AutoDisposeImages Property (RasterImageViewer)

Gets or sets a value indicating whether to auto dispose the old image when a new image is set into this RasterImageViewer.

Syntax

C#
Visual Basic
Objective-C
Java
C++

[DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")]
[CategoryAttribute("Behavior")]
public virtual bool AutoDisposeImages {get; set;}

'Declaration
 
<DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")>
<CategoryAttribute("Behavior")>
Public Overridable Property AutoDisposeImages As Boolean

'Usage
 
Dim instance As RasterImageViewer
Dim value As Boolean
 
instance.AutoDisposeImages = value
 
value = instance.AutoDisposeImages

[DescriptionAttribute("Indicating whether to auto dispose the old image when a new image is set into this control")]
[CategoryAttribute("Behavior")]
public:
virtual property bool AutoDisposeImages {
   bool get();
   void set (    bool value);
}

Property Value

true if the image in Image is automatically disposed when a new image is set; otherwise, false. Default value is true.

Remarks

By default, whenever you set a new image into the Image property, the old image (if any) is disposed. Set the value of this property to false to prevent disposing of the old image.

Example

C#
Visual Basic
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools.WinForms
Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing.Color
Imports Leadtools.Drawing

Private Sub viewer_ImageChanged(ByVal sender As Object, ByVal e As EventArgs)
   Dim viewer As RasterImageViewer = CType(IIf(TypeOf sender Is RasterImageViewer, sender, Nothing), RasterImageViewer)
   Dim s As String
   If Not viewer.Image Is Nothing Then
      s = String.Format("Image Changed: New Width {0}, NewHeight {1}", viewer.Image.Width, viewer.Image.Height)
   Else
      s = "No Image"
   End If
   Console.WriteLine(s)
End Sub

Public Sub RasterImageViewer_AutoDisposeImages(ByVal viewer As RasterImageViewer)
   ' Load two image2
   Dim codecs As RasterCodecs = New RasterCodecs()
   Dim file1 As String = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp")
   Dim file2 As String = Path.Combine(LEAD_VARS.ImagesDir, "Image2.cmp")

   AddHandler viewer.ImageChanged, AddressOf viewer_ImageChanged

   Dim image1 As RasterImage = codecs.Load(file1)
   Dim image2 As RasterImage = codecs.Load(file2)

   ' Make sure the AutoDisposeImages property of the viewer is set to true
   viewer.AutoDisposeImages = True

   ' Set the first image into the viewer
   viewer.Image = image1

   ' Now set the second image into the viewer (this disposes the first image since the AutoDisposeImages property is true)
   viewer.Image = image2

   ' Try to access the first image, it generates a NullReferenceException exception since the image has been disposed
   MessageBox.Show("Try to access the first image, it generates a NullReferenceException exception since the image has been disposed.")
   Try
      Dim width As Integer = image1.Width
      MessageBox.Show(String.Format("Width is {0} pixels", width))
   Catch ex As NullReferenceException
      MessageBox.Show(ex.Message)
   End Try

   ' Set the image to null (will dispose the second image as well)
   viewer.Image = Nothing

   ' Now re-load the two images
   image1 = codecs.Load(file1)
   image2 = codecs.Load(file2)

   ' Make sure the AutoDisposeImages property of the viewer is set to false
   viewer.AutoDisposeImages = False

   ' Set the first image into the viewer
   viewer.Image = image1

   ' Now set the second image into the viewer (this will not disposes the first image since the AutoDisposeImages property is false)
   viewer.Image = image2

   ' Try to access the first image, it should work fine this time
   Try
      Dim width As Integer = image1.Width
      MessageBox.Show(String.Format("Width is {0} pixels", width))
   Catch ex As NullReferenceException
      MessageBox.Show(ex.Message)
   End Try

   ' Set the image to null (will not dispose the second image)
   viewer.Image = Nothing

   ' We should now dispose the two images manually
   image1.Dispose()
   image2.Dispose()

   RemoveHandler viewer.ImageChanged, AddressOf viewer_ImageChanged
End Sub

Public NotInheritable Class LEAD_VARS
Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

using Leadtools.WinForms;
using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing.Color;
using Leadtools.Drawing;

private void viewer_ImageChanged(object sender, EventArgs e)
{
   RasterImageViewer viewer = sender as RasterImageViewer;
   string s;
   if (viewer.Image != null)
      s = string.Format("Image Changed: New Width {0}, NewHeight {1}", viewer.Image.Width, viewer.Image.Height);
   else s = "No Image";
   Console.WriteLine(s);
}

public void RasterImageViewer_AutoDisposeImages(RasterImageViewer viewer)
{
   // Load two image2
   RasterCodecs codecs = new RasterCodecs();
   string file1 = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp");
   string file2 = Path.Combine(LEAD_VARS.ImagesDir, "Image2.cmp");

   viewer.ImageChanged += new EventHandler(viewer_ImageChanged);

   RasterImage image1 = codecs.Load(file1);
   RasterImage image2 = codecs.Load(file2);

   // Make sure the AutoDisposeImages property of the viewer is set to true
   viewer.AutoDisposeImages = true;

   // Set the first image into the viewer
   viewer.Image = image1;

   // Now set the second image into the viewer (this disposes the first image since the AutoDisposeImages property is true)
   viewer.Image = image2;

   // Try to access the first image, it generates a NullReferenceException exception since the image has been disposed
   MessageBox.Show("Try to access the first image, it generates a NullReferenceException exception since the image has been disposed.");
   try
   {
      int width = image1.Width;
      MessageBox.Show(string.Format("Width is {0} pixels", width));
   }
   catch (NullReferenceException ex)
   {
      MessageBox.Show(ex.Message);
   }

   // Set the image to null (will dispose the second image as well)
   viewer.Image = null;

   // Now re-load the two images
   image1 = codecs.Load(file1);
   image2 = codecs.Load(file2);

   // Make sure the AutoDisposeImages property of the viewer is set to false
   viewer.AutoDisposeImages = false;

   // Set the first image into the viewer
   viewer.Image = image1;

   // Now set the second image into the viewer (this will not disposes the first image since the AutoDisposeImages property is false)
   viewer.Image = image2;

   // Try to access the first image, it should work fine this time
   try
   {
      int width = image1.Width;
      MessageBox.Show(string.Format("Width is {0} pixels", width));
   }
   catch (NullReferenceException ex)
   {
      MessageBox.Show(ex.Message);
   }

   // Set the image to null (will not dispose the second image)
   viewer.Image = null;

   // We should now dispose the two images manually
   image1.Dispose();
   image2.Dispose();

   viewer.ImageChanged -= new EventHandler(viewer_ImageChanged);
}

static class LEAD_VARS
{
public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

Requirements

Target Platforms

Reference

RasterImageViewer Class
RasterImageViewer Members