refactor nodes into standalone file

backend/nodes/draw_mask.py

@@ -0,0 +1,56 @@
+from __future__ import annotations
+import numpy as np
+from backend.node_registry import register_node
+from backend.data_types import DataField, datafield_to_uint8, encode_preview
+from backend.nodes.helpers import _parse_mask_strokes, _rasterize_mask
+
+
+@register_node(display_name="Draw Mask")
+class DrawMask:
+    _CUSTOM_PREVIEW = True
+
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "field": ("DATA_FIELD",),
+                "pen_size": ("INT", {"default": 12, "min": 1, "max": 128, "step": 1}),
+                "invert": ("BOOLEAN", {"default": False}),
+                "clear_mask": ("BUTTON", {"label": "Clear Mask", "set_widgets": {"mask_paths": "[]"}}),
+                "mask_paths": ("STRING", {"default": "[]", "hidden": True}),
+            }
+        }
+
+    RETURN_TYPES = ("IMAGE",)
+    RETURN_NAMES = ("mask",)
+    FUNCTION = "process"
+
+    DESCRIPTION = (
+        "Paint a binary mask directly over an image preview. "
+        "Pen size controls newly drawn strokes, the overlay lets you clear the mask, "
+        "and invert flips the final binary output."
+    )
+
+    _broadcast_overlay_fn = None
+    _current_node_id: str = ""
+
+    def process(self, field: DataField, pen_size: int, invert: bool, mask_paths: str) -> tuple:
+        strokes = _parse_mask_strokes(mask_paths)
+        mask = _rasterize_mask(field.xres, field.yres, strokes, pen_size)
+        if invert:
+            mask = np.where(mask > 127, np.uint8(0), np.uint8(255))
+
+        if DrawMask._broadcast_overlay_fn is not None:
+            DrawMask._broadcast_overlay_fn(
+                DrawMask._current_node_id,
+                {
+                    "kind": "mask_paint",
+                    "section_title": "Mask",
+                    "image": encode_preview(datafield_to_uint8(field, "gray")),
+                    "image_width": field.xres,
+                    "image_height": field.yres,
+                    "invert": bool(invert),
+                },
+            )
+
+        return (mask,)