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UseDpi Property (ImageBox)

Summary

Gets or sets a value that indicates whether the control must account for the physical resolution of the image when calculating the display properties. This is a dependency property.

Syntax

C++

public bool UseDpi {get; set;}

Public Property UseDpi As Boolean

public: 
property bool UseDpi { 
   bool get(); 
   void set (    bool ); 
}

Property Value

true to account for the physical resolution of the image when calculating the display properties; otherwise, false.

Remarks

The physical resolution of an image is measured in dots per inch (DPI). When you load an image, the Leadtools.RasterImage.XResolution and Leadtools.RasterImage.YResolution properties are updated with the DPI values for the horizontal and vertical resolution. Some images have different horizontal and vertical resolutions. For example, the horizontal resolution of a fax image is typically twice its vertical resolution (for example 200 by 100). In such cases, the displayed images will appear elongated if you do not account for the resolution. If the image horizontal and vertical and resolution are is ot equal, you must set the UseDpi property to true to have the control automated scaling properties account for the physical resolution of the image.

The values of SourceDpiX, SourceDpiY, ScreenDpiX and ScreenDpiY are used when calculating how to display the image if the value of UseDpi is set to true.

For example, a typical A4 document image is 8.5 by 11 inches. Which could be 2550 by 3300 pixels if the image has a resolution of 300 by 300. Most document viewer applications will try to display this image in its original size. i.e. the image will take 8.5 inches of screen horizontal space and 11 inches of screen vertical space. Without using the UseDpi property of this control, you are required to do the calculations yourself as follows:

control.UseDpi = false; 
control.ScaleFactor = screenResolution / imageResolution;

In the case of the image above, this will be 96 (typical screen resolution) divided by 300. Or, you can set the UseDpi value to true and the control will use the above formula internally keeping the ScaleFactor set to 1 as follows:

control.UseDpi = true; 
control.ScaleFactor = 1;

This code will produce the same result as the previous one.

The control will automatically set the ScreenDpiX and ScreenDpiY to the current screen resolution, also the SourceDpiX and SourceDpiY will be obtained from the current image set in Source. You can change these values if required for manual calculations.

Example

Silverlight C#

Silverlight VB

Imports Leadtools.Windows.Controls 
 
Private Class MyWindow1 : Inherits Window 
    Private theImage As ImageBox 
    Public Sub New() 
        ' Create the  viewer 
        theImage = New ImageBox() 
 
        ' Create Dock Panel 
 
        Dim panel As DockPanel = New DockPanel() 
        Content = panel 
 
        DockPanel.SetDock(theImage, Dock.Bottom) 
 
        theImage.HorizontalAlignment = HorizontalAlignment.Center 
        theImage.VerticalAlignment = VerticalAlignment.Bottom 
        theImage.UseDpi = True 
        theImage.ScreenDpiX = 96 
        theImage.ScreenDpiY = 96 
 
        panel.Children.Add(theImage) 
 
        ' load an image into the viewer 
        theImage.Source = New BitmapImage(New Uri(Path.Combine(LEAD_VARS.ImagesDir, "cannon.jpg"))) 
 
        Title = String.Format("Size mode = {0}, click to change", theImage.SizeMode) 
 
        AddHandler theImage.MouseDown, AddressOf theImage_MouseClick 
    End Sub 
 
    Private Sub theImage_MouseClick(ByVal sender As Object, ByVal e As MouseButtonEventArgs) 
        Select Case theImage.SizeMode 
            Case SizeMode.Normal 
                theImage.SizeMode = SizeMode.Stretch 
 
            Case SizeMode.Stretch 
                theImage.SizeMode = SizeMode.Fit 
 
            Case SizeMode.Fit 
                theImage.SizeMode = SizeMode.FitAlways 
 
            Case SizeMode.FitAlways 
                theImage.SizeMode = SizeMode.FitWidth 
 
            Case SizeMode.FitWidth 
                theImage.SizeMode = SizeMode.Normal 
        End Select 
 
        Title = String.Format("Size mode = {0}, double click to change", theImage.SizeMode) 
 
    End Sub 
End Class 
 
Public NotInheritable Class LEAD_VARS 
Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images" 
End Class

using Leadtools.Help; 
using Leadtools.Windows.Controls; 
 
class MyWindow1 : Window 
{ 
   ImageBox theImage; 
   public MyWindow1() 
   { 
      // Create the  viewer 
      theImage = new ImageBox(); 
 
      // Create Dock Panel 
 
      DockPanel panel = new DockPanel(); 
      Content = panel; 
 
      DockPanel.SetDock(theImage, Dock.Bottom); 
 
      theImage.HorizontalAlignment = HorizontalAlignment.Center; 
      theImage.VerticalAlignment= VerticalAlignment.Bottom; 
      theImage.UseDpi = true; 
      theImage.ScreenDpiX = 96; 
      theImage.ScreenDpiY = 96; 
 
      panel.Children.Add(theImage); 
 
      // load an image into the viewer 
      theImage.Source = new BitmapImage(new Uri(Path.Combine(LEAD_VARS.ImagesDir, "cannon.jpg"))); 
 
      Title = string.Format("Size mode = {0}, click to change", theImage.SizeMode); 
 
      theImage.MouseDown += new MouseButtonEventHandler(theImage_MouseClick); 
   } 
 
   void theImage_MouseClick(object sender, MouseButtonEventArgs e) 
   { 
      switch(theImage.SizeMode) 
      { 
         case SizeMode.Normal: 
            theImage.SizeMode = SizeMode.Stretch; 
            break; 
 
         case SizeMode.Stretch: 
            theImage.SizeMode = SizeMode.Fit; 
            break; 
 
         case SizeMode.Fit: 
            theImage.SizeMode = SizeMode.FitAlways; 
            break; 
 
         case SizeMode.FitAlways: 
            theImage.SizeMode = SizeMode.FitWidth; 
            break; 
 
         case SizeMode.FitWidth: 
            theImage.SizeMode = SizeMode.Normal; 
            break; 
      } 
 
      Title = string.Format("Size mode = {0}, double click to change", theImage.SizeMode); 
 
   } 
} 
 
static class LEAD_VARS 
{ 
public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images"; 
}

using Leadtools.Help; 
using Leadtools.Windows.Controls; 
 
class MyWindow1 : ChildWindow 
{ 
   ImageBox theImage; 
   public MyWindow1() 
   { 
      // Create the  viewer 
      theImage = new ImageBox(); 
 
      // Create Dock Panel 
 
      StackPanel panel = new StackPanel(); 
      Content = panel; 
 
      theImage.HorizontalAlignment = HorizontalAlignment.Center; 
      theImage.VerticalAlignment= VerticalAlignment.Bottom; 
      theImage.UseDpi = true; 
      theImage.ScreenDpiX = 96; 
      theImage.ScreenDpiY = 96; 
 
      panel.Children.Add(theImage); 
 
      // load an image into the viewer 
      theImage.Source = new BitmapImage(new Uri(LeadtoolsExamples.Common.ImagesPath.Path + "cannon.jpg")); 
 
      Title = string.Format("Size mode = {0}, click to change", theImage.SizeMode); 
 
      theImage.MouseLeftButtonDown +=new MouseButtonEventHandler(theImage_MouseLeftButtonDown); 
   } 
 
   void theImage_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) 
   { 
      switch (theImage.SizeMode) 
      { 
         case SizeMode.Normal: 
            theImage.SizeMode = SizeMode.Stretch; 
            break; 
 
         case SizeMode.Stretch: 
            theImage.SizeMode = SizeMode.Fit; 
            break; 
 
         case SizeMode.Fit: 
            theImage.SizeMode = SizeMode.FitAlways; 
            break; 
 
         case SizeMode.FitAlways: 
            theImage.SizeMode = SizeMode.FitWidth; 
            break; 
 
         case SizeMode.FitWidth: 
            theImage.SizeMode = SizeMode.Normal; 
            break; 
      } 
 
      Title = string.Format("Size mode = {0}, double click to change", theImage.SizeMode); 
   } 
}

Imports Leadtools.Windows.Controls 
 
Private Class MyWindow1 : Inherits ChildWindow 
   Private theImage As ImageBox 
   Public Sub New() 
      ' Create the  viewer 
      theImage = New ImageBox() 
 
      ' Create Dock Panel 
 
      Dim panel As StackPanel = New StackPanel() 
      Content = panel 
 
      theImage.HorizontalAlignment = HorizontalAlignment.Center 
      theImage.VerticalAlignment= VerticalAlignment.Bottom 
      theImage.UseDpi = True 
      theImage.ScreenDpiX = 96 
      theImage.ScreenDpiY = 96 
 
      panel.Children.Add(theImage) 
 
      ' load an image into the viewer 
      theImage.Source = New BitmapImage(New Uri(LeadtoolsExamples.Common.ImagesPath.Path & "cannon.jpg")) 
 
      Title = String.Format("Size mode = {0}, click to change", theImage.SizeMode) 
 
      AddHandler theImage.MouseLeftButtonDown, AddressOf theImage_MouseLeftButtonDown 
   End Sub 
 
   Private Sub theImage_MouseLeftButtonDown(ByVal sender As Object, ByVal e As MouseButtonEventArgs) 
      Select Case theImage.SizeMode 
         Case SizeMode.Normal 
            theImage.SizeMode = SizeMode.Stretch 
 
         Case SizeMode.Stretch 
            theImage.SizeMode = SizeMode.Fit 
 
         Case SizeMode.Fit 
            theImage.SizeMode = SizeMode.FitAlways 
 
         Case SizeMode.FitAlways 
            theImage.SizeMode = SizeMode.FitWidth 
 
         Case SizeMode.FitWidth 
            theImage.SizeMode = SizeMode.Normal 
      End Select 
 
      Title = String.Format("Size mode = {0}, double click to change", theImage.SizeMode) 
   End Sub 
End Class

<!--WPF example--> 
 <Window x:Class="WPFSamples.ImageBox" 
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
 xmlns:Leadtools_Windows_Controls="clr-namespace:Leadtools.Windows.Controls;assembly=Leadtools.Windows.Controls" 
 Height="600" Width="800"> 
   <DockPanel> 
     <Leadtools_Windows_Controls:ImageBox 
     Name="theImage" 
   Source="file:///c:\users\Public\Documents\LEADTOOLS Images\cannon.jpg" 
   DockPanel.Dock= "Bottom" 
   HorizontalAlignment="Center" VerticalAlignment="Bottom" SizeMode="Fit" UseDpi="true"> 
 
     </Leadtools_Windows_Controls:ImageBox > 
   </DockPanel> 
   <Window.Title> 
     "Apply a effect" 
   </Window.Title> 
 </Window> 
  
 <!--Silverlight example--> 
 <UserControl x:Class="SilverlightApplication1.MainPage" 
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
 xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
 xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
 xmlns:Leadtools_Windows_Controls="clr-namespace:Leadtools.Windows.Controls;assembly=Leadtools.Windows.Controls" 
 mc:Ignorable="d" 
 d:DesignHeight="300" d:DesignWidth="400"> 
   <Grid x:Name="LayoutRoot" Background="White"> 
      <Leadtools_Windows_Controls:ImageBox Name="theImage" Source="http://www.MyServer.com/images/MyImage.png" HorizontalAlignment="Center" VerticalAlignment="Bottom" SizeMode="Fit" UseDpi="true"> 
      </Leadtools_Windows_Controls:ImageBox > 
   </Grid> 
</UserControl>