Added _min_frame property

PIL/ImageFile.py

@@ -78,6 +78,8 @@ class ImageFile(Image.Image):
     def __init__(self, fp=None, filename=None):
         Image.Image.__init__(self)
 
+        self._min_frame = 0
+
         self.tile = None
         self.readonly = 1  # until we know better
 
@@ -276,11 +278,11 @@ class ImageFile(Image.Image):
     #     pass
 
     def _seek_check(self, frame):
-        if (frame < 0 or
+        if (frame < self._min_frame or
             # Only check upper limit on frames if additional seek operations
             # are not required to do so
             (not (hasattr(self, "_n_frames") and self._n_frames is None) and
-             frame >= self.n_frames)):
+             frame >= self.n_frames+self._min_frame)):
             raise EOFError("attempt to seek outside sequence")
 
         return self.tell() != frame

PIL/PsdImagePlugin.py

@@ -124,7 +124,8 @@ class PsdImageFile(ImageFile.ImageFile):
 
         # keep the file open
         self._fp = self.fp
-        self.frame = 0
+        self.frame = 1
+        self._min_frame = 1
 
     @property
     def n_frames(self):
@@ -140,8 +141,6 @@ class PsdImageFile(ImageFile.ImageFile):
 
         # seek to given layer (1..max)
         try:
-            if layer == 0:
-                raise IndexError
             name, mode, bbox, tile = self.layers[layer-1]
             self.mode = mode
             self.tile = tile

Tests/test_file_psd.py

@@ -34,26 +34,23 @@ class TestImagePsd(PillowTestCase):
 
     def test_eoferror(self):
         im = Image.open(test_file)
+        # PSD seek index starts at 1 rather than 0
+        n_frames = im.n_frames+1
 
-        n_frames = im.n_frames
-        while True:
-            n_frames -= 1
-            try:
-                # PSD seek index starts at 1 rather than 0
-                im.seek(n_frames+1)
-                break
-            except EOFError:
-                self.assertLess(im.tell(), n_frames)
+        # Test seeking past the last frame
+        self.assertRaises(EOFError, im.seek, n_frames)
+        self.assertLess(im.tell(), n_frames)
+
+        # Test that seeking to the last frame does not raise an error
+        im.seek(n_frames-1)
 
     def test_seek_tell(self):
         im = Image.open(test_file)
 
         layer_number = im.tell()
-        self.assertEqual(layer_number, 0)
+        self.assertEqual(layer_number, 1)
 
-        im.seek(0)
-        layer_number = im.tell()
-        self.assertEqual(layer_number, 0)
+        self.assertRaises(EOFError, im.seek, 0)
 
         im.seek(1)
         layer_number = im.tell()