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HitTestZone Method

Summary
Gets the zero-based index of the zone under a certain point.
Syntax
C#
Objective-C
C++/CLI
Java
Python
public int HitTestZone( 
   LeadPoint point 
) 
- (NSUInteger)hitTestZone:(LeadPoint)point 
public int hitTestZone(LeadPoint point) 
int HitTestZone(  
   LeadPoint point 
)  
def HitTestZone(self,point): 

Parameters

point
The test point in pixels.

Return Value

The zero-based index of the zone under  point, if no zone is under the test point, this method will return -1.

Remarks

You can use this method to check whether a zone (either added manually or automatically) is under a given test point. For example, if you have a Windows Forms based application with the current IOcrPage in an ImageViewer control. You might want to draw the zones on the surface of the viewer. For this, you can use the GetZoneBoundsInPixels methods. If you want to allow the user to click with the mouse on the viewer to select and de-select zones, you can use HitTestZone.

Example

This example will view the OCR Page and its zones in an ImageViewer control. It will then allow the user to select/deselect zones with the mouse.

C#
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Ocr; 
using Leadtools.Forms.Common; 
using Leadtools.Document.Writer; 
using Leadtools.WinForms; 
using Leadtools.Drawing; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
// Assume Form1 is a Windows.Forms form in your application 
 
// The OCR engine we are using 
private IOcrEngine _ocrEngine; 
// The OCR page we are using 
private IOcrPage _ocrPage; 
 
// Our raster image viewer instance 
private RasterImageViewer _viewer; 
 
public Form1() 
{ 
   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 
   RasterPaintProperties props = _viewer.PaintProperties; 
   props.PaintDisplayMode |= RasterPaintDisplayModeFlags.ScaleToGray; 
   _viewer.PaintProperties = props; 
 
   // Subscribe to the viewer events we need 
   _viewer.KeyDown += new KeyEventHandler(_viewer_KeyDown); 
   _viewer.MouseDown += new MouseEventHandler(_viewer_MouseDown); 
   _viewer.PostImagePaint += new PaintEventHandler(_viewer_PostImagePaint); 
 
   Controls.Add(_viewer); 
   _viewer.BringToFront(); 
 
   // Create and startup the OCR engine 
   _ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD); 
   _ocrEngine.Startup(null, null, null, LEAD_VARS.OcrLEADRuntimeDir); 
 
   // Load an image into the OCR document 
   string tifFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif"); 
   _ocrPage = _ocrEngine.CreatePage(_ocrEngine.RasterCodecsInstance.Load(tifFileName, 1), OcrImageSharingMode.AutoDispose); 
 
   // Do auto zone 
   _ocrPage.AutoZone(null); 
 
   // 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 
   IOcrZoneCollection ocrZones = _ocrPage.Zones; 
   for (int i = 0; i < ocrZones.Count; i++) 
   { 
      OcrZone ocrZone = ocrZones[i]; 
 
      // Construct the name from the ID 
      ocrZone.Name = string.Format("Zone {0}", ocrZone.Id); 
 
      ocrZones[i] = ocrZone; 
   } 
 
   // 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 the 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"; 
} 
 
protected override void OnFormClosed(FormClosedEventArgs e) 
{ 
   // Dispose the page 
   _ocrPage.Dispose(); 
 
   // Shutdown the OCR engine 
   _ocrEngine.Dispose(); 
 
   base.OnFormClosed(e); 
} 
 
private void _viewer_KeyDown(object sender, KeyEventArgs e) 
{ 
   const double zoomRatio = 1.2; 
   double scaleFactor = _viewer.ScaleFactor; 
 
   switch (e.KeyCode) 
   { 
      case Keys.Add: 
      case Keys.Oemplus: 
         // Zoom in 
         scaleFactor *= zoomRatio; 
         e.Handled = true; 
         break; 
 
      case Keys.Subtract: 
      case Keys.OemMinus: 
         // Zone out 
         scaleFactor /= zoomRatio; 
         e.Handled = true; 
         break; 
 
      case Keys.Enter: 
         scaleFactor = 1; 
         e.Handled = true; 
         break; 
   } 
 
   const double minimumScaleFactor = 0.05; 
   const double maximumScaleFactor = 11; 
 
   scaleFactor = Math.Max(minimumScaleFactor, Math.Min(maximumScaleFactor, scaleFactor)); 
 
   // Check if scale factor has changed 
   if (scaleFactor != _viewer.ScaleFactor) 
   { 
      _viewer.BeginUpdate(); 
 
      // Yes, zoom keeping the center of the image 
 
      // Get what you see in physical coordinates 
      Rectangle rc = Rectangle.Intersect(_viewer.PhysicalViewRectangle, _viewer.ClientRectangle); 
      // Get the center of what you see in physical coordinates 
      PointF center = new PointF(rc.Left + rc.Width / 2, rc.Top + rc.Height / 2); 
      Transformer t = 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(); 
   } 
} 
 
private void _viewer_MouseDown(object sender, MouseEventArgs e) 
{ 
   // Perform hit-testing on the zones 
   if (_ocrEngine != null && _ocrEngine.IsStarted && _ocrPage != null && e.Button == MouseButtons.Left) 
   { 
      // Get the transform of the viewer 
      // Use the transform that takes the DPI into consideration since we turned that on 
      using (Matrix matrix = _viewer.GetTransformWithDpi()) 
      { 
         Transformer t = new Transformer(matrix); 
 
         // Convert the mouse click coordinates from physical (viewer) to logical (image) 
         PointF point = new PointF(e.X, e.Y); 
         point = t.PointToLogical(point); 
 
         // Hit test the zones 
         // An alternative 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. 
         LeadPoint lPoint = new LeadPoint((int)point.X, (int)point.Y); 
         int zoneIndex = _ocrPage.HitTestZone(lPoint); 
         if (zoneIndex != -1) 
         { 
            // We hit a zone, loop through all the zones, unselect all but the hit tested zone 
            for (int index = 0; index < _ocrPage.Zones.Count; index++) 
            { 
               // Since OcrZone is a structure, we cannot simply do 
               // ocrZone.Zones[index].Name = value 
               // We have to get a copy of the structure, modify it and set it back 
 
               OcrZone ocrZone = _ocrPage.Zones[index]; 
 
               if (index != zoneIndex) 
                  ocrZone.Name = null; 
               else 
                  ocrZone.Name = "Selected"; 
 
               _ocrPage.Zones[index] = ocrZone; 
            } 
 
            // Re-paint the viewer to show the new zones 
            _viewer.Invalidate(); 
         } 
      } 
   } 
} 
 
private void _viewer_PostImagePaint(object sender, PaintEventArgs e) 
{ 
   // Draw the zones on the viewer in their correct location 
   if (_ocrEngine != null && _ocrEngine.IsStarted && _ocrPage != null) 
   { 
      // Get the transform of the viewer 
      // Use the transform that takes the DPI into consideration since we turned that on 
      using (Matrix matrix = _viewer.GetTransformWithDpi()) 
      { 
         Transformer t = new Transformer(matrix); 
 
         Pen normalPen = new Pen(Color.Blue, 1); 
         Pen selectedPen = new Pen(Color.Red, 2); 
         selectedPen.DashStyle = DashStyle.Dash; 
 
         foreach (OcrZone ocrZone in _ocrPage.Zones) 
         { 
            // Get the zone bounds in pixels 
            // You can also use _ocrPage.GetZoneBoundsInPixels here 
            RectangleF zoneBounds = new RectangleF(ocrZone.Bounds.Left, ocrZone.Bounds.Top, ocrZone.Bounds.Width, ocrZone.Bounds.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.Name == "Selected") 
               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); 
 
            // 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) 
            SizeF labelSize = e.Graphics.MeasureString(ocrZone.Name, Font); 
            RectangleF labelRectangle = 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); 
         } 
      } 
   } 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
   public const string OcrLEADRuntimeDir = @"C:\LEADTOOLS23\Bin\Common\OcrLEADRuntime"; 
} 
Requirements

Target Platforms

Help Version 23.0.2024.3.3
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Leadtools.Ocr Assembly

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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.