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ActiveItem Property


Active item of this image viewer.

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

Property Value

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


For more information, refer to Image Viewer Items.


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 Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
public ImageViewerForm _form = new ImageViewerForm(); 
public ImageViewer _imageViewer; 
public void ImageViewerActiveItemExample() 
   // Get the Form's ImageViewer control 
   _imageViewer = _form.ImageViewer; 
   // Clear all the images already the viewer 
   // 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(LEAD_VARS.ImagesDir, 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); 
   // 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 
   _imageViewer.ActiveItemChanged += (sender, e) => 
      var index = _imageViewer.Items.IndexOf(_imageViewer.ActiveItem); 
      Debug.WriteLine("ActiveIndex index is " + index.ToString()); 
static class LEAD_VARS 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 

Target Platforms

Help Version 23.0.2024.2.29
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Leadtools.Controls Assembly

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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.