diff --git a/src/gui/panels/step12_viz_panel.py b/src/gui/panels/step12_viz_panel.py
index ed9d03b..ea73a64 100644
--- a/src/gui/panels/step12_viz_panel.py
+++ b/src/gui/panels/step12_viz_panel.py
@@ -978,12 +978,18 @@ class ImageViewerWidget(QWidget):
         layout.addLayout(toolbar)
 
         self.scroll_area = QScrollArea()
-        self.scroll_area.setWidgetResizable(True)
+        # setWidgetResizable(False): QLabel 保持自身 pixmap 固有尺寸，
+        # 放大时自然超出视口触发滚动条，而非被 QScrollArea 强制压缩
+        self.scroll_area.setWidgetResizable(False)
+        self.scroll_area.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
+        self.scroll_area.setHorizontalScrollBarPolicy(Qt.ScrollBarAsNeeded)
+        self.scroll_area.setVerticalScrollBarPolicy(Qt.ScrollBarAsNeeded)
         self.scroll_area.setStyleSheet("background-color: white;")
 
         self.image_label = QLabel()
         self.image_label.setAlignment(Qt.AlignCenter)
-        self.image_label.setStyleSheet("background-color:  white;")
+        self.image_label.setSizePolicy(QSizePolicy.Ignored, QSizePolicy.Ignored)
+        self.image_label.setStyleSheet("background-color: white;")
 
         self.scroll_area.setWidget(self.image_label)