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CenterAtPoint Method
See Also  Example
Leadtools.Windows.Controls Namespace > BitmapSourceViewer Class : CenterAtPoint Method



pt
The point at which to center the image display, in client coordinates.
Centers the image display at the specified point.

Syntax

Visual Basic (Declaration) 
Public Overridable Sub CenterAtPoint( _
   ByVal pt As Point _
) 
Visual Basic (Usage)Copy Code
Dim instance As BitmapSourceViewer
Dim pt As Point
 
instance.CenterAtPoint(pt)
C# 
public virtual void CenterAtPoint( 
   Point pt
)
C++/CLI 
public:
virtual void CenterAtPoint( 
   Point pt
) 

Parameters

pt
The point at which to center the image display, in client coordinates.

Example

This example shows a method to change the viewer scale factor (zoom) while keeping the viewer centered.

Visual BasicCopy Code
Private Sub ZoomAndCenter(ByVal viewer As BitmapSourceViewer, ByVal scaleFactor As Double)
    ' Minimum and maximum scale factors allowed (change if you have to)
    Const minimumScaleFactor As Double = 0.05
    Const maximumScaleFactor As Double = 11
    ' Normalize the scale factor based on min and max
    scaleFactor = Math.Max(minimumScaleFactor, Math.Min(maximumScaleFactor, scaleFactor))

    ' Check if we need to change the scale factor for the viewer
    If viewer.ScaleFactor <> scaleFactor Then
        ' Get the current center in logical units
        ' We will use this point later to re-center the viewer

        ' Get what you see in physical coordinates
        Dim rc As Rect = Rect.Intersect(New Rect(0, 0, viewer.Width, viewer.Height), viewer.PhysicalViewRectangle)

        ' Get the center of what you see in physical coordinates
        Dim center As System.Windows.Point = New System.Windows.Point(rc.Left + rc.Width / 2, rc.Top + rc.Height / 2)

        ' Set the new scale factor
        viewer.ScaleFactor = scaleFactor

        ' Bring the old center into the center of the view
        viewer.CenterAtPoint(center)
    End If
End Sub
C#Copy Code
void ZoomAndCenter(BitmapSourceViewer viewer, double scaleFactor) 

   // Minimum and maximum scale factors allowed (change if you have to) 
   const double minimumScaleFactor = 0.05; 
   const double maximumScaleFactor = 11; 
   // Normalize the scale factor based on min and max 
   scaleFactor = Math.Max(minimumScaleFactor, Math.Min(maximumScaleFactor, scaleFactor)); 
 
   // Check if we need to change the scale factor for the viewer 
   if(viewer.ScaleFactor != scaleFactor) 
   { 
      // Get the current center in logical units 
      // We will use this point later to re-center the viewer 
 
      // Get what you see in physical coordinates 
      Rect rc = Rect.Intersect(new Rect(0, 0, viewer.Width, viewer.Height), viewer.PhysicalViewRectangle); 
 
      // Get the center of what you see in physical coordinates 
      Point center = new Point(rc.Left + rc.Width / 2, rc.Top + rc.Height / 2); 
 
      // Set the new scale factor 
      viewer.ScaleFactor = scaleFactor; 
 
      // Bring the old center into the center of the view 
      viewer.CenterAtPoint(center); 
   } 
}

Requirements

Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Vista, and Windows Server 2003 family

See Also