TransformChanged Event

Summary

Occurs when the transformation matrix of the view or any of the item changes.

Syntax

C++

public event EventHandler TransformChanged

Public Event TransformChanged As EventHandler

public:  
   event EventHandler^ TransformChanged

Remarks

This event is raised when the transformation matrix of the view or any of the item changes by either a programmatic modification or end-user interaction through the user interface.

The event is raised by the UpdateTransform method after all the calculations needed is performed, it gives the user a chance for a catch all notification when anything in the viewer changes.

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

Example

This example will hook to the TransformChanged event of the viewer and track the current first and largest visible items.

Run the demo, click the Example button and notice that as you pan and zoom the viewer, the values are displayed in the label.

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 void TransformChanged_Example() 
{ 
   // 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.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(180, 180, 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 the label 
      _label.Text = 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:\LEADTOOLS21\Resources\Images"; 
}

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub TransformChanged_Example() 
   ' 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.ItemPadding = New Padding(8, 8, 8, 20) 
   _imageViewer.ItemBorderThickness = 1 
   _imageViewer.ImageBorderThickness = 1 
 
   ' 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 
 
         item.Text = String.Format("Item {0}", page - 1) 
         _imageViewer.Items.Add(item) 
      Next page 
   End Using 
 
   ' Hook to the TransformChanged event that shows occur whenever we pan or zoom 
   AddHandler _imageViewer.TransformChanged, 
   Sub(sender, e) 
      ' Get the GetFirstVisibleItem and largest 
      Dim firstVisible As ImageViewerItem = _imageViewer.GetFirstVisibleItem(ImageViewerItemPart.Item) 
      Dim largest As ImageViewerItem = _imageViewer.GetLargestVisibleItem(ImageViewerItemPart.Item) 
 
      ' Show both in the label 
      If Not firstVisible Is Nothing Then 
         If Not largest Is Nothing Then 
            _label.Text = String.Format("First visible {0} - Largest {1}", firstVisible.Text, largest.Text) 
         Else 
            _label.Text = String.Format("First visible {0} - Largest {1}", firstVisible.Text, "none") 
         End If 
      Else 
         If Not largest Is Nothing Then 
            _label.Text = String.Format("First visible {0} - Largest {1}", "none", largest.Text) 
         Else 
            _label.Text = String.Format("First visible {0} - Largest {1}", "none", "none") 
         End If 
      End If 
   End Sub 
End Sub

Event Data

Parameter	Type	Description
sender	object	The source of the event.

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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