ActiveItem Property

Summary

Active item of this image viewer.

Syntax

C++/CLI

public virtual ImageViewerItem ActiveItem { 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 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 
   _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(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); 
         } 
         _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 
   _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"; 
}

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

Download our FREE evaluation

Help Version 23.0.2024.2.29

Leadtools.Controls Assembly

Introduction

Getting Started

Namespaces

Leadtools.Controls Namespace

Assemblies