Add local area adjustment feature to image editor

Introduced a LocalAdjustmentRectangle for region selection and a checkbox to toggle local/global adjustments. Refactored image adjustment handlers to support applying effects to either the whole image or a selected area, improving editing flexibility. Added SetAppearance method for rectangle customization.

Author: TheJoeFin

MagickCrop/Controls/ResizableRectangle.xaml.cs

@@ -32,6 +32,17 @@ public MagickGeometry CropShape
         (uint)rectangle.ActualHeight);
     }
 
+    /// <summary>
+    /// Sets the stroke color and optionally hides the fill of the inner rectangle.
+    /// </summary>
+    public void SetAppearance(System.Windows.Media.Brush stroke, bool showFill)
+    {
+        rectangle.Stroke = stroke;
+        rectangle.Fill = showFill
+            ? new System.Windows.Media.SolidColorBrush(System.Windows.Media.Colors.Blue) { Opacity = 0.06 }
+            : null;
+    }
+
     private void UserControl_MouseMove(object sender, MouseEventArgs e)
     {
         if (Mouse.LeftButton == MouseButtonState.Released

MagickCrop/MainWindow.xaml

@@ -234,6 +234,7 @@
                     Visibility="Collapsed" />
 
                 <local:ResizableRectangle x:Name="CroppingRectangle" Visibility="Collapsed" />
+                <local:ResizableRectangle x:Name="LocalAdjustmentRectangle" Visibility="Collapsed" />
             </Canvas>
 
             <!--  Pixel Precision Zoom Control - Outside ShapeCanvas to avoid being affected by canvas zoom  -->
@@ -570,6 +571,14 @@
                                     <wpfui:SymbolIcon Symbol="ImageEdit24" ToolTip="Adjust image appearance" />
                                 </TabItem.Header>
                                 <StackPanel Orientation="Vertical">
+                                    <CheckBox
+                                        x:Name="LocalAdjustmentCheckBox"
+                                        Margin="0,4"
+                                        Checked="LocalAdjustmentCheckBox_Checked"
+                                        Content="Local Area"
+                                        IsChecked="False"
+                                        ToolTip="When checked, adjustments apply only to the selected region"
+                                        Unchecked="LocalAdjustmentCheckBox_Unchecked" />
                                     <MenuItem
                                         Name="AutoContrastMenuItem"
                                         Click="AutoContrastMenuItem_Click"