HitTestZone Method

'Declaration
 
Function HitTestZone( _
   ByVal point As LogicalPoint _
) As Integer

' Assume Form1 is a Windwos.Forms form in your application
      ' The OCR engine we are using
      Private _ocrEngine As IOcrEngine
      Private _ocrDocument As IOcrDocument

      ' Our raster image viewer instance
      Private _viewer As RasterImageViewer

      Public Sub New()
         InitializeComponent()

         ' Initialize the raster image viewer
         ' Turn on use DPI, center the image, add border padding and frame shadow to show that our calculations will be
         ' independent on all of those extra options
         _viewer = New RasterImageViewer()
         _viewer.Dock = DockStyle.Fill
         _viewer.BackColor = SystemColors.AppWorkspace
         _viewer.UseDpi = True
         _viewer.BorderPadding.All = 8
         _viewer.FrameSize = New SizeF(1, 1)
         _viewer.FrameShadowSize = New SizeF(2, 2)
         _viewer.SizeMode = RasterPaintSizeMode.Normal
         _viewer.HorizontalAlignMode = RasterPaintAlignMode.Center
         _viewer.VerticalAlignMode = RasterPaintAlignMode.Center
         _viewer.AutoDisposeImages = True
         _viewer.InteractiveMode = RasterViewerInteractiveMode.None

         ' Turn on scale to gray painting in the viewer
         Dim props As RasterPaintProperties = _viewer.PaintProperties
         props.PaintDisplayMode = props.PaintDisplayMode Or RasterPaintDisplayModeFlags.ScaleToGray
         _viewer.PaintProperties = props

         ' Subscribe to the viewer events we need
         AddHandler _viewer.KeyDown, AddressOf _viewer_KeyDown
         AddHandler _viewer.MouseDown, AddressOf _viewer_MouseDown
         AddHandler _viewer.PostImagePaint, AddressOf _viewer_PostImagePaint

         Controls.Add(_viewer)
         _viewer.BringToFront()

         ' Create and startup the OCR engine
         _ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.Plus, False)
         _ocrEngine.Startup(Nothing, Nothing, Nothing, Nothing)

         ' Create the OCR document
         _ocrDocument = _ocrEngine.DocumentManager.CreateDocument()

         ' Load an image into the document
         Dim tifFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif")
         Dim ocrPage As IOcrPage = _ocrDocument.Pages.AddPage(tifFileName, Nothing)

         ' Do auto zone
         ocrPage.AutoZone(Nothing)

         ' AutoZone does not specify a name for the zones, so loop through all the zones and set their names
         ' to a unique value. We will use the name in the paint code later
         Dim ocrZones As IOcrZoneCollection = ocrPage.Zones
         For i As Integer = 0 To ocrZones.Count - 1
            Dim ocrZone As OcrZone = ocrZones(i)

            ' Construct the name from the ID
            ocrZone.Name = String.Format("Zone {0}", ocrZone.Id)

            ocrZones(i) = ocrZone
         Next

         ' Show the same image in the viewer
         _viewer.Image = ocrPage.GetRasterImage()

         ' Note, the image we got from GetRasterImage is a copy of the image in the engine
         ' Since we set teh AutoDisposeImages of the viewer to "true", the image will be disposed
         ' when the viewer is disposed at application termination

         Text = "+ to zoom in, - to zoom out, enter to return to 100%. Select the zones with the mouse"
      End Sub

      Protected Overrides Sub OnFormClosed(ByVal e As FormClosedEventArgs)
         ' Destroy the document
         _ocrDocument.Dispose()

         ' Shutdown the OCR engine
         _ocrEngine.Shutdown()
         _ocrEngine.Dispose()

         MyBase.OnFormClosed(e)
      End Sub

      Private Sub _viewer_KeyDown(ByVal sender As Object, ByVal e As KeyEventArgs)
         Const zoomRatio As Double = 1.2
         Dim scaleFactor As Double = _viewer.ScaleFactor

         Select Case (e.KeyCode)
            Case Keys.Add, Keys.Oemplus
               ' Zoon in
               scaleFactor *= zoomRatio
               e.Handled = True

            Case Keys.Subtract, Keys.OemMinus
               ' Zone out
               scaleFactor /= zoomRatio
               e.Handled = True

            Case Keys.Enter
               scaleFactor = 1
               e.Handled = True
         End Select

         Const minimumScaleFactor As Double = 0.05
         Const maximumScaleFactor As Double = 11

         scaleFactor = Math.Max(minimumScaleFactor, Math.Min(maximumScaleFactor, scaleFactor))

         ' Check if scale factor has changed
         If (scaleFactor <> _viewer.ScaleFactor) Then
            _viewer.BeginUpdate()

            ' Yes, zoom keeping the center of the image

            ' Get what you see in physical coordinates
            Dim rc As Rectangle = Rectangle.Intersect(_viewer.PhysicalViewRectangle, _viewer.ClientRectangle)
            ' Get the center of what you see in physical coordinates
            Dim center As New PointF(rc.Left + rc.Width \ 2, rc.Top + rc.Height \ 2)
            Dim t As New Transformer(_viewer.Transform)
            ' Get the center of what you see in logical coordinates
            center = t.PointToLogical(center)

            _viewer.ScaleFactor = scaleFactor

            ' Bring the original center into the view center
            t = New Transformer(_viewer.Transform)
            ' Get the center of what you saw before the zoom in physical coordinates
            center = t.PointToPhysical(center)
            ' Bring the old center into the center of the view
            _viewer.CenterAtPoint(Point.Round(center))

            _viewer.EndUpdate()
         End If
      End Sub

      Private Sub _viewer_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs)
         ' Perform hit-testing on the zones
         If (Not _ocrEngine Is Nothing) AndAlso (_ocrEngine.IsStarted) AndAlso (_ocrDocument.Pages.Count > 0) AndAlso e.Button = Windows.Forms.MouseButtons.Left Then
            ' Get the transform of the viewer
            ' Use the transform that takes the DPI into consideration since we turned that on
            Using matrix As Matrix = _viewer.GetTransformWithDpi()
               Dim t As New Transformer(matrix)

               ' Convert the mouse click coordinates from physical (viewer) to logical (image)
               Dim point As New PointF(e.X, e.Y)
               point = t.PointToLogical(point)

               ' Hit test the zones
               ' An alternitave to calling HitTestZone is to loop through all the zones
               ' and get the value of .Bounds in pixels, then check if the point is inside
               ' the boundaries.
               Dim ocrPage As IOcrPage = _ocrDocument.Pages(0)
               Dim lPoint As LeadPoint = New LeadPoint(CType(point.X, Integer), CType(point.Y, Integer))
               Dim zoneIndex As Integer = ocrPage.HitTestZone(New LogicalPoint(lPoint))

               If (zoneIndex <> -1) Then
                  ' We hit a zone, loop through all the zones, unselect all but the hit tested zone
                  For index As Integer = 0 To ocrPage.Zones.Count - 1
                     ' Since OcrZone is a structure, we cannot simply do
                     ' ocrZone.Zones[index].Selected = value
                     ' We have to get a copy of the structure, modify it and set it back

                     Dim ocrZone As OcrZone = ocrPage.Zones(index)

                     If (index <> zoneIndex) Then
                        ocrZone.Selected = False
                     Else
                        ocrZone.Selected = True
                     End If

                     ocrPage.Zones(index) = ocrZone
                  Next

                  ' Re-paint the viewer to show the new zones
                  _viewer.Invalidate()
               End If
            End Using
         End If
      End Sub

      Private Sub _viewer_PostImagePaint(ByVal sender As Object, ByVal e As PaintEventArgs)
         ' Draw the zones on the viewer in their correct location
         If (Not _ocrEngine Is Nothing) AndAlso (_ocrEngine.IsStarted) AndAlso (_ocrDocument.Pages.Count > 0) Then
            ' Get the transform of the viewer
            ' Use the transform that takes the DPI into consideration since we turned that on
            Using matrix As Matrix = _viewer.GetTransformWithDpi()
               Dim t As New Transformer(matrix)

               Dim ocrPage As IOcrPage = _ocrDocument.Pages(0)

               Dim normalPen As New Pen(Color.Blue, 1)
               Dim selectedPen As New Pen(Color.Red, 2)
               selectedPen.DashStyle = DashStyle.Dash

               For Each ocrZone As OcrZone In ocrPage.Zones
                  ' Get the zone bounds in pixels
                  ' You can also use ocrPage.GetZoneBoundsInPixels here

                  Dim ltzoneBounds As LeadRect = ocrZone.Bounds.ToRectangle(ocrPage.DpiX, ocrPage.DpiY)
                  Dim zoneBounds As RectangleF = New RectangleF(ltzoneBounds.Left, ltzoneBounds.Top, ltzoneBounds.Width, ltzoneBounds.Height)

                  ' This rectangle is in image (logical) coordinates with top-left view perspective
                  ' Convert to the physical coordinates of the viewer
                  zoneBounds = t.RectangleToPhysical(zoneBounds)

                  ' Now draw this zone on the viewer surface
                  If (ocrZone.Selected) Then
                     e.Graphics.DrawRectangle(selectedPen, zoneBounds.X, zoneBounds.Y, zoneBounds.Width - 1, zoneBounds.Height - 1)
                  Else
                     e.Graphics.DrawRectangle(normalPen, zoneBounds.X, zoneBounds.Y, zoneBounds.Width - 1, zoneBounds.Height - 1)
                  End If

                  ' Draw the zone name on the left hand corner of the zone
                  ' Note, in a real application you might want to have an option to show/hide the zone names (labels)
                  Dim labelSize As SizeF = e.Graphics.MeasureString(ocrZone.Name, Font)
                  Dim labelRectangle As New RectangleF(zoneBounds.X, zoneBounds.Y - labelSize.Height, labelSize.Width, labelSize.Height)
                  e.Graphics.FillRectangle(Brushes.Yellow, labelRectangle)
                  e.Graphics.DrawString(ocrZone.Name, Font, Brushes.Black, labelRectangle.X, labelRectangle.Y)
               Next
            End Using
         End If
      End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class