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AutoDisposeImages Property

Summary

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

Syntax

C++

public virtual bool AutoDisposeImages { get; set; }

Public Overridable Property AutoDisposeImages As Boolean

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

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

This sample loads two images to demonstrate how the AutoDisposeImages property effects whether the item image remains usable.

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"; 
}

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

Requirements

Target Platforms

Reference

RasterImageViewer Class

RasterImageViewer Members

Help Version 19.0.2017.10.27

Leadtools.WinForms Assembly

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