Zoom Method

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
 
Public Sub ImageViewerZoom_Example() 
   ' Create the form that holds the ImageViewer 
   CType(New MyForm2(), MyForm2).ShowDialog() 
End Sub 
 
Private Class MyForm2 : Inherits Form 
   Public Sub New() 
      Me.Size = New Size(800, 800) 
   End Sub 
 
   ' LEADTOOLS ImageViewer to be used with this example 
   Private _imageViewer As ImageViewer 
   ' Ratio to use when the user zooms in or out. Change this if another value is needed, 
   ' for example, 2.0 will zoom the viewer in by 200% and out by 50% each time 
   Private Const _zoomRatio As Double = 1.2 
 
   Protected Overrides Sub OnLoad(ByVal e As EventArgs) 
      ' Create a panel to the top 
      Dim panel As New Panel() 
      panel.Dock = DockStyle.Top 
      panel.BorderStyle = BorderStyle.FixedSingle 
      Me.Controls.Add(panel) 
 
      ' Add a combo box for the zoom values 
      Dim zoomComboBox As New ComboBox() 
      zoomComboBox.Name = "zoomComboBox" 
      zoomComboBox.Location = New Point(8, 8) 
      zoomComboBox.DropDownStyle = ComboBoxStyle.DropDown 
 
      ' Add default zoom values 
      zoomComboBox.Items.AddRange(New String() {"10%", "25%", "50%", "75%", "100%", "125%", 
                                                "200%", "400%", "800%", "1600%", "2400%", 
                                                "3200%", "6400%", "Actual Size", "Fit Page", "Fit Width", "Fit Height"}) 
      panel.Controls.Add(zoomComboBox) 
 
      ' Add zoom in and out buttons 
      Dim zoomInButton As New Button() 
      zoomInButton.Text = "+" 
      zoomInButton.Location = New Point(zoomComboBox.Right + 8, zoomComboBox.Top - 1) 
      panel.Controls.Add(zoomInButton) 
      Dim zoomOutButton As New Button() 
      zoomOutButton.Text = "-" 
      zoomOutButton.Location = New Point(zoomInButton.Right + 2, zoomComboBox.Top - 1) 
      panel.Controls.Add(zoomOutButton) 
 
      ' Create the image viewer taking the rest of the form 
      _imageViewer = New ImageViewer() 
      _imageViewer.Dock = DockStyle.Fill 
      _imageViewer.ViewBorderThickness = 1 
      Me.Controls.Add(_imageViewer) 
      _imageViewer.BringToFront() 
 
      ' Set UseDpi to true to view the image at its original resolution 
      _imageViewer.UseDpi = True 
 
      ' Add Pan/Zoom interactive mode 
      ' Click and drag to pan, CTRL-Click and drag to zoom in and out 
      _imageViewer.DefaultInteractiveMode = New ImageViewerPanZoomInteractiveMode() 
 
      ' Initialize the zoom system 
      InitZoom(zoomComboBox, zoomInButton, zoomOutButton) 
 
      ' Load an image 
      Using codecs As New RasterCodecs() 
         _imageViewer.Image = codecs.Load(Path.Combine(ImagesPath.Path, "Ocr1.tif")) 
      End Using 
 
      MyBase.OnLoad(e) 
   End Sub 
 
   Private Sub UpdateZoomValueFromView() 
      ' Get the current scale factor from the viewer and set it in the zoom combo box 
      Dim percentage As Double = _imageViewer.ScaleFactor * 100.0 
      Dim zoomComboBox As ComboBox = TryCast(Me.Controls.Find("zoomComboBox", True)(0), ComboBox) 
      zoomComboBox.Text = percentage.ToString("F1") & "%" 
   End Sub 
 
   Private Sub InitZoom(ByVal zoomComboBox As ComboBox, ByVal zoomInButton As Button, ByVal zoomOutButton As Button) 
      ' Add support for user typing the zoom value in the combo box directly 
      AddHandler zoomComboBox.LostFocus, 
         Sub(sender, e) 
            ' When the user moves away from the combo box, make sure it has a valid value 
            UpdateZoomValueFromView() 
         End Sub 
 
      AddHandler zoomComboBox.KeyPress, 
         Sub(sender, e) 
            ' Check if the finished editing by pressing Enter 
            If e.KeyChar = ChrW(Keys.Return) Then 
               ' Yes, get the new value 
               Dim value As String = zoomComboBox.Text.Trim() 
               If (Not String.IsNullOrEmpty(value)) Then 
                  ' Remove the % sign if present 
                  If value.EndsWith("%") Then 
                     value = value.Remove(value.Length - 1, 1).Trim() 
                  End If 
 
                  ' Try to parse the new zoom value 
                  Dim percentage As Double 
                  If Double.TryParse(value, percentage) Then 
                     ' Valid value, zoom the viewer 
                     _imageViewer.Zoom(ControlSizeMode.None, percentage / 100.0, _imageViewer.DefaultZoomOrigin) 
                  End If 
 
                  ' And update the combo box from this value (in case we set a value not in the min/max range) 
                  UpdateZoomValueFromView() 
               End If 
            End If 
         End Sub 
 
      AddHandler zoomComboBox.SelectedIndexChanged, 
         Sub(sender, e) 
            ' Get the value from the combo box 
            Dim value As String = zoomComboBox.Text.Trim() 
            Select Case value 
               Case "Actual Size" 
                  _imageViewer.Zoom(ControlSizeMode.ActualSize, 1, _imageViewer.DefaultZoomOrigin) 
 
               Case "Fit Page" 
                  _imageViewer.Zoom(ControlSizeMode.FitAlways, 1, _imageViewer.DefaultZoomOrigin) 
 
               Case "Fit Width" 
                  _imageViewer.Zoom(ControlSizeMode.FitWidth, 1, _imageViewer.DefaultZoomOrigin) 
 
               Case "Fit Height" 
                  _imageViewer.Zoom(ControlSizeMode.FitHeight, 1, _imageViewer.DefaultZoomOrigin) 
 
               Case Else 
                  If (Not String.IsNullOrEmpty(value)) Then 
                     ' A percentage, use it 
                     Dim percentage As Double = Double.Parse(value.Substring(0, value.Length - 1)) 
                     _imageViewer.Zoom(ControlSizeMode.None, percentage / 100.0, _imageViewer.DefaultZoomOrigin) 
                  End If 
            End Select 
         End Sub 
 
      ' For zoom in button, use current ScaleFactor multiplied by the ratio 
      AddHandler zoomInButton.Click, 
         Sub(sender, e) 
            _imageViewer.Zoom(ControlSizeMode.None, _imageViewer.ScaleFactor * _zoomRatio, _imageViewer.DefaultZoomOrigin) 
         End Sub 
 
      ' For zoom out button, use current ScaleFactor divided by the ratio 
      AddHandler zoomOutButton.Click, 
         Sub(sender, e) 
            _imageViewer.Zoom(ControlSizeMode.None, _imageViewer.ScaleFactor / _zoomRatio, _imageViewer.DefaultZoomOrigin) 
         End Sub 
 
      ' Also update the value from the viewer when the transform changed, this happens if the user selects a fit mode, 
      ' such as fit width or fit page. The viewer will change the scale factor accordingly and we need to update it 
      ' in our combo box 
      ' This also takes care of Pan/Zoom interactive mode updating the scale factor 
      AddHandler _imageViewer.TransformChanged, 
         Sub(sender, e) 
            UpdateZoomValueFromView() 
         End Sub 
 
      ' Get the value from the viewer into the combo box 
      UpdateZoomValueFromView() 
   End Sub 
End Class