add a few more nodes

backend/nodes/zero_value.py

@@ -0,0 +1,56 @@
+"""Zero Value — shift data so the mean or maximum equals zero."""
+
+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="Zero Mean")
+class ZeroMean:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "field": ("DATA_FIELD",),
+            }
+        }
+
+    OUTPUTS = (
+        ('DATA_FIELD', 'leveled'),
+    )
+    FUNCTION = "process"
+
+    DESCRIPTION = "Shift all values so the mean is exactly zero."
+
+    KEYWORDS = ("offset", "center", "level", "mean")
+
+    def process(self, field: DataField) -> tuple:
+        data = np.asarray(field.data, dtype=np.float64)
+        return (field.replace(data=data - data.mean()),)
+
+
+@register_node(display_name="Zero Maximum")
+class ZeroMaximum:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "field": ("DATA_FIELD",),
+            }
+        }
+
+    OUTPUTS = (
+        ('DATA_FIELD', 'leveled'),
+    )
+    FUNCTION = "process"
+
+    DESCRIPTION = "Shift all values so the maximum is exactly zero."
+
+    KEYWORDS = ("offset", "level", "maximum")
+
+    def process(self, field: DataField) -> tuple:
+        data = np.asarray(field.data, dtype=np.float64)
+        return (field.replace(data=data - data.max()),)