Render exclusion outlines on overlay preview

app/qt/main_window.py

@@ -929,7 +929,8 @@ class MainWindow(QtWidgets.QMainWindow, I18nMixin):
             self.image_view.set_pixmap(preview_pix)
             self.image_view.set_shapes(self.processor.exclude_shapes.copy())
             self.overlay_view.setText("")
-            self.overlay_view.setPixmap(overlay_pix)
+        overlay_pix = self._overlay_with_outlines(overlay_pix)
+        self.overlay_view.setPixmap(overlay_pix)
         if self._current_image_path and self.processor.preview_img:
             width, height = self.processor.preview_img.size
             total = len(self.processor.preview_paths)
@@ -952,9 +953,39 @@ class MainWindow(QtWidgets.QMainWindow, I18nMixin):
             self.overlay_view.setPixmap(QtGui.QPixmap())
         else:
             self.overlay_view.setText("")
-            self.overlay_view.setPixmap(pix)
+            self.overlay_view.setPixmap(self._overlay_with_outlines(pix))
         self.ratio_label.setText(self.processor.stats.summary(self._t))
 
     def _on_shapes_changed(self, shapes: list[dict[str, object]]) -> None:
         self.processor.set_exclusions(shapes)
         self._refresh_overlay_only()
+
+    def _overlay_with_outlines(self, pixmap: QtGui.QPixmap) -> QtGui.QPixmap:
+        if pixmap.isNull() or not self.processor.exclude_shapes:
+            return pixmap
+        result = QtGui.QPixmap(pixmap)
+        painter = QtGui.QPainter(result)
+        colour = QtGui.QColor(THEMES[self.current_theme]["highlight"])
+        pen = QtGui.QPen(colour)
+        pen.setWidth(3)
+        pen.setCosmetic(True)
+        pen.setCapStyle(QtCore.Qt.RoundCap)
+        pen.setJoinStyle(QtCore.Qt.RoundJoin)
+        painter.setPen(pen)
+        for shape in self.processor.exclude_shapes:
+            kind = shape.get("kind")
+            if kind == "rect":
+                x0, y0, x1, y1 = shape["coords"]  # type: ignore[index]
+                painter.drawRect(QtCore.QRectF(x0, y0, x1 - x0, y1 - y0))
+            elif kind == "polygon":
+                points = shape.get("points", [])
+                if len(points) >= 2:
+                    path = QtGui.QPainterPath()
+                    first = QtCore.QPointF(*points[0])
+                    path.moveTo(first)
+                    for px, py in points[1:]:
+                        path.lineTo(px, py)
+                    path.closeSubpath()
+                    painter.drawPath(path)
+        painter.end()
+        return result