探测器设置界面增加图像灰度直方图，用于显示实时采集图像的灰度信息，优化图像灰度直方图的显示方式（无图像提示）和优化资源释放。

XP.Common/Controls/ImageHistogram/ImageHistogramControl.xaml

@@ -2,12 +2,18 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
+             xmlns:loc="clr-namespace:XP.Common.Localization.Extensions"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
              mc:Ignorable="d"
              d:DesignHeight="200" d:DesignWidth="400">
     <Grid>
+        <!-- 图表控件 | Chart control -->
         <telerik:RadCartesianChart x:Name="HistogramChart">
+            <!-- 禁用 Telerik 自带的无数据提示 | Disable Telerik built-in empty content -->
+            <telerik:RadCartesianChart.EmptyContent>
+                <TextBlock/>
+            </telerik:RadCartesianChart.EmptyContent>
             <!-- X 轴：灰度级别 | X Axis: Gray Level -->
             <telerik:RadCartesianChart.HorizontalAxis>
                 <telerik:LinearAxis x:Name="XAxis"
@@ -32,5 +38,14 @@
                                    ShowLabels="False"/>
             </telerik:RadCartesianChart.Series>
         </telerik:RadCartesianChart>
+
+        <!-- 无数据提示文本（叠加在图表上方）| No data placeholder text (overlaid on chart) -->
+        <TextBlock x:Name="NoDataPlaceholder"
+                   Text="{loc:Localization Histogram_NoData}"
+                   HorizontalAlignment="Center"
+                   VerticalAlignment="Center"
+                   FontSize="14"
+                   Foreground="#9E9E9E"
+                   Visibility="Visible"/>
     </Grid>
 </UserControl>

XP.Common/Controls/ImageHistogram/ImageHistogramControl.xaml.cs

@@ -219,10 +219,24 @@ namespace XP.Common.Controls.ImageHistogram
                 // 取消帧率限流器中的待处理任务 | Cancel pending tasks in throttler
                 _frameThrottler.Cancel();
 
-                // 清空图表 | Clear chart
-                if (_chartRenderer != null)
+                // 清空图表（捕获局部引用避免异步执行时为 null）| Clear chart (capture local ref to avoid null during async)
+                var renderer = _chartRenderer;
+                if (renderer != null)
                 {
-                    Dispatcher.InvokeAsync(() => _chartRenderer.Clear());
+                    Dispatcher.InvokeAsync(() =>
+                    {
+                        try
+                        {
+                            renderer.Clear();
+
+                            // 显示无数据提示 | Show no-data placeholder
+                            NoDataPlaceholder.Visibility = Visibility.Visible;
+                        }
+                        catch
+                        {
+                            // 控件已卸载时忽略 | Ignore if control already unloaded
+                        }
+                    });
                 }
             }
             catch (Exception ex)
@@ -259,6 +273,9 @@ namespace XP.Common.Controls.ImageHistogram
                                 {
                                     isLog = IsLogarithmic;
                                     _chartRenderer?.UpdateData(histogram, isLog);
+
+                                    // 隐藏无数据提示 | Hide no-data placeholder
+                                    NoDataPlaceholder.Visibility = Visibility.Collapsed;
                                 }
                                 catch (Exception ex)
                                 {

XP.Common/Resources/Resources.en-US.resx

@@ -1887,4 +1887,8 @@ Reprojection error: {1:F4} pixels</value>
   <data name="ChessboardImageError" xml:space="preserve">
     <value>Image{0}: {1:F4} pixels</value>
   </data>
+  <data name="Histogram_NoData" xml:space="preserve">
+    <value>Histogram — No data</value>
+    <comment>ImageHistogramControl - Placeholder text when no image data</comment>
+  </data>
 </root>

XP.Common/Resources/Resources.resx

@@ -1920,4 +1920,8 @@
   <data name="ChessboardImageError" xml:space="preserve">
     <value>图像{0}: {1:F4} 像素</value>
   </data>
+  <data name="Histogram_NoData" xml:space="preserve">
+    <value>直方图 — 暂无数据</value>
+    <comment>ImageHistogramControl - 无图像输入时的提示文本 | Placeholder text when no image data</comment>
+  </data>
 </root>

XP.Common/Resources/Resources.zh-CN.resx

@@ -1881,4 +1881,8 @@
   <data name="ChessboardImageError" xml:space="preserve">
     <value>图像{0}: {1:F4} 像素</value>
   </data>
+  <data name="Histogram_NoData" xml:space="preserve">
+    <value>直方图 — 暂无数据</value>
+    <comment>ImageHistogramControl - 无图像输入时的提示文本 | Placeholder text when no image data</comment>
+  </data>
 </root>

XP.Common/Resources/Resources.zh-TW.resx

@@ -1881,4 +1881,8 @@
   <data name="ChessboardImageError" xml:space="preserve">
     <value>图像{0}: {1:F4} 像素</value>
   </data>
+  <data name="Histogram_NoData" xml:space="preserve">
+    <value>直方圖 — 暫無資料</value>
+    <comment>ImageHistogramControl - 無圖像輸入時的提示文字 | Placeholder text when no image data</comment>
+  </data>
 </root>