PostRender Event

Summary

Occurs after the view is rendered.

Syntax

C++

public event EventHandler<ImageViewerRenderEventArgs> PostRender

Public Event PostRender As EventHandler(Of Leadtools.Controls.ImageViewerRenderEventArgs)

public:  
   event EventHandler<Leadtools::Controls::ImageViewerRenderEventArgs^>^ PostRender

Remarks

For more information, refer to Image Viewer Rendering.

Example

This example will show how to customize the view rendering to draw extra shapes with and without transformation.

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 LeadtoolsExamples.Common; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
public void ImageViewerPostRender_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); 
      } 
   } 
 
   // Render on the view 
   _imageViewer.PostRender += (sender, e) => 
   { 
      // Rendering the whole view 
      var graphics = e.PaintEventArgs.Graphics; 
 
      // Blue ellipse at fixed position. This will stay the same and will not scroll or zoom 
      using (var brush = new SolidBrush(Color.FromArgb(128, Color.Blue))) 
         graphics.FillEllipse(brush, new Rectangle(0, 0, 100, 100)); 
 
      // Red ellipse at relative position, this will scroll and zoom with the view 
      var gstate = graphics.Save(); 
 
      var transform = _imageViewer.ViewTransform; 
      using (var matrix = new System.Drawing.Drawing2D.Matrix( 
         (float)transform.M11, (float)transform.M12, (float)transform.M21, (float)transform.M22, 
         (float)transform.OffsetX, (float)transform.OffsetY)) 
         graphics.MultiplyTransform(matrix); 
 
      graphics.FillEllipse(Brushes.Red, new Rectangle(0, 0, 100, 100)); 
 
      graphics.Restore(gstate); 
   }; 
 
   // Render on each item 
   _imageViewer.PostRenderItem += (sender, e) => 
   { 
      var item = e.Item; 
 
      var graphics = e.PaintEventArgs.Graphics; 
 
      var gstate = graphics.Save(); 
 
      // Get the bounding rectangle for the image 
      var bounds = LeadRectD.Create(0, 0, item.Image.ImageWidth, item.Image.ImageHeight); 
 
      // Add the image transform to the graphics 
      var transform = _imageViewer.GetItemImageTransform(item); 
      using (var matrix = new System.Drawing.Drawing2D.Matrix( 
         (float)transform.M11, (float)transform.M12, (float)transform.M21, (float)transform.M22, 
         (float)transform.OffsetX, (float)transform.OffsetY)) 
         graphics.MultiplyTransform(matrix); 
 
      // Red hilight on top of each item image 
      using (var brush = new SolidBrush(Color.FromArgb(128, Color.Red))) 
         graphics.FillRectangle(brush, (float)bounds.X, (float)bounds.Y, (float)bounds.Width, (float)bounds.Height); 
 
      graphics.Restore(gstate); 
   }; 
}

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub ImageViewerPostRender_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 
 
   ' Render on the view 
   AddHandler _imageViewer.PostRender, 
   Sub(sender, e) 
      ' Rendering the whole view 
      Dim graphics As Graphics = e.PaintEventArgs.Graphics 
 
      ' Blue ellipse at fixed position. This will stay the same and will not scroll or zoom 
      Using brush As New SolidBrush(Color.FromArgb(128, Color.Blue)) 
         graphics.FillEllipse(brush, New Rectangle(0, 0, 100, 100)) 
      End Using 
 
      ' Red ellipse at relative position, this will scroll and zoom with the view 
      Dim gstate As System.Drawing.Drawing2D.GraphicsState = graphics.Save() 
 
      Dim transform As LeadMatrix = _imageViewer.ViewTransform 
      Using matrix As New System.Drawing.Drawing2D.Matrix(CSng(transform.M11), CSng(transform.M12), CSng(transform.M21), 
                                                          CSng(transform.M22), CSng(transform.OffsetX), CSng(transform.OffsetY)) 
         graphics.MultiplyTransform(matrix) 
      End Using 
 
      graphics.FillEllipse(Brushes.Red, New Rectangle(0, 0, 100, 100)) 
 
      graphics.Restore(gstate) 
   End Sub 
 
   ' Render on each item 
   AddHandler _imageViewer.PostRenderItem, 
   Sub(sender, e) 
      Dim item As ImageViewerItem = e.Item 
 
      Dim graphics As Graphics = e.PaintEventArgs.Graphics 
 
      Dim gstate As System.Drawing.Drawing2D.GraphicsState = graphics.Save() 
 
      ' Get the bounding rectangle for the image 
      Dim bounds As LeadRectD = LeadRectD.Create(0, 0, item.Image.ImageWidth, item.Image.ImageHeight) 
 
      ' Add the image transform to the graphics 
      Dim transform As LeadMatrix = _imageViewer.GetItemImageTransform(item) 
      Using matrix As New System.Drawing.Drawing2D.Matrix(CSng(transform.M11), CSng(transform.M12), CSng(transform.M21), 
                                                          CSng(transform.M22), CSng(transform.OffsetX), CSng(transform.OffsetY)) 
         graphics.MultiplyTransform(matrix) 
      End Using 
 
      ' Red hilight on top of each item image 
      Using brush As New SolidBrush(Color.FromArgb(128, Color.Red)) 
         graphics.FillRectangle(brush, CSng(bounds.X), CSng(bounds.Y), CSng(bounds.Width), CSng(bounds.Height)) 
      End Using 
 
      graphics.Restore(gstate) 
   End Sub 
End Sub

Event Data

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

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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Help Version 20.0.2020.4.3

Leadtools.Controls Assembly

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Leadtools.Controls Namespace

Assemblies