GetFirstVisibleItem Method

Summary

First visible item or part of it in the viewer.

Syntax

C++/CLI

public virtual ImageViewerItem GetFirstVisibleItem( 
   ImageViewerItemPart part 
)

public:  
   virtual ImageViewerItem^ GetFirstVisibleItem( 
      ImageViewerItemPart^ part 
   )

Parameters

part

The item part requested. To use the whole item, pass ImageViewerItemPart.View.

Return Value

The first visible item or null if the item does not have any visible items.

Remarks

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 ImageViewer _imageViewer; 
 
public void ImageViewerTransformChangedExample() 
{ 
   // Get the ImageViewer control from the Form 
   _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.ItemBorderThickness = 1; 
   _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(380, 380, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample); 
         } 
 
         item.Text = string.Format("Item {0}", page - 1); 
         _imageViewer.Items.Add(item); 
      } 
   } 
 
   // Hook to the TransformChanged event that shows occur whenever we pan or zoom 
   _imageViewer.TransformChanged += (sender, e) => 
   { 
      // Get the GetFirstVisibleItem and largest 
      var firstVisible = _imageViewer.GetFirstVisibleItem(ImageViewerItemPart.Item); 
      var largest = _imageViewer.GetLargestVisibleItem(ImageViewerItemPart.Item); 
 
      // Show both in Debug Console 
      Debug.WriteLine(string.Format("First visible {0} - Largest {1}", 
         firstVisible != null ? firstVisible.Text : "none", 
         largest != null ? largest.Text : "none")); 
   }; 
} 
 
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

Leadtools.Controls Assembly

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