@ -101,7 +101,7 @@ def test_blur_accuracy(test_images: dict[str, ImageFile.ImageFile]) -> None:
         assert i.im.getpixel((x, y))[c] >= 250
     # Fuzzy match.
 
-    def gp(x, y):
+    def gp(x: int, y: int) -> tuple[int, ...]:
         return i.im.getpixel((x, y))
 
     assert 236 <= gp(7, 4)[0] <= 239
diff --git a/Tests/test_imagepalette.py b/Tests/test_imagepalette.py
index 17f68710a..6cf0079dd 100644
--- a/Tests/test_imagepalette.py
+++ b/Tests/test_imagepalette.py
@@ -88,13 +88,13 @@ def test_file(tmp_path: Path) -> None:
 
     palette.save(f)
 
-    p = ImagePalette.load(f)
+    lut = ImagePalette.load(f)
 
     # load returns raw palette information
-    assert len(p[0]) == 768
-    assert p[1] == "RGB"
+    assert len(lut[0]) == 768
+    assert lut[1] == "RGB"
 
-    p = ImagePalette.raw(p[1], p[0])
+    p = ImagePalette.raw(lut[1], lut[0])
     assert isinstance(p, ImagePalette.ImagePalette)
     assert p.palette == palette.tobytes()
 
diff --git a/src/PIL/BlpImagePlugin.py b/src/PIL/BlpImagePlugin.py
index 59246c6e2..b9cefafdd 100644
--- a/src/PIL/BlpImagePlugin.py
+++ b/src/PIL/BlpImagePlugin.py
@@ -430,6 +430,7 @@ class BLPEncoder(ImageFile.PyEncoder):
 
     def _write_palette(self) -> bytes:
         data = b""
+        assert self.im is not None
         palette = self.im.getpalette("RGBA", "RGBA")
         for i in range(len(palette) // 4):
             r, g, b, a = palette[i * 4 : (i + 1) * 4]
@@ -444,6 +445,7 @@ class BLPEncoder(ImageFile.PyEncoder):
         offset = 20 + 16 * 4 * 2 + len(palette_data)
         data = struct.pack("<16I", offset, *((0,) * 15))
 
+        assert self.im is not None
         w, h = self.im.size
         data += struct.pack("<16I", w * h, *((0,) * 15))
 
diff --git a/src/PIL/ImageDraw2.py b/src/PIL/ImageDraw2.py
index 600e140e1..e89a78be4 100644
--- a/src/PIL/ImageDraw2.py
+++ b/src/PIL/ImageDraw2.py
@@ -24,7 +24,10 @@
 """
 from __future__ import annotations
 
+from typing import BinaryIO
+
 from . import Image, ImageColor, ImageDraw, ImageFont, ImagePath
+from ._typing import StrOrBytesPath
 
 
 class Pen:
@@ -45,7 +48,9 @@ class Brush:
 class Font:
     """Stores a TrueType font and color"""
 
-    def __init__(self, color, file, size=12):
+    def __init__(
+        self, color: str, file: StrOrBytesPath | BinaryIO, size: float = 12
+    ) -> None:
         # FIXME: add support for bitmap fonts
         self.color = ImageColor.getrgb(color)
         self.font = ImageFont.truetype(file, size)
diff --git a/src/PIL/ImageFile.py b/src/PIL/ImageFile.py
index 5d67409ea..69e7ee548 100644
--- a/src/PIL/ImageFile.py
+++ b/src/PIL/ImageFile.py
@@ -65,7 +65,7 @@ Dict of known error codes returned from :meth:`.PyDecoder.decode`,
 # Helpers
 
 
-def _get_oserror(error, *, encoder):
+def _get_oserror(error: int, *, encoder: bool) -> OSError:
     try:
         msg = Image.core.getcodecstatus(error)
     except AttributeError:
@@ -76,7 +76,7 @@ def _get_oserror(error, *, encoder):
     return OSError(msg)
 
 
-def raise_oserror(error):
+def raise_oserror(error: int) -> OSError:
     deprecate(
         "raise_oserror",
         12,
@@ -154,11 +154,12 @@ class ImageFile(Image.Image):
                 self.fp.close()
             raise
 
-    def get_format_mimetype(self):
+    def get_format_mimetype(self) -> str | None:
         if self.custom_mimetype:
             return self.custom_mimetype
         if self.format is not None:
             return Image.MIME.get(self.format.upper())
+        return None
 
     def __setstate__(self, state):
         self.tile = []
@@ -365,7 +366,7 @@ class StubImageFile(ImageFile):
     certain format, but relies on external code to load the file.
     """
 
-    def _open(self):
+    def _open(self) -> None:
         msg = "StubImageFile subclass must implement _open"
         raise NotImplementedError(msg)
 
@@ -381,7 +382,7 @@ class StubImageFile(ImageFile):
         self.__dict__ = image.__dict__
         return image.load()
 
-    def _load(self):
+    def _load(self) -> StubHandler | None:
         """(Hook) Find actual image loader."""
         msg = "StubImageFile subclass must implement _load"
         raise NotImplementedError(msg)
@@ -621,7 +622,7 @@ class PyCodecState:
         self.xoff = 0
         self.yoff = 0
 
-    def extents(self):
+    def extents(self) -> tuple[int, int, int, int]:
         return self.xoff, self.yoff, self.xoff + self.xsize, self.yoff + self.ysize
 
 
@@ -661,7 +662,7 @@ class PyCodec:
         """
         self.fd = fd
 
-    def setimage(self, im, extents=None):
+    def setimage(self, im, extents: tuple[int, int, int, int] | None = None) -> None:
         """
         Called from ImageFile to set the core output image for the codec
 
@@ -710,10 +711,10 @@ class PyDecoder(PyCodec):
     _pulls_fd = False
 
     @property
-    def pulls_fd(self):
+    def pulls_fd(self) -> bool:
         return self._pulls_fd
 
-    def decode(self, buffer):
+    def decode(self, buffer: bytes) -> tuple[int, int]:
         """
         Override to perform the decoding process.
 
@@ -738,6 +739,7 @@ class PyDecoder(PyCodec):
         if not rawmode:
             rawmode = self.mode
         d = Image._getdecoder(self.mode, "raw", rawmode)
+        assert self.im is not None
         d.setimage(self.im, self.state.extents())
         s = d.decode(data)
 
@@ -760,7 +762,7 @@ class PyEncoder(PyCodec):
     _pushes_fd = False
 
     @property
-    def pushes_fd(self):
+    def pushes_fd(self) -> bool:
         return self._pushes_fd
 
     def encode(self, bufsize: int) -> tuple[int, int, bytes]:
@@ -775,7 +777,7 @@ class PyEncoder(PyCodec):
         msg = "unavailable in base encoder"
         raise NotImplementedError(msg)
 
-    def encode_to_pyfd(self):
+    def encode_to_pyfd(self) -> tuple[int, int]:
         """
         If ``pushes_fd`` is ``True``, then this method will be used,
         and ``encode()`` will only be called once.
@@ -787,6 +789,7 @@ class PyEncoder(PyCodec):
             return 0, -8  # bad configuration
         bytes_consumed, errcode, data = self.encode(0)
         if data:
+            assert self.fd is not None
             self.fd.write(data)
         return bytes_consumed, errcode
 
diff --git a/src/PIL/ImagePalette.py b/src/PIL/ImagePalette.py
index 6473c4577..ed38285dc 100644
--- a/src/PIL/ImagePalette.py
+++ b/src/PIL/ImagePalette.py
@@ -38,23 +38,27 @@ class ImagePalette:
         Defaults to an empty palette.
     """
 
-    def __init__(self, mode: str = "RGB", palette: Sequence[int] | None = None) -> None:
+    def __init__(
+        self,
+        mode: str = "RGB",
+        palette: Sequence[int] | bytes | bytearray | None = None,
+    ) -> None:
         self.mode = mode
-        self.rawmode = None  # if set, palette contains raw data
+        self.rawmode: str | None = None  # if set, palette contains raw data
         self.palette = palette or bytearray()
         self.dirty: int | None = None
 
     @property
-    def palette(self):
+    def palette(self) -> Sequence[int] | bytes | bytearray:
         return self._palette
 
     @palette.setter
-    def palette(self, palette):
-        self._colors = None
+    def palette(self, palette: Sequence[int] | bytes | bytearray) -> None:
+        self._colors: dict[tuple[int, ...], int] | None = None
         self._palette = palette
 
     @property
-    def colors(self) -> dict[tuple[int, int, int] | tuple[int, int, int, int], int]:
+    def colors(self) -> dict[tuple[int, ...], int]:
         if self._colors is None:
             mode_len = len(self.mode)
             self._colors = {}
@@ -66,9 +70,7 @@ class ImagePalette:
         return self._colors
 
     @colors.setter
-    def colors(
-        self, colors: dict[tuple[int, int, int] | tuple[int, int, int, int], int]
-    ) -> None:
+    def colors(self, colors: dict[tuple[int, ...], int]) -> None:
         self._colors = colors
 
     def copy(self) -> ImagePalette:
@@ -82,7 +84,7 @@ class ImagePalette:
 
         return new
 
-    def getdata(self) -> tuple[str, bytes]:
+    def getdata(self) -> tuple[str, Sequence[int] | bytes | bytearray]:
         """
         Get palette contents in format suitable for the low-level
         ``im.putpalette`` primitive.
@@ -137,7 +139,7 @@ class ImagePalette:
 
     def getcolor(
         self,
-        color: tuple[int, int, int] | tuple[int, int, int, int],
+        color: tuple[int, ...],
         image: Image.Image | None = None,
     ) -> int:
         """Given an rgb tuple, allocate palette entry.
@@ -162,12 +164,13 @@ class ImagePalette:
             except KeyError as e:
                 # allocate new color slot
                 index = self._new_color_index(image, e)
+                assert isinstance(self._palette, bytearray)
                 self.colors[color] = index
                 if index * 3 < len(self.palette):
                     self._palette = (
-                        self.palette[: index * 3]
+                        self._palette[: index * 3]
                         + bytes(color)
-                        + self.palette[index * 3 + 3 :]
+                        + self._palette[index * 3 + 3 :]
                     )
                 else:
                     self._palette += bytes(color)
@@ -204,7 +207,7 @@ class ImagePalette:
 # Internal
 
 
-def raw(rawmode, data) -> ImagePalette:
+def raw(rawmode, data: Sequence[int] | bytes | bytearray) -> ImagePalette:
     palette = ImagePalette()
     palette.rawmode = rawmode
     palette.palette = data
@@ -216,9 +219,9 @@ def raw(rawmode, data) -> ImagePalette:
 # Factories
 
 
-def make_linear_lut(black, white):
+def make_linear_lut(black: int, white: float) -> list[int]:
     if black == 0:
-        return [white * i // 255 for i in range(256)]
+        return [int(white * i // 255) for i in range(256)]
 
     msg = "unavailable when black is non-zero"
     raise NotImplementedError(msg)  # FIXME
@@ -251,15 +254,22 @@ def wedge(mode: str = "RGB") -> ImagePalette:
     return ImagePalette(mode, [i // len(mode) for i in palette])
 
 
-def load(filename):
+def load(filename: str) -> tuple[bytes, str]:
     # FIXME: supports GIMP gradients only
 
     with open(filename, "rb") as fp:
-        for paletteHandler in [
+        paletteHandlers: list[
+            type[
+                GimpPaletteFile.GimpPaletteFile
+                | GimpGradientFile.GimpGradientFile
+                | PaletteFile.PaletteFile
+            ]
+        ] = [
             GimpPaletteFile.GimpPaletteFile,
             GimpGradientFile.GimpGradientFile,
             PaletteFile.PaletteFile,
-        ]:
+        ]
+        for paletteHandler in paletteHandlers:
             try:
                 fp.seek(0)
                 lut = paletteHandler(fp).getpalette()
diff --git a/src/PIL/ImageWin.py b/src/PIL/ImageWin.py
index 6c29e2590..978c5a9d1 100644
--- a/src/PIL/ImageWin.py
+++ b/src/PIL/ImageWin.py
@@ -69,19 +69,22 @@ class Dib:
                  defines the size of the image.
     """
 
-    def __init__(self, image, size=None):
-        if hasattr(image, "mode") and hasattr(image, "size"):
+    def __init__(
+        self, image: Image.Image | str, size: tuple[int, int] | list[int] | None = None
+    ) -> None:
+        if isinstance(image, str):
+            mode = image
+            image = ""
+        else:
             mode = image.mode
             size = image.size
-        else:
-            mode = image
-            image = None
         if mode not in ["1", "L", "P", "RGB"]:
             mode = Image.getmodebase(mode)
         self.image = Image.core.display(mode, size)
         self.mode = mode
         self.size = size
         if image:
+            assert not isinstance(image, str)
             self.paste(image)
 
     def expose(self, handle):
diff --git a/src/PIL/SpiderImagePlugin.py b/src/PIL/SpiderImagePlugin.py
index a6cc00019..f5a09c3ef 100644
--- a/src/PIL/SpiderImagePlugin.py
+++ b/src/PIL/SpiderImagePlugin.py
@@ -37,12 +37,12 @@ from __future__ import annotations
 import os
 import struct
 import sys
-from typing import IO, TYPE_CHECKING
+from typing import IO, TYPE_CHECKING, Any, Tuple, cast
 
 from . import Image, ImageFile
 
 
-def isInt(f):
+def isInt(f: Any) -> int:
     try:
         i = int(f)
         if f - i == 0:
@@ -62,7 +62,7 @@ iforms = [1, 3, -11, -12, -21, -22]
 # otherwise returns 0
 
 
-def isSpiderHeader(t):
+def isSpiderHeader(t: tuple[float, ...]) -> int:
     h = (99,) + t  # add 1 value so can use spider header index start=1
     # header values 1,2,5,12,13,22,23 should be integers
     for i in [1, 2, 5, 12, 13, 22, 23]:
@@ -82,7 +82,7 @@ def isSpiderHeader(t):
     return labbyt
 
 
-def isSpiderImage(filename):
+def isSpiderImage(filename: str) -> int:
     with open(filename, "rb") as fp:
         f = fp.read(92)  # read 23 * 4 bytes
     t = struct.unpack(">23f", f)  # try big-endian first
@@ -184,13 +184,15 @@ class SpiderImageFile(ImageFile.ImageFile):
         self._open()
 
     # returns a byte image after rescaling to 0..255
-    def convert2byte(self, depth=255):
-        (minimum, maximum) = self.getextrema()
-        m = 1
+    def convert2byte(self, depth: int = 255) -> Image.Image:
+        extrema = self.getextrema()
+        assert isinstance(extrema[0], float)
+        minimum, maximum = cast(Tuple[float, float], extrema)
+        m: float = 1
         if maximum != minimum:
             m = depth / (maximum - minimum)
         b = -m * minimum
-        return self.point(lambda i, m=m, b=b: i * m + b).convert("L")
+        return self.point(lambda i: i * m + b).convert("L")
 
     if TYPE_CHECKING:
         from . import ImageTk
@@ -207,10 +209,10 @@ class SpiderImageFile(ImageFile.ImageFile):
 
 
 # given a list of filenames, return a list of images
-def loadImageSeries(filelist=None):
+def loadImageSeries(filelist: list[str] | None = None) -> list[SpiderImageFile] | None:
     """create a list of :py:class:`~PIL.Image.Image` objects for use in a montage"""
     if filelist is None or len(filelist) < 1:
-        return
+        return None
 
     imglist = []
     for img in filelist: