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RenderRedirect Method

Summary

Render the content of the viewer to an external context.

Syntax
C#
VB
C++
public virtual void RenderRedirect( 
   Graphics graphics, 
   ImageViewerRenderRedirectOptions options, 
   LeadRect clipRectangle 
) 
Public Overridable Sub RenderRedirect( 
   ByVal graphics As System.Drawing.Graphics, 
   ByVal options As ImageViewerRenderRedirectOptions, 
   ByVal clipRectangle As LeadRect 
) 
public:  
   virtual void RenderRedirect( 
      System::Drawing::Graphics^ graphics, 
      ImageViewerRenderRedirectOptions^ options, 
      LeadRect^ clipRectangle 
   ) 

Parameters

graphics

Target device context to render the content of the viewer to.

options

Rendering options

clipRectangle

Clipping rectangle to use.

Remarks

This method can be used to render the content of the viewer to an external context. ImageViewerPanControl uses this method to show a smaller version of the viewer in a separate external control.

To take a "snapshot" of the viewer surface to perform such operations as screen capture or printing, use RenderRedirect passing it the target context (of the printer or a bitmap).

To perform live updates for operations such as pan window, subscribe to the RedirectRender event to get notified whenever the viewer content is changed. Then call RenderRedirect to render the content of the viewer into the target device.

During the render cycle, the value of IsRenderRedirected will be set to true if this particular rendering operation is targeting an external device other than the viewer itself. If you are performing custom rendering, you can check the value of this property to apply any modification needed.

Example

This example will mirror the content of the viewer into an external control with live updates whenever the viewer content changes.

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 TestRedirectRender() 
{ 
   PictureBox control = new PictureBox(); 
   control.Width = 400; 
   control.Dock = DockStyle.Right; 
   control.BringToFront(); 
   _imageViewer.BringToFront(); 
 
   bool renderView = false; 
 
   control.DoubleClick += (sender, e) => 
   { 
      renderView = !renderView; 
      control.Invalidate(); 
   }; 
 
   control.Paint += (sender, e) => 
   { 
      Graphics graphics = e.Graphics; 
 
      int delta = 20; 
      LeadRect destRect = LeadRect.Create(delta, delta, control.ClientSize.Width - delta * 2, control.ClientSize.Height - delta * 2); 
      LeadRect clipRect = destRect; 
 
      ImageViewerRenderRedirectOptions options = new ImageViewerRenderRedirectOptions(); 
 
      ImageViewerItem item = null; 
      if (!renderView) 
         item = _imageViewer.Items[0]; 
 
      LeadRectD sourceRect; 
 
      if (item == null) 
         sourceRect = _imageViewer.GetViewBounds(true, false); 
      else 
      { 
         sourceRect = _imageViewer.GetItemViewBounds(item, ImageViewerItemPart.Image, false); 
         options.RenderBackgrounds = false; 
         options.RenderBorders = false; 
         options.RenderItemStates = false; 
         options.RenderShadows = false; 
         options.RenderText = false; 
      } 
 
      options.CreateTransform(_imageViewer, destRect, sourceRect, ControlSizeMode.FitAlways, ControlAlignment.Center, ControlAlignment.Center); 
      clipRect = options.Transform.TransformRect(sourceRect).ToLeadRect(); 
 
      _imageViewer.RenderRedirect(graphics, options, clipRect); 
 
      graphics.DrawRectangle(Pens.Black, destRect.X, destRect.Y, destRect.Width + 1, destRect.Height + 1); 
 
      // Now lets find out how much of the view is visible (something pan window would do) 
      LeadRectD rect; 
      if (item == null) 
         rect = _imageViewer.GetViewBounds(true, true); 
      else 
         rect = _imageViewer.GetItemViewBounds(item, ImageViewerItemPart.Image, true); 
 
      LeadPointD[] points = 
      { 
         LeadPointD.Create(rect.Left, rect.Top), 
         LeadPointD.Create(rect.Right, rect.Bottom) 
      }; 
 
      options.Transform.TransformPoints(points); 
 
      double xmin = points[0].X; 
      double ymin = points[0].Y; 
      double xmax = xmin; 
      double ymax = ymin; 
 
      for (int i = 1; i < points.Length; i++) 
      { 
         if (points[i].X < xmin) xmin = points[i].X; 
         if (points[i].X > xmax) xmax = points[i].X; 
         if (points[i].Y < ymin) ymin = points[i].Y; 
         if (points[i].Y > ymax) ymax = points[i].Y; 
      } 
 
      LeadRectD bounds = LeadRectD.FromLTRB(xmin, ymin, xmax, ymax); 
      RectangleF rc = new RectangleF((float)bounds.X, (float)bounds.Y, (float)bounds.Width, (float)bounds.Height); 
      graphics.DrawRectangle(Pens.Yellow, rc.X, rc.Y, rc.Width - 1, rc.Height - 1); 
   }; 
 
   _imageViewer.RedirectRender += (sender, e) => 
   { 
      control.Invalidate(); 
   }; 
} 
Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub TestRedirectRender() 
   Dim control As PictureBox = New PictureBox() 
   control.Width = 400 
   control.Dock = DockStyle.Right 
   control.BringToFront() 
   _imageViewer.BringToFront() 
 
   Dim renderView As Boolean = False 
 
   AddHandler control.DoubleClick, 
   Sub(sender, e) 
      renderView = Not renderView 
      control.Invalidate() 
   End Sub 
 
   AddHandler control.Paint, 
   Sub(sender, e) 
      Dim graphics As Graphics = e.Graphics 
 
      Dim delta As Integer = 20 
      Dim destRect As LeadRect = LeadRect.Create(delta, delta, control.ClientSize.Width - delta * 2, control.ClientSize.Height - delta * 2) 
      Dim clipRect As LeadRect = destRect 
 
      Dim options As ImageViewerRenderRedirectOptions = New ImageViewerRenderRedirectOptions() 
 
      Dim item As ImageViewerItem = Nothing 
      If (Not renderView) Then 
         item = _imageViewer.Items(0) 
      End If 
 
      Dim sourceRect As LeadRectD 
 
      If item Is Nothing Then 
         sourceRect = _imageViewer.GetViewBounds(True, False) 
      Else 
         sourceRect = _imageViewer.GetItemViewBounds(item, ImageViewerItemPart.Image, False) 
         options.RenderBackgrounds = False 
         options.RenderBorders = False 
         options.RenderItemStates = False 
         options.RenderShadows = False 
         options.RenderText = False 
      End If 
 
      options.CreateTransform(_imageViewer, destRect, sourceRect, ControlSizeMode.FitAlways, ControlAlignment.Center, ControlAlignment.Center) 
      clipRect = options.Transform.TransformRect(sourceRect).ToLeadRect() 
 
      _imageViewer.RenderRedirect(graphics, options, clipRect) 
 
      graphics.DrawRectangle(Pens.Black, destRect.X, destRect.Y, destRect.Width + 1, destRect.Height + 1) 
 
      ' Now lets find out how much of the view is visible (something pan window would do) 
      Dim rect As LeadRectD 
      If item Is Nothing Then 
         rect = _imageViewer.GetViewBounds(True, True) 
      Else 
         rect = _imageViewer.GetItemViewBounds(item, ImageViewerItemPart.Image, True) 
      End If 
 
      Dim points As LeadPointD() = {LeadPointD.Create(rect.Left, rect.Top), LeadPointD.Create(rect.Right, rect.Bottom)} 
 
      options.Transform.TransformPoints(points) 
 
      Dim xmin As Double = points(0).X 
      Dim ymin As Double = points(0).Y 
      Dim xmax As Double = xmin 
      Dim ymax As Double = ymin 
 
      Dim i As Integer = 1 
      Do While i < points.Length 
         If points(i).X < xmin Then 
            xmin = points(i).X 
         End If 
         If points(i).X > xmax Then 
            xmax = points(i).X 
         End If 
         If points(i).Y < ymin Then 
            ymin = points(i).Y 
         End If 
         If points(i).Y > ymax Then 
            ymax = points(i).Y 
         End If 
         i += 1 
      Loop 
 
      Dim bounds As LeadRectD = LeadRectD.FromLTRB(xmin, ymin, xmax, ymax) 
      Dim rc As RectangleF = New RectangleF(CSng(bounds.X), CSng(bounds.Y), CSng(bounds.Width), CSng(bounds.Height)) 
      graphics.DrawRectangle(Pens.Yellow, rc.X, rc.Y, rc.Width - 1, rc.Height - 1) 
   End Sub 
 
   AddHandler _imageViewer.RedirectRender, Sub(sender, e) control.Invalidate() 
End Sub 

Requirements

Target Platforms

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Leadtools.Controls Assembly