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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; 
 
// 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 
 
' 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)

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

Help Version 19.0.2017.10.27

Leadtools.Controls.WinForms Assembly

Introduction

Getting Started

Namespaces

Leadtools.Controls Namespace

Assemblies