Correct IFDRational.__float__() return value

Tests/test_tiff_ifdrational.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import math
 from fractions import Fraction
 from pathlib import Path
 
@@ -38,6 +39,18 @@ def test_sanity() -> None:
     _test_equal(7, 5, 1.4)
 
 
+def test_float() -> None:
+    # float() must agree with ==, int() and repr(), which all use the
+    # normalized fraction
+    r = IFDRational(1.5, 3)
+    assert r == 0.5
+    assert float(r) == 0.5
+
+    # Integer numerator and 0/0 (nan) cases
+    assert float(IFDRational(4, 2)) == 2.0
+    assert math.isnan(float(IFDRational(0, 0)))
+
+
 def test_ranges() -> None:
     for num in range(1, 10):
         for denom in range(1, 10):

src/PIL/TiffImagePlugin.py

@@ -464,6 +464,7 @@ def __setstate__(self, state: list[float | Fraction | IntegralLike]) -> None:
     __ceil__ = _delegate("__ceil__")
     __floor__ = _delegate("__floor__")
     __round__ = _delegate("__round__")
+    __float__ = _delegate("__float__")
     # Python >= 3.11
     if hasattr(Fraction, "__int__"):
         __int__ = _delegate("__int__")