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ReadTags(string,int) Method

Summary

Reads all the tags stored in a TIFF file.

Syntax
C#
VB
Objective-C
C++
public IList<RasterTagMetadata> ReadTags( 
   string fileName, 
   int pageNumber 
) 
Public Overloads Function ReadTags( _ 
   ByVal fileName As String, _ 
   ByVal pageNumber As Integer _ 
) As IList(Of RasterTagMetadata) 
- (nullable NSArray<LTRasterTagMetadata *> *)readTagsFromFile:(NSString *)file  
                                                   pageNumber:(NSInteger)pageNumber  
                                                        error:(NSError **)error 
public: 
IList<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.

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 determine whether a file format supports tags, use 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 resulting image RasterImage.Tags collection.

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

Example

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

C#
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
using LeadtoolsExamples.Common; 
 
public void MetadataLoadExample() 
{ 
   // Prompt the user for an image file 
   string imageFileName = PromptForFileName(); 
 
   // Initialize LEADTOOLS 
   using (RasterCodecs codecs = new RasterCodecs()) 
   { 
      // Get the file format 
      RasterImageFormat format; 
 
      using (CodecsImageInfo info = codecs.GetInformation(imageFileName, false)) 
      { 
         format = info.Format; 
      } 
 
      // Load the tags 
      IList<RasterTagMetadata> tags = null; 
      if (RasterCodecs.TagsSupported(format)) 
         tags = codecs.ReadTags(imageFileName, 1); 
 
      // Load the comments 
      IList<RasterCommentMetadata> comments = null; 
      if (RasterCodecs.CommentsSupported(format)) 
         comments = codecs.ReadComments(imageFileName, 1); 
 
      // Load the geo keys 
      IList<RasterTagMetadata> geoKeys = null; 
      if (RasterCodecs.GeoKeysSupported(format)) 
         geoKeys = codecs.ReadGeoKeys(imageFileName, 1); 
 
      // Load the markers 
      IList<RasterMarkerMetadata> markers = null; 
      if (RasterCodecs.MarkersSupported(format)) 
         markers = codecs.ReadMarkers(imageFileName); 
 
      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); 
 
         // Write the markers 
         WriteMarkers(writer, markers); 
      } 
 
      // Show the text file we created 
      System.Diagnostics.Process.Start(txtFileName); 
   } 
} 
 
private static void WriteTags(StreamWriter writer, string name, IList<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, IList<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(); 
} 
 
private static void WriteMarkers(StreamWriter writer, IList<RasterMarkerMetadata> markers) 
{ 
   writer.WriteLine("Markers:"); 
 
   if (markers != null) 
   { 
      foreach (RasterMarkerMetadata marker in markers) 
      { 
         writer.WriteLine("ID: {0}, data length: {1}", marker.Id, marker.GetData().Length); 
      } 
   } 
   else 
   { 
      writer.WriteLine("Not supported"); 
   } 
 
   writer.WriteLine(); 
} 

Requirements

Target Platforms

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Leadtools.Codecs Assembly