In This Topic ▼

BeginUpdate Method

Summary

Prevents the control from drawing until the EndUpdate method is called.

Syntax

C++/CLI

C++

public virtual void BeginUpdate()

public: 
virtual void BeginUpdate();

public:  
   virtual void BeginUpdate()

Remarks

When you want to disable repainting of the viewer, call BeginUpdate. When you are ready to resume painting call EndUpdate.

Example

This sample zooms out on the image, keeping it centered. The resulting transform is displayed in the console.

using Leadtools.WinForms; 
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Drawing; 
 
///  
// center the loaded image in the middle of rasterImageViewer if the image smaller than the viewer size  
private void centerImage(RasterImageViewer viewer) 
{ 
   // do center only when RasterViewerSizeMode == Normal 
   if (viewer.SizeMode == RasterPaintSizeMode.Normal) 
   { 
      if (viewer.IsImageAvailable == true) 
      { 
         if (viewer.Image != null) 
         { 
            int viewerWidth = viewer.Right - viewer.Left; 
            int viewerHeight = viewer.Bottom - viewer.Top; 
            int imageWidth = (int)(viewer.LogicalViewRectangle.Width * viewer.ScaleFactor); 
            int imageHeight = (int)(viewer.LogicalViewRectangle.Height * viewer.ScaleFactor); 
 
            if (imageWidth < viewerWidth) 
               viewer.BorderPadding.Left = (viewerWidth - imageWidth) / 2; 
            else 
               viewer.BorderPadding.Left = 0; 
 
            if (imageHeight < viewerHeight) 
               viewer.BorderPadding.Top = (viewerHeight - imageHeight) / 2; 
            else 
               viewer.BorderPadding.Top = 0; 
         } 
      } 
   } 
} 
 
private void viewer_TransformedChanged(object sender, EventArgs e) 
{ 
   RasterImageViewer viewer = sender as RasterImageViewer; 
   string s = string.Format("Transform: {0} {1} {2} {3} {4} {5}", 
      viewer.Transform.Elements[0], 
      viewer.Transform.Elements[1], 
      viewer.Transform.Elements[2], 
      viewer.Transform.Elements[3], 
      viewer.Transform.Elements[4], 
      viewer.Transform.Elements[5]); 
 
   Console.WriteLine(s); 
} 
 
public void RasterImageViewer_BeginUpdate(RasterImageViewer viewer) 
{ 
   viewer.TransformChanged += new EventHandler(viewer_TransformedChanged); 
 
   viewer.BeginUpdate();  // suspend painting of the image  
   viewer.ScaleFactor = viewer.ScaleFactor * 0.9F; 
   centerImage(viewer); 
   viewer.EndUpdate(); // start painting of the image  
 
   viewer.TransformChanged -= new EventHandler(viewer_TransformedChanged); 
}

Requirements

Target Platforms