RenderRedirect Method

Render the content of the viewer to an external context.

Syntax

C#
Visual Basic
Objective-C
Java

public virtual void RenderRedirect( 
   Graphics graphics,
   ImageViewerRenderRedirectOptions options,
   LeadRect clipRectangle
)

'Declaration

Public Overridable Sub RenderRedirect( _
   ByVal graphics As Graphics, _
   ByVal options As ImageViewerRenderRedirectOptions, _
   ByVal clipRectangle As LeadRect _
)

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 targetting 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#
Visual Basic
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.Controls
Imports Leadtools.Codecs
Imports Leadtools.Drawing
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color

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()

using Leadtools;
using Leadtools.Controls;
using Leadtools.Codecs;
using Leadtools.Drawing;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;

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();
};

Requirements

Target Platforms

Reference

ImageViewer Class
ImageViewer Members