clean up node naming

backend/nodes/level_poly.py

@@ -0,0 +1,50 @@
+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="Polynomial Level")
+class PolyLevelField:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "field": ("DATA_FIELD",),
+                "degree_x": ("INT", {"default": 2, "min": 0, "max": 5, "step": 1}),
+                "degree_y": ("INT", {"default": 2, "min": 0, "max": 5, "step": 1}),
+            }
+        }
+
+    OUTPUTS = (
+        ('DATA_FIELD', 'leveled'),
+        ('DATA_FIELD', 'background'),
+    )
+    FUNCTION = "process"
+
+    DESCRIPTION = (
+        "Fit and subtract a polynomial background of given degree in x and y. "
+        "Equivalent to gwy_data_field_fit_polynom."
+    )
+
+    def process(self, field: DataField, degree_x: int, degree_y: int) -> tuple:
+        data = field.data.copy()
+        yres, xres = data.shape
+
+        x = np.linspace(0.0, 1.0, xres)
+        y = np.linspace(0.0, 1.0, yres)
+        xx, yy = np.meshgrid(x, y)
+
+        cols = []
+        for i in range(degree_x + 1):
+            for j in range(degree_y + 1):
+                cols.append((xx ** i * yy ** j).ravel())
+        A = np.column_stack(cols)
+        z = data.ravel()
+
+        coeffs, _, _, _ = np.linalg.lstsq(A, z, rcond=None)
+
+        background = (A @ coeffs).reshape(yres, xres)
+        leveled = data - background
+
+        return (field.replace(data=leveled), field.replace(data=background))