Start from zero index when reading GimpPaletteFile

Tests/test_file_gimppalette.py

@@ -32,3 +32,4 @@ def test_get_palette() -> None:
 
     # Assert
     assert mode == "RGB"
+    assert len(palette) / 3 == 8

src/PIL/GimpPaletteFile.py

@@ -18,22 +18,19 @@
 import re
 from typing import IO
 
-from ._binary import o8
-
 
 class GimpPaletteFile:
     """File handler for GIMP's palette format."""
 
     rawmode = "RGB"
 
     def __init__(self, fp: IO[bytes]) -> None:
-        palette = [o8(i) * 3 for i in range(256)]
-
         if not fp.readline().startswith(b"GIMP Palette"):
             msg = "not a GIMP palette file"
             raise SyntaxError(msg)
 
-        for i in range(256):
+        palette: list[int] = []
+        for _ in range(256):
             s = fp.readline()
             if not s:
                 break
@@ -45,14 +42,14 @@
                 msg = "bad palette file"
                 raise SyntaxError(msg)
 
-            v = tuple(map(int, s.split()[:3]))
-            if len(v) != 3:
+            v = s.split(maxsplit=3)
+            if len(v) < 3:
                 msg = "bad palette entry"
                 raise ValueError(msg)
 
-            palette[i] = o8(v[0]) + o8(v[1]) + o8(v[2])
+            palette += (int(v[i]) for i in range(3))
 
-        self.palette = b"".join(palette)
+        self.palette = bytes(palette)
 
     def getpalette(self) -> tuple[bytes, str]:
         return self.palette, self.rawmode