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ActiveItem Property (ImageViewer)

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; 
 
// 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 
 
' 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()