ImageViewerVirtualizer Class

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
<TestMethod> 
Public Sub ImageViewerVirtualizer_Example() 
   Dim imageFileName As String = GetExampleImageFile() 
 
   ' Create a new form to test out virtualizer 
   Dim form As MyForm = New MyForm(imageFileName) 
   form.ShowDialog() 
End Sub 
 
Private Shared Function GetExampleImageFile() As String 
   Dim imageFileName As String = Path.Combine(ImagesPath.Path, "ImageViewerVirtualizerExample.tif") 
 
   ' Check if it is previously created, return it 
   If File.Exists(imageFileName) Then 
      Return imageFileName 
   End If 
 
   ' Create an image that has many pages, we will use that for out testing 
   Const pageCount As Integer = 100 
   Const imageWidth As Integer = 800 
   Const imageHeight As Integer = 800 
 
   Dim rc As New Rectangle(0, 0, imageWidth, imageHeight) 
 
   Using codecs As RasterCodecs = New RasterCodecs() 
      Using font As Font = New Font(FontFamily.GenericMonospace, 80) 
         For page As Integer = 1 To pageCount 
            Using image As RasterImage = RasterImage.Create(imageWidth, imageHeight, 24, 96, RasterColor.FromKnownColor(RasterKnownColor.White)) 
               Dim hdc As IntPtr = RasterImagePainter.CreateLeadDC(image) 
               Using graphics As Graphics = graphics.FromHdc(hdc) 
                  graphics.DrawRectangle(Pens.Blue, 0, 0, rc.Width - 1, rc.Height - 1) 
                  TextRenderer.DrawText(graphics, "Page " & page.ToString(), font, rc, Color.Red, TextFormatFlags.HorizontalCenter Or TextFormatFlags.VerticalCenter) 
               End Using 
               RasterImagePainter.DeleteLeadDC(hdc) 
 
               If page = 1 Then 
                  codecs.Save(image, imageFileName, RasterImageFormat.TifLzw, 0, 1, -1, -1, CodecsSavePageMode.Overwrite) 
               Else 
                  codecs.Save(image, imageFileName, RasterImageFormat.TifLzw, 0, 1, -1, -1, CodecsSavePageMode.Append) 
               End If 
            End Using 
         Next page 
      End Using 
   End Using 
 
   Return imageFileName 
End Function 
 
 
' Custom Virtualizer 
Public Class MyVirtualizer : Inherits ImageViewerVirtualizer 
   Private _imageFileName As String 
   Public Sub New(ByVal imageFileName As String) 
      MyBase.New() 
      _imageFileName = imageFileName 
      ' We will load 4 items at a time 
      Me.MaximumItems = 4 
   End Sub 
 
   Protected Overrides Function LoadItem(ByVal item As ImageViewerItem) As Object 
      ' Load a page, the page number is the item index + 1, but it 
      ' could be anything in your application, for example 
      ' using ImageViewerItem.Tag to store the necessary data to identity this item 
      Dim pageNumber As Integer = Me.ImageViewer.Items.IndexOf(item) + 1 
      Using codecs As RasterCodecs = New RasterCodecs() 
         Return codecs.Load(_imageFileName, pageNumber) 
      End Using 
   End Function 
 
   Protected Overrides Sub SaveItem(ByVal item As ImageViewerItem, ByVal data As Object) 
      ' Nothing to do in this application, just log it. 
      ' If save is required, then this is the place to do it 
      Dim pageNumber As Integer = Me.ImageViewer.Items.IndexOf(item) + 1 
      System.Diagnostics.Debug.WriteLine("SaveItem for page {0} is called") 
   End Sub 
 
   Protected Overrides Sub DeleteItem(ByVal item As ImageViewerItem, ByVal data As Object) 
      ' Dispose the image 
      Dim image As RasterImage = TryCast(data, RasterImage) 
      If Not image Is Nothing Then 
         image.Dispose() 
      End If 
   End Sub 
 
   Protected Overrides Sub RenderItemPlaceholder(ByVal e As ImageViewerRenderEventArgs) 
      ' Render the place holder for this page 
      Dim pageNumber As Integer = Me.ImageViewer.Items.IndexOf(e.Item) + 1 
      Dim transform As LeadMatrix = Me.ImageViewer.GetItemImageTransform(e.Item) 
 
      Dim graphics As Graphics = e.PaintEventArgs.Graphics 
 
      ' Render the message at 0,0 in this item transformation 
      Dim pt As LeadPointD = LeadPointD.Create(0, 0) 
      pt = transform.Transform(pt) 
      Dim message As String = String.Format("Loading page {0}...", pageNumber) 
      graphics.DrawString(message, Me.ImageViewer.Font, Brushes.Black, CSng(pt.X), CSng(pt.Y)) 
   End Sub 
End Class 
 
' Form to test the virtualizer 
Private Class MyForm : Inherits Form 
   Public Sub New(ByVal imageFileName As String) 
      _imageFileName = imageFileName 
   End Sub 
 
   Private _imageViewer As ImageViewer 
   Private _imageFileName As String 
 
   Protected Overrides Sub OnLoad(ByVal e As EventArgs) 
      ' Create a new image viewer with vertical layout 
      Dim viewLayout As New ImageViewerVerticalViewLayout 
      viewLayout.Columns = 1 
      Dim _imageViewer As New ImageViewer(viewLayout) 
      _imageViewer.BackColor = Color.Bisque 
      _imageViewer.Dock = DockStyle.Fill 
 
      ' Add pan zoom interactive mode 
      _imageViewer.InteractiveModes.Add(New ImageViewerPanZoomInteractiveMode()) 
 
      Me.Controls.Add(_imageViewer) 
      _imageViewer.BringToFront() 
 
      ' Add empty items, each one with the correct size but with 
      Using codecs As RasterCodecs = New RasterCodecs() 
         Dim pageCount As Integer 
         Dim pageSize As LeadSize 
         Dim pageResolution As LeadSizeD 
 
         Using info As CodecsImageInfo = codecs.GetInformation(_imageFileName, True) 
            pageCount = info.TotalPages 
            pageSize = LeadSize.Create(info.Width, info.Height) 
            pageResolution = LeadSizeD.Create(info.XResolution, info.YResolution) 
         End Using 
 
         _imageViewer.BeginUpdate() 
         Dim page As Integer = 1 
         Do While page <= pageCount 
            ' no image data, the virtualizer will take care of loading the pages and rendering them 
            Dim item As ImageViewerItem = New ImageViewerItem() 
            item.ImageSize = pageSize 
            item.Resolution = pageResolution 
            _imageViewer.Items.Add(item) 
            page += 1 
         Loop 
         _imageViewer.EndUpdate() 
      End Using 
 
      ' Finally, set our virtualizer so it can start working 
      _imageViewer.Virtualizer = New MyVirtualizer(_imageFileName) 
 
      ' Run the demo, use pan (drag) and zoom (CTRL-CLICK and drag) to show the items 
      ' Note how they get loaded when they are in view 
      ' Change the number of MaximumItems to see its effect. 
 
      MyBase.OnLoad(e) 
   End Sub 
End Class