Replace ImageFile _seek_check() with SeekableImageFile seek()

Author: radarhere

Tests/test_file_spider.py

@@ -158,12 +158,18 @@ def test_invalid_file() -> None:
 
 def test_nonstack_file() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, SpiderImagePlugin.SpiderImageFile)
+        im.imgnumber = 2
+
         with pytest.raises(EOFError):
             im.seek(0)
 
 
 def test_nonstack_dos() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, SpiderImagePlugin.SpiderImageFile)
+        im.imgnumber = 2
+
         with pytest.raises(EOFError):
             im.seek(0)
 

docs/reference/ImageFile.rst

@@ -62,6 +62,10 @@ Classes
     :undoc-members:
     :show-inheritance:
 
+.. autoclass:: PIL.ImageFile.SeekableImageFile()
+    :members:
+    :show-inheritance:
+
 .. autoclass:: PIL.ImageFile.StubHandler()
     :members:
     :show-inheritance:

src/PIL/AvifImagePlugin.py

@@ -64,7 +64,7 @@ def _get_default_max_threads() -> int:
         return os.cpu_count() or 1
 
 
-class AvifImageFile(ImageFile.ImageFile):
+class AvifImageFile(ImageFile.SeekableImageFile):
     format = "AVIF"
     format_description = "AVIF image"
     __frame = -1
@@ -112,9 +112,7 @@ def _open(self) -> None:
             self.info["exif"] = exif
         self.seek(0)
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         self.info.pop("timestamp", None)
         self.info.pop("duration", None)
 

src/PIL/DcxImagePlugin.py

@@ -24,7 +24,7 @@
 
 __lazy_modules__ = {"PIL._binary", "PIL._util"}
 
-from . import Image
+from . import Image, ImageFile
 from ._binary import i32le as i32
 from ._util import DeferredError
 from .PcxImagePlugin import PcxImageFile
@@ -40,7 +40,7 @@ def _accept(prefix: bytes) -> bool:
 # Image plugin for the Intel DCX format.
 
 
-class DcxImageFile(PcxImageFile):
+class DcxImageFile(PcxImageFile, ImageFile.SeekableImageFile):
     format = "DCX"
     format_description = "Intel DCX"
     _close_exclusive_fp_after_loading = False
@@ -67,9 +67,7 @@ def _open(self) -> None:
         self.is_animated = self.n_frames > 1
         self.seek(0)
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         if isinstance(self._fp, DeferredError):
             raise self._fp.ex
         self.frame = frame

src/PIL/FliImagePlugin.py

@@ -42,7 +42,7 @@ def _accept(prefix: bytes) -> bool:
 # method to load individual frames.
 
 
-class FliImageFile(ImageFile.ImageFile):
+class FliImageFile(ImageFile.SeekableImageFile):
     format = "FLI"
     format_description = "Autodesk FLI/FLC Animation"
     _close_exclusive_fp_after_loading = False
@@ -135,9 +135,7 @@ def _palette(self, palette: list[tuple[int, int, int]], shift: int) -> None:
                 palette[i] = (r, g, b)
                 i += 1
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         if frame < self.__frame:
             self._seek(0)
 

src/PIL/GifImagePlugin.py

@@ -83,7 +83,7 @@ def _accept(prefix: bytes) -> bool:
 # GIF89 images.
 
 
-class GifImageFile(ImageFile.ImageFile):
+class GifImageFile(ImageFile.SeekableImageFile):
     format = "GIF"
     format_description = "Compuserve GIF"
     _close_exclusive_fp_after_loading = False
@@ -160,9 +160,7 @@ def is_animated(self) -> bool:
         self.seek(current)
         return is_animated
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         if frame < self.__frame:
             self._im = None
             self._seek(0)

src/PIL/ImImagePlugin.py

@@ -124,7 +124,7 @@ def number(s: Any) -> float:
 # Image plugin for the IFUNC IM file format.
 
 
-class ImImageFile(ImageFile.ImageFile):
+class ImImageFile(ImageFile.SeekableImageFile):
     format = "IM"
     format_description = "IFUNC Image Memory"
     _close_exclusive_fp_after_loading = False
@@ -293,9 +293,7 @@ def n_frames(self) -> int:
     def is_animated(self) -> bool:
         return self.info[FRAMES] > 1
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         if isinstance(self._fp, DeferredError):
             raise self._fp.ex
 

src/PIL/ImageFile.py

@@ -137,8 +137,6 @@ def __init__(
     ) -> None:
         super().__init__()
 
-        self._min_frame = 0
-
         self.custom_mimetype: str | None = None
 
         self.tile: list[_Tile] = []
@@ -482,7 +480,11 @@ def _get_fp_length(self, fp: IO[bytes] | None = None) -> int:
             fp = self.fp
         return _get_fp_length(fp)
 
-    def _seek_check(self, frame: int) -> bool:
+
+class SeekableImageFile(ImageFile):
+    _min_frame = 0
+
+    def seek(self, frame: int) -> None:
         if (
             frame < self._min_frame
             # Only check upper limit on frames if additional seek operations
@@ -495,7 +497,14 @@ def _seek_check(self, frame: int) -> bool:
             msg = "attempt to seek outside sequence"
             raise EOFError(msg)
 
-        return self.tell() != frame
+        if self.tell() == frame:
+            return
+
+        self._seekTo(frame)
+
+    @abc.abstractmethod
+    def _seekTo(self, frame: int) -> None:
+        pass
 
 
 class StubHandler(abc.ABC):

src/PIL/MicImagePlugin.py

@@ -71,9 +71,7 @@ def _open(self) -> None:
         self.__fp = self.fp
         self.seek(0)
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         filename = self.images[frame]
         self.fp = self.ole.openstream(filename)
 

src/PIL/MpoImagePlugin.py

@@ -105,7 +105,7 @@ def _save_all(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 # Image plugin for MPO images.
 
 
-class MpoImageFile(JpegImagePlugin.JpegImageFile):
+class MpoImageFile(JpegImagePlugin.JpegImageFile, ImageFile.SeekableImageFile):
     format = "MPO"
     format_description = "MPO (CIPA DC-007)"
     _close_exclusive_fp_after_loading = False
@@ -144,9 +144,7 @@ def load_seek(self, pos: int) -> None:
             raise self._fp.ex
         self._fp.seek(pos)
 
-    def seek(self, frame: int) -> None:
-        if not self._seek_check(frame):
-            return
+    def _seekTo(self, frame: int) -> None:
         if isinstance(self._fp, DeferredError):
             raise self._fp.ex
         self.fp = self._fp