ActiveItem Property

Summary

Active item of this image viewer.

Syntax

C++

public virtual ImageViewerItem ActiveItem { get; set; }

Public Overridable Property ActiveItem() As ImageViewerItem 
   Get 
   Set

public:  
   virtual property ImageViewerItem^ ActiveItem 
   { 
      ImageViewerItem^ get() 
      void set(ImageViewerItem^ value) 
   }

Property Value

The active item of this image viewer. This value cannot be null.

Remarks

For more information, refer to Image Viewer Items.

Example

This example will use the viewer as a single-selection enabled list of images and shows how to track the current active item.

Start with the ImageViewer example, remove all the code inside the example function (search for the "// TODO: add example code here" comment), and insert the following code:

using Leadtools; 
using Leadtools.Controls; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using LeadtoolsExamples.Common; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
public void ActiveItem_Example() 
{ 
 
   // Clear all the images already the viewer 
   _imageViewer.Items.Clear(); 
   // Use vertical view layout 
   _imageViewer.ViewLayout = new ImageViewerVerticalViewLayout(); 
   // Make sure the item size is larger than the image size (thumbnails mode) 
   _imageViewer.ItemSize = LeadSize.Create(200, 200); 
   _imageViewer.ImageBorderThickness = 1; 
   // Change the active item background color 
   _imageViewer.ActiveItemBackgroundColor = Color.LightBlue; 
   _imageViewer.SelectedItemBackgroundColor = Color.LightBlue; 
 
   // Add 4 items to the viewer 
   using (var codecs = new RasterCodecs()) 
   { 
      for (var page = 1; page <= 4; page++) 
      { 
         var item = new ImageViewerItem(); 
         var fileName = Path.Combine(ImagesPath.Path, string.Format("ocr{0}.tif", page)); 
 
         // Create a thumbnail from the image 
         using (var image = codecs.Load(fileName, page)) 
         { 
            item.Image = image.CreateThumbnail(180, 180, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample); 
         } 
         _imageViewer.Items.Add(item); 
      } 
   } 
 
   // Add the interface mode to select items (single) 
   var selectItemsMode = new ImageViewerSelectItemsInteractiveMode(); 
   selectItemsMode.SelectionMode = ImageViewerSelectionMode.Single; 
   // Tell the mode to set the active item for us 
   selectItemsMode.AutoItemMode = ImageViewerAutoItemMode.AutoSetActive; 
   _imageViewer.DefaultInteractiveMode = selectItemsMode; 
 
   // Hook to the ActiveItemChanged event and update the label 
   _imageViewer.ActiveItemChanged += (sender, e) => 
   { 
      var index = _imageViewer.Items.IndexOf(_imageViewer.ActiveItem); 
      _label.Text = "ActiveIndex index is " + index.ToString(); 
   }; 
 
}

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub ActiveItem_Example() 
   ' Clear all the images already the viewer 
   _imageViewer.Items.Clear() 
   ' Use vertical view layout 
   _imageViewer.ViewLayout = New ImageViewerVerticalViewLayout() 
   ' Make sure the item size is larger than the image size (thumbnails mode) 
   _imageViewer.ItemSize = LeadSize.Create(200, 200) 
   _imageViewer.ImageBorderThickness = 1 
   ' Change the active item background color 
   _imageViewer.ActiveItemBackgroundColor = Color.LightBlue 
   _imageViewer.SelectedItemBackgroundColor = Color.LightBlue 
 
   ' Add 4 items to the viewer 
   Using codecs As New RasterCodecs() 
      For page As Integer = 1 To 4 
         Dim item As New ImageViewerItem() 
         Dim fileName As String = Path.Combine(ImagesPath.Path, String.Format("ocr{0}.tif", page)) 
 
         ' Create a thumbnail from the image 
         Using image As RasterImage = codecs.Load(fileName, page) 
            item.Image = image.CreateThumbnail(180, 180, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample) 
         End Using 
         _imageViewer.Items.Add(item) 
      Next page 
   End Using 
 
   ' Add the interface mode to select items (single) 
   Dim selectItemsMode As New ImageViewerSelectItemsInteractiveMode() 
   selectItemsMode.SelectionMode = ImageViewerSelectionMode.Single 
   ' Tell the mode to set the active item for us 
   selectItemsMode.AutoItemMode = ImageViewerAutoItemMode.AutoSetActive 
   _imageViewer.DefaultInteractiveMode = selectItemsMode 
 
   ' Hook to the ActiveItemChanged event and update the label 
   AddHandler _imageViewer.ActiveItemChanged, 
   Sub(sender, e) 
      Dim index As Integer = _imageViewer.Items.IndexOf(_imageViewer.ActiveItem) 
      _label.Text = "ActiveIndex index is " & index.ToString() 
   End Sub 
End Sub

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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Help Version 20.0.2020.4.3

Leadtools.Controls Assembly

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