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ReadTags(String,Int32) Method
See Also  Example
Leadtools.Codecs Namespace > RasterCodecs Class > ReadTags Method : ReadTags(String,Int32) Method



fileName
A String containing the input file name.
pageNumber
1-based index of the page from which to read the tags.
Reads all the tags stored in a TIFF file.

Syntax

Visual Basic (Declaration) 
Public Overloads Function ReadTags( _
   ByVal fileName As String, _
   ByVal pageNumber As Integer _
) As RasterCollection(Of RasterTagMetadata)
Visual Basic (Usage)Copy Code
Dim instance As RasterCodecs
Dim fileName As String
Dim pageNumber As Integer
Dim value As RasterCollection(Of RasterTagMetadata)
 
value = instance.ReadTags(fileName, pageNumber)
C# 
public RasterCollection<RasterTagMetadata> ReadTags( 
   string fileName,
   int pageNumber
)
C++/CLI 
public:
RasterCollection<RasterTagMetadata> ReadTags( 
   String^ fileName,
   int pageNumber
)

Parameters

fileName
A String containing the input file name.
pageNumber
1-based index of the page from which to read the tags.

Return Value

A collection of RasterTagMetadata containing all the tags found in the file. If the file does not contain any tags, an empty collection will be returned. If the file format does not support tags, an exception will be thrown.

Example

This example will load all the metadata (tags, geo-keys and comments) found in a disk file.

Visual BasicCopy Code
Public Sub MetadataLoadExample()
   ' Prompt the user for an image file
   Dim imageFileName As String
   Using dlg As New OpenFileDialog()
      dlg.Title = "Browse to file to load its meta data"
      dlg.Filter = "All Files|*.*"
      dlg.InitialDirectory = "C:\Users\Public\Documents\LEADTOOLS Images"
      If dlg.ShowDialog() = DialogResult.OK Then
         imageFileName = dlg.FileName
      Else
         Return
      End If
   End Using

   ' Initialize LEADTOOLS
   RasterCodecs.Startup()
   Using codecs As New RasterCodecs()
      ' Get the file format
      Dim format As RasterImageFormat

      Using info As CodecsImageInfo = codecs.GetInformation(imageFileName, False)
         format = info.Format
      End Using

      ' Load the tags
      Dim tags As RasterCollection(Of RasterTagMetadata) = Nothing
      If RasterCodecs.TagsSupported(format) Then
         tags = codecs.ReadTags(imageFileName, 1)
      End If

      ' Load the comments
      Dim comments As RasterCollection(Of RasterCommentMetadata) = Nothing
      If RasterCodecs.CommentsSupported(format) Then
         comments = codecs.ReadComments(imageFileName, 1)
      End If

      ' Load the geo keys
      Dim geoKeys As RasterCollection(Of RasterTagMetadata) = Nothing
      If RasterCodecs.GeoKeysSupported(format) Then
         geoKeys = codecs.ReadGeoKeys(imageFileName, 1)
      End If

      Dim txtFileName As String = Path.Combine( _
         Path.GetDirectoryName(imageFileName), _
         Path.GetFileNameWithoutExtension(imageFileName) + "_metadata.txt")

      Using writer As StreamWriter = File.CreateText(txtFileName)
         ' Write the tags
         WriteTags(writer, "Tags", tags)

         ' Write the comments
         WriteComments(writer, comments)

         ' Write the geo keys (tags and geokeys use the same data type)
         WriteTags(writer, "GeoKeys", geoKeys)
      End Using

      ' Show the text file we created
      System.Diagnostics.Process.Start(txtFileName)
   End Using
   RasterCodecs.Shutdown()
End Sub

Private Shared Sub WriteTags(ByVal writer As StreamWriter, ByVal name As String, ByVal tags As RasterCollection(Of RasterTagMetadata))
   writer.WriteLine("{0}:", name)

   If Not IsNothing(tags) Then
      For Each tag As RasterTagMetadata In tags
         writer.WriteLine("Id: 0x{0}, data length: {1}", tag.Id.ToString("X"), tag.GetData().Length)
      Next
   Else
      writer.WriteLine("Not supported")
   End If

   writer.WriteLine()
End Sub

Private Shared Sub WriteComments(ByVal writer As StreamWriter, ByVal comments As RasterCollection(Of RasterCommentMetadata))
   writer.WriteLine("Comments:")

   If Not IsNothing(comments) Then
      For Each comment As RasterCommentMetadata In comments
         writer.WriteLine("Type: {0}, data length: {1}", comment.Type, comment.GetData().Length)
      Next
   Else
      writer.WriteLine("Not supported")
   End If

   writer.WriteLine()
End Sub
C#Copy Code
public void MetadataLoadExample() 
{ 
   // Prompt the user for an image file 
   string imageFileName; 
   using(OpenFileDialog dlg = new OpenFileDialog()) 
   { 
      dlg.Title = "Browse to file to load its meta data"; 
      dlg.Filter = "All Files|*.*"; 
      dlg.InitialDirectory = @"C:\Users\Public\Documents\LEADTOOLS Images"; 
      if(dlg.ShowDialog() == DialogResult.OK) 
         imageFileName = dlg.FileName; 
      else 
         return; 
   } 
 
   // Initialize LEADTOOLS 
   RasterCodecs.Startup(); 
   using(RasterCodecs codecs = new RasterCodecs()) 
   { 
      // Get the file format 
      RasterImageFormat format; 
 
      using(CodecsImageInfo info = codecs.GetInformation(imageFileName, false)) 
      { 
         format = info.Format; 
      } 
 
      // Load the tags 
      RasterCollection<RasterTagMetadata> tags = null; 
      if(RasterCodecs.TagsSupported(format)) 
         tags = codecs.ReadTags(imageFileName, 1); 
 
      // Load the comments 
      RasterCollection<RasterCommentMetadata> comments = null; 
      if(RasterCodecs.CommentsSupported(format)) 
         comments = codecs.ReadComments(imageFileName, 1); 
 
      // Load the geo keys 
      RasterCollection<RasterTagMetadata> geoKeys = null; 
      if(RasterCodecs.GeoKeysSupported(format)) 
         geoKeys = codecs.ReadGeoKeys(imageFileName, 1); 
 
      string txtFileName = Path.Combine( 
         Path.GetDirectoryName(imageFileName), 
         Path.GetFileNameWithoutExtension(imageFileName) + "_metadata.txt"); 
 
      using(StreamWriter writer = File.CreateText(txtFileName)) 
      { 
         // Write the tags 
         WriteTags(writer, "Tags", tags); 
 
         // Write the comments 
         WriteComments(writer, comments); 
 
         // Write the geo keys (tags and geokeys use the same data type) 
         WriteTags(writer, "GeoKeys", geoKeys); 
      } 
 
      // Show the text file we created 
      System.Diagnostics.Process.Start(txtFileName); 
   } 
   RasterCodecs.Shutdown(); 
} 
 
private static void WriteTags(StreamWriter writer, string name, RasterCollection<RasterTagMetadata> tags) 
{ 
   writer.WriteLine("{0}:", name); 
 
   if(tags != null) 
   { 
      foreach(RasterTagMetadata tag in tags) 
      { 
         writer.WriteLine("Id: 0x{0}, data length: {1}", tag.Id.ToString("X"), tag.GetData().Length); 
      } 
   } 
   else 
   { 
      writer.WriteLine("Not supported"); 
   } 
 
   writer.WriteLine(); 
} 
 
private static void WriteComments(StreamWriter writer, RasterCollection<RasterCommentMetadata> comments) 
{ 
   writer.WriteLine("Comments:"); 
 
   if(comments != null) 
   { 
      foreach(RasterCommentMetadata comment in comments) 
      { 
         writer.WriteLine("Type: {0}, data length: {1}", comment.Type, comment.GetData().Length); 
      } 
   } 
   else 
   { 
      writer.WriteLine("Not supported"); 
   } 
 
   writer.WriteLine(); 
}

Remarks

To read a specific tag stored in a file, use ReadTag and to enumerate all the tag ids (but not the data) stored in a file use EnumTags.

This method will throw an exception if the file format does not support tags. To check if a file format supports tags, use RasterCodecs.TagsSupported. You can also automatically load all the tags stored in a file during a load operation by setting the CodecsLoadOptions.Tags property to true. The tags data will be stored in the result image RasterImage.Tags collection.

To load all the tags stored in a stream containing the image data, use ReadTags.

Requirements

Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family

See Also