ItemChanged Event

Summary

Occurs when any of the items inside this ImageViewer changes.

Syntax

C++/CLI

public event EventHandler<ImageViewerItemChangedEventArgs> ItemChanged

public: 
   event EventHandler<Leadtools::Controls::ImageViewerItemChangedEventArgs^>^ ItemChanged

Remarks

This event occurs when any of the items inside this ImageViewer changes. The ImageViewerItemChangedEventArgs will contain the item that has been changed in ImageViewerItemChangedEventArgs.Item and the reason for the change in ImageViewerItemChangedEventArgs.Reason.

Change the value of the following properties or calling the methods programmatically or by the viewer will raise the ItemChanged event with the specified reason:

Property or Method	Value of ImageViewerItemChangedEventArgs.Reason
Image	ImageViewerItemChangedReason.Image (and optionally ImageViewerItemChangedReason is automatically changed by the viewer.)
SvgDocument	ImageViewerItemChangedReason.Image (and optionally ImageViewerItemChangedReason is automatically changed by the viewer.)
Url	ImageViewerItemChangedReason.Image (and optionally ImageViewerItemChangedReason is automatically changed by the viewer.)
ImageSize	ImageViewerItemChangedReason.Image
PageNumber	ImageViewerItemChangedReason.Image (and optionally ImageViewerItemChangedReason is automatically changed by the viewer.)
Size	ImageViewerItemChangedReason.Size
Resolution	ImageViewerItemChangedReason.Resolution
BackImage	ImageViewerItemChangedReason.BackImage
BackImageUrl	ImageViewerItemChangedReason.BackImageUrl
Floater	ImageViewerItemChangedReason.Floater
FloaterTransform	ImageViewerItemChangedReason.FloaterTransform
FloaterOpacity	ImageViewerItemChangedReason.FloaterTransform
Text	ImageViewerItemChangedReason.Text
IsSelected	ImageViewerItemChangedReason.Selected
IsHovered	ImageViewerItemChangedReason.Hovered
IsEnabled	ImageViewerItemChangedReason.Transform
IsVisible	ImageViewerItemChangedReason.Transform
Transform	ImageViewerItemChangedReason.Transform
Zoom	ImageViewerItemChangedReason.Transform
ResizeOnTransform	ImageViewerItemChangedReason.Transform
ClipImageToContent	ImageViewerItemChangedReason.Transform
ImageHorizontalAlignment	ImageViewerItemChangedReason.Transform
ImageVerticalAlignment	ImageViewerItemChangedReason.Transform
TextHorizontalAlignment	ImageViewerItemChangedReason.Transform
TextHorizontalAlignment	ImageViewerItemChangedReason.Transform

The viewer automatically listens to these events internally and will perform the necessary action, for example, if any property that affect the transformation changes, UpdateTransform will be called. If the property change requires rendering only, then the item will be invalidated.

Example

This example will track the ItemChanged and ItemError event and show information on them.

Run the demo, click the Example button.

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 ImageViewerItemChangedExample() 
{ 
   // Get the Form's ImageViewer control 
   _imageViewer = _form.ImageViewer; 
 
   // ImageViewerItemChangedEventArgs reference 
   _imageViewer.ItemChanged += (sender, e) => 
   { 
      var item = e.Item; 
      var sb = new StringBuilder(); 
      sb.AppendFormat("ItemChanged:{0} Reason:{1} Size:{2} Res:{3}", _imageViewer.Items.IndexOf(item), e.Reason, item.Size, item.Resolution); 
      if (item.Image != null) 
         sb.AppendFormat(" Image: {0} bpp {1} by {2}", item.Image.BitsPerPixel, item.Image.Width, item.Image.Height); 
      else 
         sb.AppendFormat(" Image: null"); 
      Debug.WriteLine(sb.ToString()); 
 
      if (item.Url != null) 
         Debug.WriteLine("  Url:" + item.Url.ToString()); 
   }; 
 
   // ImageViewerItemErrorEventArgs reference 
   _imageViewer.ItemError += (sender, e) => 
   { 
      e.RemoveEmptyItem = false; 
      Debug.WriteLine("Data: {0}, Error: {1}", e.Data, e.Error); 
   }; 
 
   // Load an image 
   using (var codecs = new RasterCodecs()) 
      _imageViewer.Image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif")); 
 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
}

Event Data

Parameter	Type	Description
sender	object	The source of the event.
e	ImageViewerItemChangedEventArgs	The event data.

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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Help Version 23.0.2024.2.29