Creating a Magnifying Glass Effect in Silverlight
This article will show you the basics of creating a Silverlight magnifying glass control, where you will be able to position the cursor over an image and click to zoom in on the image portion under the cursor.
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The XAML here contains two image elements, the first is the original image and the second is the image as viewed through the magnifying glass. Notice how this has a scale transform applied to it:
<UserControl x:Class="MagnifyingGlass.Page"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Width="640" Height="480">
<Canvas x:Name="LayoutRoot" Background="White">
<Image x:Name="myImage" Width="320" Height="240" Source="reef.jpg" MouseMove="myImage_MouseMove" MouseLeftButtonDown="Image_MouseLeftButtonDown" MouseLeftButtonUp="Image_MouseLeftButtonUp" />
<Image x:Name="glass" Width="320" Height="240" Visibility="Collapsed" Source="reef.jpg" IsHitTestVisible="False">
<Image.RenderTransform>
<ScaleTransform ScaleX="2" ScaleY="2"/>
</Image.RenderTransform>
<Image.Clip>
<EllipseGeometry x:Name="geometry" RadiusX="40" RadiusY="40" />
</Image.Clip>
</Image>
</Canvas>
</UserControl>
In the C# we will need to handle the three mouse events MouseLeftButtonDown, MouseLeftButtonUp and MouseMove:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
namespace MagnifyingGlass
{
public partial class Page : UserControl
{
public Page()
{
InitializeComponent();
}
private void Image_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
glass.Visibility = Visibility.Visible;
UpdateGlassPosition(e.GetPosition(myImage));
}
private void Image_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
glass.Visibility = Visibility.Collapsed;
}
private void myImage_MouseMove(object sender, MouseEventArgs e)
{
UpdateGlassPosition(e.GetPosition(myImage));
}
private void UpdateGlassPosition(Point position)
{
geometry.Center = new Point(position.X, position.Y);
glass.SetValue(Canvas.LeftProperty, -position.X);
glass.SetValue(Canvas.TopProperty, -position.Y);
}
}
}
In the code we respond to the mouse events and calculate the position of the zoomed in area. The magnified area is only visible when the mouse button is pressed.
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