Use a VisualBrush to magnify a portion of the screen. : Brush « Windows Presentation Foundation « C# / C Sharp

1. C# / C Sharp
2. Windows Presentation Foundation
3. Brush

Use a VisualBrush to magnify a portion of the screen.

  

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
  x:Class="Microsoft.Samples.Graphics.UsingVisualBrush.MagnifyingGlassExample"
  Background="White">
  <Page.Resources>
    <Style TargetType="{x:Type Paragraph}">
      <Setter Property="Margin" Value="10" />
    </Style>
    <DrawingBrush x:Key="MyGridBackgroundBrushResource"
      Viewport="0,0,10,10" ViewportUnits="Absolute" TileMode="Tile">
      <DrawingBrush.Drawing>
        <DrawingGroup>
          <DrawingGroup.Children>
            <GeometryDrawing Brush="White">
              <GeometryDrawing.Geometry>
                <RectangleGeometry Rect="0,0,1,1" />
              </GeometryDrawing.Geometry>
            </GeometryDrawing>
            <GeometryDrawing Brush="#E6E8F6"
              Geometry="M 0,0 L 0,1 0.1,1 0.1,0.1 1,0.1 1,0 Z" />                      
          </DrawingGroup.Children>
        </DrawingGroup>
      </DrawingBrush.Drawing>
    </DrawingBrush>   
    
  </Page.Resources>

  <Grid>  
    <ScrollViewer>
      <StackPanel Name="magnifiedPanel" 
        VerticalAlignment="Stretch"
        MouseMove="updateMagnifyingGlass" 
        Background="{StaticResource MyGridBackgroundBrushResource}">
        
        <FlowDocumentScrollViewer>
        <FlowDocument>
<Paragraph><Button></Button></Paragraph>

<Paragraph><Border BorderBrush="Black" BorderThickness="1"><Image Source="c:\image.jpg" Stretch="None" /></Border></Paragraph>

<Paragraph>this is a test</Paragraph> 
        </FlowDocument>
        </FlowDocumentScrollViewer>
      </StackPanel>
    </ScrollViewer>
    <Canvas Name="magnifyingGlassCanvas">
      <Ellipse Name="magnifyingGlassEllipse" Width="100" Height="100" Stroke="Black">
        <Ellipse.Fill>
          <DrawingBrush>
            <DrawingBrush.Drawing>
              <DrawingGroup>
                <DrawingGroup.Children>
                   <GeometryDrawing Brush="White">
                    <GeometryDrawing.Geometry>
                      <RectangleGeometry Rect="0,0,1,1" />
                    </GeometryDrawing.Geometry>
                  </GeometryDrawing>
                   <GeometryDrawing>
                    <GeometryDrawing.Brush>
                       <VisualBrush x:Name="myVisualBrush" ViewboxUnits="Absolute"
                        Visual="{Binding ElementName=magnifiedPanel}"/>
                    </GeometryDrawing.Brush>
                    <GeometryDrawing.Geometry>
                      <RectangleGeometry Rect="0,0,1,1" />
                    </GeometryDrawing.Geometry>
                  </GeometryDrawing>
                </DrawingGroup.Children>
              </DrawingGroup>
            </DrawingBrush.Drawing>
          </DrawingBrush>
        </Ellipse.Fill>
      </Ellipse>
    </Canvas>
  </Grid>
</Page>

//File:Window.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Media;
using System.Windows.Input;

namespace Microsoft.Samples.Graphics.UsingVisualBrush
{
    public partial class MagnifyingGlassExample : Page
    {
        private static readonly double distanceFromMouse = 5;
        
        public MagnifyingGlassExample()
        {
        }
        private void updateMagnifyingGlass(object sender, MouseEventArgs args)
        {
            Mouse.SetCursor(Cursors.Cross);
            Point currentMousePosition = args.GetPosition(this);
            if (this.ActualWidth - currentMousePosition.X > magnifyingGlassEllipse.Width + distanceFromMouse)
            {
                Canvas.SetLeft(magnifyingGlassEllipse, currentMousePosition.X + distanceFromMouse);
            }
            else
            {
                Canvas.SetLeft(magnifyingGlassEllipse, currentMousePosition.X - distanceFromMouse - magnifyingGlassEllipse.Width);
            }
            
            if (this.ActualHeight - currentMousePosition.Y > magnifyingGlassEllipse.Height + distanceFromMouse)
            {
                Canvas.SetTop(magnifyingGlassEllipse, currentMousePosition.Y + distanceFromMouse);
            }
            else
            {
                Canvas.SetTop(magnifyingGlassEllipse, currentMousePosition.Y - distanceFromMouse - magnifyingGlassEllipse.Height);
            }
            myVisualBrush.Viewbox = new Rect(currentMousePosition.X - 10, currentMousePosition.Y  - 10, 20, 20);
        }
    }
}

   
    
  

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