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HitTestItem Method

Summary

First item that is under a physical (in viewer pixel) coordinates.

Syntax
C#
VB
C++
public virtual ImageViewerItem HitTestItem( 
   LeadPoint point 
) 
Public Overridable Function HitTestItem( 
   ByVal point As LeadPoint 
) As ImageViewerItem 
public:  
   virtual ImageViewerItem^ HitTestItem( 
      LeadPoint^ point 
   ) 

Parameters

point

The point in physical (in viewer pixel) coordinates.

Return Value

The first item that is under this point or null if no such item exists.

Remarks

HitTestItem method will return the item if any part of it is under the specified point. To further fine-tune the hit testing operation and obtain the specific item part, call HitTestItemPart passing the item obtained from HitTestItem and the desired part.

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

Example

This example will add a few items to the viewer and then perform hit-testing using the mouse showing the specific item part.

Run the demo, click the Example button and notice perform hit-testing.

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:

C#
VB
using Leadtools; 
using Leadtools.Controls; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using LeadtoolsExamples.Common; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
public void ImageViewerHitTestItem_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.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(ImagesPath.Path, 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); 
      } 
   } 
 
   string[] itemPartNames = 
      { 
         "View", 
         "Item", 
         "Content", 
         "Image", 
         "TextArea", 
         "Text", 
         "Floater" 
      }; 
 
   // Hook to the viewer mouse click event 
   _imageViewer.MouseClick += (sender, e) => 
   { 
      var point = LeadPoint.Create(e.X, e.Y); 
      // Hit-test the item 
      var item = _imageViewer.HitTestItem(point); 
      // If we have an item, find out the part 
      if (item != null) 
      { 
         var part = _imageViewer.HitTestItemPart(item, point); 
         _label.Text = string.Format("Clicked the {0} part of item at index {1}", 
            itemPartNames[(int)part], 
            _imageViewer.Items.IndexOf(item)); 
      } 
      else 
      { 
         _label.Text = "Click the view"; 
      } 
   }; 
} 
Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub ImageViewerHitTestItem_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.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 
 
   Dim itemPartNames As String() = {"View", "Item", "Content", "Image", "TextArea", "Text", "Floater"} 
 
   ' Hook to the viewer mouse click event 
   AddHandler _imageViewer.MouseClick, 
   Sub(sender, e) 
      Dim point As LeadPoint = LeadPoint.Create(e.X, e.Y) 
      ' Hit-test the item 
      Dim item As ImageViewerItem = _imageViewer.HitTestItem(point) 
      ' If we have an item, find out the part 
      If Not item Is Nothing Then 
         Dim part As ImageViewerItemPart = _imageViewer.HitTestItemPart(item, point) 
         _label.Text = String.Format("Clicked the {0} part of item at index {1}", itemPartNames(CInt(part)), _imageViewer.Items.IndexOf(item)) 
      Else 
         _label.Text = "Click the view" 
      End If 
   End Sub 
End Sub 

Requirements

Target Platforms

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