←Select platform

CenterAtPoint Method

Summary

Centers the image display at the specified point.

Syntax

C++

public virtual void CenterAtPoint( 
   Point pt 
)

  
Public Overridable Sub CenterAtPoint( _ 
   ByVal pt As Point _ 
)

public: 
virtual void CenterAtPoint(  
   Point pt 
)

Parameters

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

Remarks

The control will position the scrollbars according to user cursor moves, therefore, this method is only functional if the control has visible scrollbars (SizeMode is SizeMode.Normal or SizeMode.FitWidth and the view port is less than the image size).

The control will call this method during InteractiveMode.Pan.

Example

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

Silverlight C#

Silverlight VB

using Leadtools.Help; 
using Leadtools.Windows.Controls; 
 
void ZoomAndCenter(ImageViewer 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.ActualWidth, viewer.ActualHeight), new Rect(viewer.PhysicalSize)); 
 
      // Get the center of what you see in physical coordinates 
      Point center = new Point(rc.Left + rc.Width / 2 * scaleFactor, rc.Top + rc.Height / 2 * scaleFactor); 
 
      // Set the new scale factor 
      viewer.ScaleFactor = scaleFactor; 
 
      // Bring the old center into the center of the view 
      viewer.CenterAtPoint(center); 
   } 
}

Imports Leadtools.Windows.Controls 
 
Private Sub ZoomAndCenter(ByVal viewer As ImageViewer, 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.ActualWidth, viewer.ActualHeight), New Rect(viewer.PhysicalSize)) 
 
      ' Get the center of what you see in physical coordinates 
      Dim center As Point = New Point(rc.Left + rc.Width / 2 * scaleFactor, rc.Top + rc.Height / 2 * scaleFactor) 
 
      ' 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

using Leadtools.Help; 
using Leadtools.Windows.Controls; 
 
void ZoomAndCenter(ImageViewer 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 
      LeadRect rc = LeadRect.Intersect(new LeadRect(0, 0, (int)viewer.ActualWidth, (int)viewer.ActualHeight), new LeadRect(0, 0, (int)viewer.PhysicalSize.Width, (int)viewer.PhysicalSize.Height)); 
 
      // Get the center of what you see in physical coordinates 
      Point center = new Point(rc.Left + rc.Width / 2 * scaleFactor, rc.Top + rc.Height / 2 * scaleFactor); 
 
      // Set the new scale factor 
      viewer.ScaleFactor = scaleFactor; 
 
      // Bring the old center into the center of the view 
      viewer.CenterAtPoint(center); 
   } 
}

Imports Leadtools 
Imports Leadtools.Windows.Controls 
 
Private Sub ZoomAndCenter(ByVal viewer As ImageViewer, 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 LeadRect = LeadRect.Intersect(New LeadRect(0, 0, CInt(viewer.ActualWidth), CInt(viewer.ActualHeight)), New LeadRect(0, 0, CInt(viewer.PhysicalSize.Width), CInt(viewer.PhysicalSize.Height))) 
 
      ' Get the center of what you see in physical coordinates 
      Dim center As Point = New Point(rc.Left + rc.Width / 2 * scaleFactor, rc.Top + rc.Height / 2 * scaleFactor) 
 
      ' 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

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Help Version 19.0.2017.10.27

Leadtools.Windows.Controls Assembly

Introduction

Getting Started

Namespaces

Leadtools.Windows.Controls Namespace

Assemblies