Simplify overflow handling of seed tolerance in flood_fill

skimage/_shared/dtype.py

@@ -71,3 +71,42 @@ def numeric_dtype_min_max(dtype):
     else:
         raise ValueError(f"unsupported dtype {dtype!r}")
     return min_, max_
+
+
+def to_py_scalar(x):
+    """Convert a NumPy scalar to the corresponding Python scalar.
+
+    Casts the given scalar to int, float, complex or bool depending on the
+    scalar dtype.
+
+    Parameters
+    ----------
+    x : NumPy scalar
+        The scalar to convert.
+
+    Returns
+    -------
+    y : Python scalar
+        The corresponding Python scalar.
+
+    Examples
+    --------
+    >>> type(to_py_scalar(np.bool(True)))
+    <class 'bool'>
+    >>> type(to_py_scalar(np.uint8(3)))
+    <class 'int'>
+    >>> type(to_py_scalar(np.float64(3)))
+    <class 'float'>
+    >>> type(to_py_scalar(np.complex64(3j)))
+    <class 'complex'>
+    """
+    if np.issubdtype(x, np.integer):
+        return int(x)
+    elif np.issubdtype(x, np.floating):
+        return float(x)
+    elif np.issubdtype(x, np.complexfloating):
+        return complex(x)
+    elif np.issubdtype(x, np.dtype(bool)):
+        return bool(x)
+    else:
+        raise ValueError(f"unsupported scalar type {type(x)}")

skimage/morphology/_flood_fill.py

@@ -13,7 +13,7 @@
     _resolve_neighborhood,
     _set_border_values,
 )
-from .._shared.dtype import numeric_dtype_min_max
+from .._shared.dtype import numeric_dtype_min_max, to_py_scalar
 
 
 def flood_fill(
@@ -276,15 +276,8 @@ def flood(image, seed_point, *, footprint=None, connectivity=None, tolerance=Non
             # Account for over- & underflow problems with seed_value ± tolerance
             # in a way that works with NumPy 1 & 2
             min_value, max_value = numeric_dtype_min_max(seed_value.dtype)
-            with np.errstate(over="raise", under="raise"):
-                try:
-                    low_tol = max(min_value, seed_value - tolerance)
-                except (OverflowError, FloatingPointError):
-                    low_tol = min_value
-                try:
-                    high_tol = min(max_value, seed_value + tolerance)
-                except (OverflowError, FloatingPointError):
-                    high_tol = max_value
+            low_tol = max(min_value, to_py_scalar(seed_value) - tolerance)
+            high_tol = min(max_value, to_py_scalar(seed_value) + tolerance)
 
             _flood_fill_tolerance(
                 working_image.ravel(order),