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StartOverlay Method
See Also  Example
Leadtools.Codecs Namespace > RasterCodecs Class : StartOverlay Method




callback
The method which should be called when an overlay is detected. Use a null reference (Nothing in Visual Basic) to indicate that LEADTOOLS should handle overlays automatically.
mode
Indicates when should this method be called. See CodecsOverlayCallbackMode for possible values.
Indicates which method should be called when an overlay is detected inside a file.

Syntax

Visual Basic (Declaration) 
Public Sub StartOverlay( _
   ByVal callback As CodecsOverlayCallback, _
   ByVal mode As CodecsOverlayCallbackMode _
)
Visual Basic (Usage)Copy Code
Dim instance As RasterCodecs
Dim callback As CodecsOverlayCallback
Dim mode As CodecsOverlayCallbackMode
 
instance.StartOverlay(callback, mode)
C# 
public void StartOverlay( 
   CodecsOverlayCallback callback,
   CodecsOverlayCallbackMode mode
)
Managed Extensions for C++ 
public: void StartOverlay( 
   CodecsOverlayCallback* callback,
   CodecsOverlayCallbackMode mode
)
C++/CLI 
public:
void StartOverlay( 
   CodecsOverlayCallback^ callback,
   CodecsOverlayCallbackMode mode
)

Parameters

callback
The method which should be called when an overlay is detected. Use a null reference (Nothing in Visual Basic) to indicate that LEADTOOLS should handle overlays automatically.
mode
Indicates when should this method be called. See CodecsOverlayCallbackMode for possible values.

Example

Visual BasicCopy Code
RasterCodecs.StartOverlay
      Private Sub PtokaOverlayExample(ByVal ptokaFileName As String, ByVal ptokaFilesPath As String)
         RasterCodecs.Startup()
         Dim codecs As RasterCodecs = New RasterCodecs()
         Dim destFileName As String = "C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\PtokaOverlay.tif"

         ' Set up the private variables used in the callback
         myCodecs = codecs
         myPtokaFilesPath = ptokaFilesPath

         ' Set the overlay callback
         codecs.StartOverlay(AddressOf MyOverlayCallback, CodecsOverlayCallbackMode.CallLoad)

         ' Load the PTOKA file
         Dim image As RasterImage = codecs.Load(ptokaFileName)

         ' Stop the overlay by resetting the old callback.
         codecs.StopOverlay()

         ' Save the image as TIFF
         codecs.Save(image, destFileName, RasterImageFormat.Tif, 1)
         image.Dispose()

         ' Clean up
         codecs.Dispose()
         RasterCodecs.Shutdown()
      End Sub

      Private myCodecs As RasterCodecs
      Private myPtokaFilesPath As String

      Private Sub MyOverlayCallback(ByVal data As CodecsOverlayData)
         ' Show overlay information
         Console.WriteLine("File: {0}", data.FileName)
         Console.WriteLine("Page Number: {0}", data.PageNumber)
         Console.WriteLine("Info: {0}", data.Info)

         ' Construct the overlay file name
         Dim overlayFileName As String = Path.Combine(myPtokaFilesPath, data.FileName)

         If data.Info Then
            ' Info, we only need to fill in the .InfoXXX members of the data
            Dim imageInfo As CodecsImageInfo = myCodecs.GetInformation(overlayFileName, False)
            data.InfoWidth = imageInfo.Width
            data.InfoHeight = imageInfo.Height
            data.InfoXResolution = imageInfo.XResolution
            data.InfoYResolution = imageInfo.YResolution
         Else
            ' We need to load the overlay image into the .Image member
            data.Image = myCodecs.Load(overlayFileName)
         End If
      End Sub
C#Copy Code
RasterCodecs.StartOverlay 
      void PtokaOverlayExample(string ptokaFileName, string ptokaFilesPath) 
      { 
         RasterCodecs.Startup(); 
         RasterCodecs codecs = new RasterCodecs(); 
         string destFileName = @"C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\PtokaOverlay.tif"; 
 
         // Set up the private variables used in the callback 
         myCodecs = codecs; 
         myPtokaFilesPath = ptokaFilesPath; 
 
         // Set the overlay callback 
         codecs.StartOverlay(MyOverlayCallback, CodecsOverlayCallbackMode.CallLoad); 
 
         // Load the PTOKA file 
         RasterImage image = codecs.Load(ptokaFileName); 
 
         // Stop the overlay by resetting the old callback. 
         codecs.StopOverlay(); 
 
         // Save the image as TIFF 
         codecs.Save(image, destFileName, RasterImageFormat.Tif, 1); 
         image.Dispose(); 
 
         // Clean up 
         codecs.Dispose(); 
         RasterCodecs.Shutdown(); 
      } 
 
      RasterCodecs myCodecs; 
      string myPtokaFilesPath; 
 
      void MyOverlayCallback(CodecsOverlayData data) 
      { 
         // Show overlay information 
         Console.WriteLine("File: {0}", data.FileName); 
         Console.WriteLine("Page Number: {0}", data.PageNumber); 
         Console.WriteLine("Info: {0}", data.Info); 
 
         // Construct the overlay file name 
         string overlayFileName = Path.Combine(myPtokaFilesPath, data.FileName); 
 
         if(data.Info) 
         { 
            // Info, we only need to fill in the .InfoXXX members of the data 
            CodecsImageInfo imageInfo = myCodecs.GetInformation(overlayFileName, false); 
            data.InfoWidth = imageInfo.Width; 
            data.InfoHeight = imageInfo.Height; 
            data.InfoXResolution = imageInfo.XResolution; 
            data.InfoYResolution = imageInfo.YResolution; 
         } 
         else 
         { 
            // We need to load the overlay image into the .Image member 
            data.Image = myCodecs.Load(overlayFileName); 
         } 
      }

Remarks

Currently, only PTOCA files are known to use such overlays.

PTOCA files contain file references (ie filenames) to external files that contain overlay bitmaps. (These files are typically in IOCA format)

These external overlay files will be resized and placed on the current page according to the information from the PTOCA files. By default, LEADTOOLS will load these external overlay files from disk. You should override this behaviour if you load files that are not stored locally (eg: on a remote storage or in a database).

To load overlays stored on other storage, you have to pass your overlay callback to this method and load the overlays in your overlay callback.

The overlay callback will be used until StopOverlay is called.

Requirements

Target Platforms: Microsoft .NET Framework 2.0, Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also