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RenderItemRegion Event

Summary

Renders the item region.

Syntax
C#
C++/CLI
public event EventHandler<ImageViewerRenderEventArgs> RenderItemRegion 
public:  
   event EventHandler<Leadtools::Controls::ImageViewerRenderEventArgs^>^ RenderItemRegion 
Remarks

During this part of the rendering cycle, the viewer will check if the image of this item contains a valid region. If this is true and the value of ImageRegionRenderMode is other than ControlRegionRenderMode.None then the viewer will render the outline of the region on top of the image.

For more information, refer to Image Viewer Rendering.

Example
C#
using Leadtools; 
using Leadtools.Controls; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
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(LEAD_VARS.ImagesDir, 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); 
   }; 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS22\Resources\Images"; 
} 
Event Data
ParameterTypeDescription
senderobjectThe source of the event.
eImageViewerRenderEventArgsThe event data.
Requirements

Target Platforms

Help Version 22.0.2023.1.24
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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.

Leadtools.Controls Assembly
Products | Support | Contact Us | Intellectual Property Notices
© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.