EnsureItemVisibleByIndex Method

Summary

Ensures that the item at the specified index is visible in the viewer.

Syntax

C++/CLI

public virtual void EnsureItemVisibleByIndex( 
   int index 
)

public:  
   virtual void EnsureItemVisibleByIndex( 
      int index 
   )

Parameters

index

0-based index of the item

Remarks

To go to an item, use GotoItem, to go to an item by its index, use GotoItemByIndex.

The "GoTo" methods scrolls the viewer so the top-left portion of the item is visible in the current control boundary without changing the other transformation properties.

To ensure that an item is visible, use EnsureItemVisible, to ensure an item is visible giving its index, use EnsureItemVisibleByIndex.

The "Ensure" methods scrolls the viewer the minimum required to ensure the item is fully visible in the current control boundary without changing the other transformation property. If the item is already fully visible, then nothing happens. If the item is larger than the current control boundary, then the viewer will scrolls the minimum amount required where any of the edges (top-left, top-right, bottom-left or bottom-right) is visible.

For more information refer to Image Viewer Layouts, Image Viewer Appearance, Image Viewer Items, Image Viewer Transformation, and Image Viewer Bounds and Transform.

Example

using Leadtools; 
using Leadtools.Controls; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
 
public ImageViewerForm _form = new ImageViewerForm(); 
public ComboBox comboBox = new ComboBox(); 
public ImageViewer _imageViewer; 
 
public void ImageViewerGotoItemByIndexExample() 
{ 
 
   // 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(400, 400); 
   _imageViewer.ItemPadding = new Padding(8, 8, 8, 20); 
   _imageViewer.ImageBorderThickness = 1; 
 
   // 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(400, 400, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample); 
         } 
 
         item.Text = string.Format("Item {0}", page - 1); 
         _imageViewer.Items.Add(item); 
         _imageViewer.EnsureItemVisible(item); 
         _imageViewer.EnsureItemVisibleByIndex(page - 1); 
         _imageViewer.GotoItem(item); 
      } 
   } 
 
   // Add a combo box control to show the items 
   comboBox.Top = _form.ClientRectangle.Top; 
   _form.Controls.Add(comboBox); 
 
   // Add an entry for each item to the combo box 
   foreach (var item in _imageViewer.Items) 
      comboBox.Items.Add(item.Text); 
 
   comboBox.BringToFront(); 
 
   // When the user selects an item from the combo box ... 
   comboBox.SelectedIndexChanged += ComboBox_SelectedIndexChanged; 
} 
 
private void ComboBox_SelectedIndexChanged(object sender, EventArgs e) 
{ 
   // Get the corresponding item index... 
   var index = comboBox.SelectedIndex; 
   // And go to it 
   _imageViewer.GotoItemByIndex(index); 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
}

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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Help Version 23.0.2024.2.29