tip modelling and deconvolution

backend/nodes/gradient.py

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+from __future__ import annotations
+
+import numpy as np
+
+from backend.node_registry import register_node
+from backend.data_types import DataField
+
+
+@register_node(display_name="Gradient")
+class Gradient:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "field": ("DATA_FIELD",),
+                "component": (["magnitude", "x", "y", "azimuth"],),
+            }
+        }
+
+    OUTPUTS = (
+        ('DATA_FIELD', 'gradient'),
+    )
+    FUNCTION = "process"
+
+    DESCRIPTION = (
+        "Compute the spatial gradient using a Sobel operator. "
+        "'x'/'y' give the physical gradient components (z_unit/xy_unit); "
+        "'magnitude' gives sqrt(gx²+gy²); "
+        "'azimuth' gives the local slope direction in radians via atan2(gy, gx). "
+        "Equivalent to gwy_data_field_filter_sobel in Gwyddion (gradient.c)."
+    )
+
+    def process(self, field: DataField, component: str) -> tuple:
+        from scipy.ndimage import sobel
+
+        data = field.data
+        # Sobel kernel sums to ±8 over 2-pixel span; divide by 8·dx to get z/xy slope.
+        gx = sobel(data, axis=1) / (8.0 * field.dx)
+        gy = sobel(data, axis=0) / (8.0 * field.dy)
+
+        if component == "magnitude":
+            result = np.hypot(gx, gy)
+            z = str(field.si_unit_z or "").strip()
+            xy = str(field.si_unit_xy or "").strip()
+            out_unit_z = f"{z}/{xy}" if z and xy else (z or xy)
+        elif component == "x":
+            result = gx
+            z = str(field.si_unit_z or "").strip()
+            xy = str(field.si_unit_xy or "").strip()
+            out_unit_z = f"{z}/{xy}" if z and xy else (z or xy)
+        elif component == "y":
+            result = gy
+            z = str(field.si_unit_z or "").strip()
+            xy = str(field.si_unit_xy or "").strip()
+            out_unit_z = f"{z}/{xy}" if z and xy else (z or xy)
+        elif component == "azimuth":
+            # Azimuth: local slope direction, radians, matches Gwyddion's filter_azimuth
+            result = np.arctan2(gy, gx)
+            out_unit_z = "rad"
+        else:
+            raise ValueError(f"Unknown gradient component: {component!r}")
+
+        return (field.replace(data=result, si_unit_z=out_unit_z),)