Structure tensor wrapper

In addition to the wrapper and viz function, I also black formatted some of the my previous merges as I had forgot it. Also increased the width of the local thickness slice index slider to be coherent with the ones in the structure tensor viz function

qim3d/processing/structure_tensor.py

+"""Wrapper for the structure tensor function from the structure_tensor package"""
+import numpy as np
+import structure_tensor as st
+from typing import Tuple
+
+def structure_tensor(volume: np.ndarray,
+                     sigma: float,
+                     rho: float,
+                     full: bool = False,
+                     ) -> Tuple[np.ndarray, np.ndarray]:
+    """Wrapper for the 3D structure tensor implementation from the structure_tensor package (https://github.com/Skielex/structure-tensor/)
+
+    Args:
+        volume (np.ndarray): 3D NumPy array representing the volume.
+        sigma (float): A noise scale, structures smaller than sigma will be removed by smoothing.
+        rho (float): An integration scale giving the size over the neighborhood in which the orientation is to be analysed.
+        full: A flag indicating that all three eigenvalues should be returned. Default is False.
+        eigenvalue_order: The order of the eigenvalues. Either "desc" for descending or "asc" for ascending. Default is "desc".
+
+    Returns:
+        val: An array with shape `(3, *volume.shape)` containing the eigenvalues of the structure tensor.
+        vec: An array with shape `(3, ...)` if `full` is `False`, otherwise `(3, 3, ...)` containing eigenvectors.
+
+    !!! quote "Reference"
+        Jeppesen, N., et al. "Quantifying effects of manufacturing methods on fiber orientation in unidirectional composites using structure tensor analysis." Composites Part A: Applied Science and Manufacturing 149 (2021): 106541.
+        <https://doi.org/10.1016/j.compositesa.2021.106541>
+
+        ```bibtex
+        @article{JEPPESEN2021106541,
+        title = {Quantifying effects of manufacturing methods on fiber orientation in unidirectional composites using structure tensor analysis},
+        journal = {Composites Part A: Applied Science and Manufacturing},
+        volume = {149},
+        pages = {106541},
+        year = {2021},
+        issn = {1359-835X},
+        doi = {https://doi.org/10.1016/j.compositesa.2021.106541},
+        url = {https://www.sciencedirect.com/science/article/pii/S1359835X21002633},
+        author = {N. Jeppesen and L.P. Mikkelsen and A.B. Dahl and A.N. Christensen and V.A. Dahl}
+        }
+    """
+
+    S = st.structure_tensor_3d(volume, sigma, rho)
+    val, vec = st.eig_special_3d(S, full=full)
+
+    return val, vec
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