diff --git a/conftest.py b/conftest.py
index 57a5a80db..3000bdd4b 100644
--- a/conftest.py
+++ b/conftest.py
@@ -4,6 +4,7 @@ import sys
 
 from PIL import Image
 from PIL import PdfParser
+from PIL import SpiderImagePlugin
 
 pytest_plugins = ["Tests.helper"]
 
@@ -12,6 +13,8 @@ def calculate_coverage(test_name):
     all_branches = {
         "branches1": Image.branches,
         "branches2": PdfParser.XrefTable.branches,
+        "branches3": SpiderImagePlugin.branches1,
+        "branches4": SpiderImagePlugin.branches2,
         # Add more
     }
 
@@ -47,4 +50,3 @@ def pytest_sessionfinish(session, exitstatus):
     coverage = calculate_coverage(test_name)
     print("\nBRANCH COVERAGE for", test_name, ":", coverage, "%\n")
 
-    
\ No newline at end of file
diff --git a/src/PIL/SpiderImagePlugin.py b/src/PIL/SpiderImagePlugin.py
index 14aff84e0..e573345de 100644
--- a/src/PIL/SpiderImagePlugin.py
+++ b/src/PIL/SpiderImagePlugin.py
@@ -42,6 +42,33 @@ from typing import IO, TYPE_CHECKING
 from . import Image, ImageFile
 
 
+branches1 = {
+    "1": False,
+    "2": False,
+    "3": False,
+    "4": False,
+    "5": False,
+    "6": False,
+    "7": False,
+    "8": False,
+    "9": False,
+    "10": False,
+    "11": False,
+    "12": False,
+    "13": False,
+    "14": False,
+}
+
+branches2 = {
+    "1": False,
+    "2": False,
+    "3": False,
+    "4": False,
+    "5": False,
+    "6": False,
+    "7": False,
+}
+
 def isInt(f):
     try:
         i = int(f)
@@ -104,35 +131,52 @@ class SpiderImageFile(ImageFile.ImageFile):
         f = self.fp.read(n)
 
         try:
+            branches1["1"] = True
             self.bigendian = 1
             t = struct.unpack(">27f", f)  # try big-endian first
             hdrlen = isSpiderHeader(t)
+
             if hdrlen == 0:
+                branches1["2"] = True
                 self.bigendian = 0
                 t = struct.unpack("<27f", f)  # little-endian
                 hdrlen = isSpiderHeader(t)
+            else:  # ADDED FOR BRANCH MARKING
+                branches1["3"] = True
+
             if hdrlen == 0:
+                branches1["4"] = True
                 msg = "not a valid Spider file"
                 raise SyntaxError(msg)
+            else:  # ADDED FOR BRANCH MARKING
+                branches1["5"] = True
+
         except struct.error as e:
+            branches1["6"] = True
             msg = "not a valid Spider file"
             raise SyntaxError(msg) from e
 
         h = (99,) + t  # add 1 value : spider header index starts at 1
         iform = int(h[5])
+
         if iform != 1:
+            branches1["7"] = True
             msg = "not a Spider 2D image"
             raise SyntaxError(msg)
+        else:  # ADDED FOR BRANCH MARKING
+            branches1["8"] = True
 
         self._size = int(h[12]), int(h[2])  # size in pixels (width, height)
         self.istack = int(h[24])
         self.imgnumber = int(h[27])
 
         if self.istack == 0 and self.imgnumber == 0:
+            branches1["9"] = True
             # stk=0, img=0: a regular 2D image
             offset = hdrlen
             self._nimages = 1
         elif self.istack > 0 and self.imgnumber == 0:
+            branches1["10"] = True
             # stk>0, img=0: Opening the stack for the first time
             self.imgbytes = int(h[12]) * int(h[2]) * 4
             self.hdrlen = hdrlen
@@ -141,16 +185,20 @@ class SpiderImageFile(ImageFile.ImageFile):
             offset = hdrlen * 2
             self.imgnumber = 1
         elif self.istack == 0 and self.imgnumber > 0:
+            branches1["11"] = True
             # stk=0, img>0: an image within the stack
             offset = hdrlen + self.stkoffset
             self.istack = 2  # So Image knows it's still a stack
         else:
+            branches1["12"] = True
             msg = "inconsistent stack header values"
             raise SyntaxError(msg)
 
         if self.bigendian:
+            branches1["13"] = True
             self.rawmode = "F;32BF"
         else:
+            branches1["14"] = True
             self.rawmode = "F;32F"
         self._mode = "F"
 
@@ -174,10 +222,18 @@ class SpiderImageFile(ImageFile.ImageFile):
 
     def seek(self, frame: int) -> None:
         if self.istack == 0:
+            branches2["1"] = True
             msg = "attempt to seek in a non-stack file"
             raise EOFError(msg)
+        else:  # ADDED FOR BRANCH MARKING
+            branches2["2"] = True
+
         if not self._seek_check(frame):
+            branches2["3"] = True
             return
+        else:  # ADDED FOR BRANCH MARKING
+            branches2["4"] = True
+
         self.stkoffset = self.hdrlen + frame * (self.hdrlen + self.imgbytes)
         self.fp = self._fp
         self.fp.seek(self.stkoffset)