StartOverlay Method

C#
Visual Basic
WinRT C#
Java
Objective-C
WinRT JavaScript
C++

public void StartOverlay( 
   CodecsOverlayCallback callback,
   CodecsOverlayCallbackMode mode
)

'Declaration

Public Sub StartOverlay( _
   ByVal callback As CodecsOverlayCallback, _
   ByVal mode As CodecsOverlayCallbackMode _
)

'Usage

Dim instance As RasterCodecs
Dim callback As CodecsOverlayCallback
Dim mode As CodecsOverlayCallbackMode
 
instance.StartOverlay(callback, mode)

public void StartOverlay( 
   CodecsOverlayCallback callback,
   CodecsOverlayCallbackMode mode
)

- (BOOL)startOverlay:(nullable LTCodecsOverlayCallback)callback 
                mode:(LTCodecsOverlayCallbackMode)mode 
               error:(NSError **)error

public void startOverlay(CodecsOverlayListener listener, CodecsOverlayCallbackMode mode)

 function Leadtools.Codecs.RasterCodecs.StartOverlay( 
   callback ,
   mode 
)

public:
void StartOverlay( 
   CodecsOverlayCallback^ callback,
   CodecsOverlayCallbackMode mode
)

Parameters

callback: The method which should be called when an overlay is detected. Use a null reference to indicate that LEADTOOLS should handle overlays automatically.
mode: Indicates when this method should be called. See CodecsOverlayCallbackMode for possible values.

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

PTOCA files contain file references (i.e. 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 behavior if you load files that are not stored locally (for example, 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.

This example will read a PTOKA file and overlays a TIF file on it

C#
Visual Basic
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color
Imports Leadtools.Drawing
Imports Leadtools.Svg

Private Sub PtokaOverlayExample(ByVal ptokaFileName As String, ByVal ptokaFilesPath As String)
   Dim codecs As RasterCodecs = New RasterCodecs()
   Dim destFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "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()
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

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

using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;
using Leadtools.Svg;

void PtokaOverlayExample(string ptokaFileName, string ptokaFilesPath)
{
   RasterCodecs codecs = new RasterCodecs();
   string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "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 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);
   }
}

static class LEAD_VARS
{
public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

Target Platforms

Reference

RasterCodecs Class
RasterCodecs Members