Simplified SPIDER code

src/PIL/SpiderImagePlugin.py

@@ -132,15 +132,15 @@ def _open(self) -> None:
         self.istack = int(h[24])
         self.imgnumber = int(h[27])
 
+        self.n_frames = 1
         if self.istack == 0 and self.imgnumber == 0:
             # stk=0, img=0: a regular 2D image
             offset = hdrlen
-            self._nimages = 1
         elif self.istack > 0 and self.imgnumber == 0:
             # stk>0, img=0: Opening the stack for the first time
             self.imgbytes = int(h[12]) * int(h[2]) * 4
             self.hdrlen = hdrlen
-            self._nimages = int(h[26])
+            self.n_frames = int(h[26])
             # Point to the first image in the stack
             offset = hdrlen * 2
             self.imgnumber = 1
@@ -151,6 +151,7 @@ def _open(self) -> None:
         else:
             msg = "inconsistent stack header values"
             raise SyntaxError(msg)
+        self.is_animated = self.n_frames > 1
 
         if self.bigendian:
             self.rawmode = "F;32BF"
@@ -161,14 +162,6 @@ def _open(self) -> None:
         self.tile = [ImageFile._Tile("raw", (0, 0) + self.size, offset, self.rawmode)]
         self._fp = self.fp  # FIXME: hack
 
-    @property
-    def n_frames(self) -> int:
-        return self._nimages
-
-    @property
-    def is_animated(self) -> bool:
-        return self._nimages > 1
-
     # 1st image index is zero (although SPIDER imgnumber starts at 1)
     def tell(self) -> int:
         if self.imgnumber < 1: