feat(viz): implement RBF heatmap and custom QPainter trend chart item

Introduce Radial Basis Function interpolation for fine wafer thermal gradients and GraphQuickItem for high-performance trend line rendering.

src/pygui/backend/visualization/wafer_map_item.py

@@ -10,6 +10,7 @@ All sensor coordinates are center-origin mm (from wafer_layouts or a loaded CSV)
 """
 from __future__ import annotations
 
+import logging
 import math
 
 import numpy as np
@@ -22,13 +23,15 @@ from PySide6.QtGui import (
     QPainter,
     QPen,
     QPolygon,
-)
+)  # fmt: skip
 from PySide6.QtQml import QmlElement
 from PySide6.QtQuick import QQuickPaintedItem
 
 from pygui.backend.visualization.rbf_heatmap import interpolate_field
 from pygui.backend.wafer.zwafer_models import Sensor
 
+log = logging.getLogger(__name__)
+
 QML_IMPORT_NAME = "ISC.Wafer"
 QML_IMPORT_MAJOR_VERSION = 1
 
@@ -197,10 +200,10 @@ class WaferMapItem(QQuickPaintedItem):
     def thicknessData(self, val:list) -> None:
         self._thickness_data = list(val or [])
         self._rebuild_thickness()
-        self._thicknessChanged.emit()
+        self.thicknessChanged.emit()
         self.update
 
-    @property(bool, notify=showThicknessChanged)
+    @Property(bool, notify=showThicknessChanged)
     def showThickness(self) -> bool:
         return self._show_thickness
 
@@ -265,14 +268,59 @@ class WaferMapItem(QQuickPaintedItem):
         if not file_path:
             return False
         try:
-            image = self.grabToImage()
-            image.save(file_path, "PNG")
+            result = self.grabToImage()
+            img = result.image()
+            img.save(file_path, "PNG")
             return True
         except Exception as e:
             log.error("Export failed: %s", e)
             return False
+
     # ── internal ─────────────────────────────────────────────────────────
 
+    def _rebuild_thickness(self) -> None:
+        """Interpolate thickness data into a gray/orange heatmap QImage."""
+        if not self._sensors or not self._thickness_data:
+            self._thickness_heatmap = None
+            return
+        ds = self._draw_size()
+        r_mm = self._wafer_radius_mm()
+        xs = np.array([s.x for s in self._sensors])
+        ys = np.array([s.y for s in self._sensors])
+        vs = np.array(self._thickness_data[:len(self._sensors)], dtype=float)
+        if len(vs) < len(self._sensors):
+            self._thickness_heatmap = None
+            return
+        try:
+            field = interpolate_field(
+                xs, ys, vs,
+                width=ds, height=ds,
+                extent=(-r_mm, r_mm, -r_mm, r_mm),
+                round_clip=(self._shape == "round"),
+            )
+        except Exception:
+            self._thickness_heatmap = None
+            return
+        # Gray/orange colormap: map field range 0→1 to gray→orange
+        vmin, vmax = np.nanmin(field), np.nanmax(field)
+        span = vmax - vmin or 1.0
+        t = np.clip((field - vmin) / span, 0.0, 1.0)
+
+        # Gray (0.5, 0.5, 0.5) → orange (1.0, 0.65, 0.0)
+        rgb = np.zeros((ds, ds, 3), dtype=np.float32)
+        rgb[:, :, 0] = 0.5 + 0.5 * t
+        rgb[:, :, 1] = 0.5 + 0.15 * t
+        rgb[:, :, 2] = 0.5 - 0.5 * t
+
+        rgb = np.nan_to_num(rgb, nan=0.0)
+        rgba = np.zeros((ds, ds, 4), dtype=np.uint8)
+        rgba[:, :, :3] = (rgb * 255).astype(np.uint8)
+        rgba[:, :, 3] = np.where(np.isfinite(field), 180, 0).astype(np.uint8)
+
+        self._thickness_heatmap = (
+            QImage(rgba.tobytes(), ds, ds, QImage.Format.Format_RGBA8888).copy()
+        )
+
     def _on_resize(self) -> None:
         self._rebuild()