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DeleteTag(string,int,int) Method

Summary

Deletes a tag from a file, if the file supports tags (TIFF or Exif).

Syntax
C#
VB
Objective-C
C++
public void DeleteTag( 
   string fileName, 
   int pageNumber, 
   int id 
) 
Public Overloads Sub DeleteTag( _ 
   ByVal fileName As String, _ 
   ByVal pageNumber As Integer, _ 
   ByVal id As Integer _ 
)  
- (BOOL)deleteTag:(NSUInteger)tagId  
         fromFile:(NSString *)file  
       pageNumber:(NSInteger)pageNumber  
            error:(NSError **)error 
public: 
void DeleteTag(  
   String^ fileName, 
   int pageNumber, 
   int id 
)  

Parameters

fileName
A String containing the name of the file from which to delete the tag.

pageNumber
The 1-based index of the page from which the tag will be deleted. Use -1 to delete the tag from the last page. Use 1 to delete the tag from the first page.

id
The ID of the tag in the TIFF file. The tag IDs are between 0 and 65535.

Remarks

If you want to delete the tag from a particular IFD in the file, set RasterCodecs.Options.Tiff.Save.UseImageFileDirectoryOffset to true, and set RasterCodecs.Options.Tiff.Save.ImageFileDirectoryOffset to the IFD in question. This method will delete tags only from the main IFDs that make up an image. Some TIFF tags are themselves SubIFDs. You can delete tags from such SubIFDs by using RasterCodecs.Options.Tiff.Save.UseImageFileDirectoryOffset and RasterCodecs.Options.Tiff.Save.ImageFileDirectoryOffset specifying the IFD as above.

Notes:

  • The Leadtools.Codecs.Cmp.dll codec is used to delete the tag from all the TIFF and Exif files.
  • Do not attempt to use this method to delete tags from inside the TagFound event. If you want to delete tags that you enumerate, use the TagFound event to add the tags to a list. Upon returning from EnumTags, you can delete all the tags from the list.
  • You should be careful when you delete non-custom tags (tags below 32768). If you delete the wrong tag, you might corrupt the TIF file!.

When you add or remove tags, the tags array at the end of the file is re-written. When you modify existing tags, the new tag value is added to the file and the IFD is modified as necessary. In all of these cases, there is no image recompression.

Example

This example will create a TIF file, add a certain tag to it then delete it

C#
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
using LeadtoolsExamples.Common; 
 
public void TagExample() 
{ 
   RasterCodecs codecs = new RasterCodecs(); 
 
   string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"); 
   string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1_PageNumberTag.tif"); 
 
   // Convert the source file to TIF 
   Console.WriteLine("Converting the source file to TIF"); 
   codecs.Convert(srcFileName, destFileName, RasterImageFormat.Tif, 0, 0, 24, null); 
 
   const int pageNumberTagId = 297; 
   int pageNumber = 7; 
 
   RasterTagMetadata writeTag = new RasterTagMetadata(); 
   writeTag.Id = pageNumberTagId; 
   writeTag.DataType = RasterTagMetadataDataType.Int32; 
   writeTag.FromInt32(new int[] { pageNumber }); 
 
   Console.WriteLine("Writing the following tag to the file:"); 
   Console.WriteLine("  ID: {0}", writeTag.Id); 
   Console.WriteLine("  DataType: {0}", writeTag.DataType); 
   Console.Write("  Data: "); 
   byte[] writeTagData = writeTag.GetData(); 
   for (int i = 0; i < writeTagData.Length; i++) 
      Console.Write("{0:X} ", writeTagData[i]); 
   Console.WriteLine(); 
 
   // Add the tag 
   Console.WriteLine("Writing the page number tag with data = {0} to the file", pageNumber); 
   codecs.WriteTag(destFileName, 1, writeTag); 
 
   // Read the tag and make sure its in the file 
   Console.WriteLine("Reading the page number tag from the file"); 
   RasterTagMetadata readTag = codecs.ReadTag(destFileName, 1, pageNumberTagId); 
 
   Console.WriteLine("Tag read from the file:"); 
   Console.WriteLine("  ID: {0}", readTag.Id); 
   Console.WriteLine("  DataType: {0}", readTag.DataType); 
   Console.Write("  Data: "); 
   byte[] readTagData = readTag.GetData(); 
   for (int i = 0; i < readTagData.Length; i++) 
      Console.Write("{0:X} ", readTagData[i]); 
   Console.WriteLine(); 
 
   Debug.Assert(writeTag.Id == readTag.Id); 
   Debug.Assert(writeTag.DataType == readTag.DataType); 
   Debug.Assert(writeTagData.Length == writeTagData.Length); 
   for (int i = 0; i < writeTagData.Length; i++) 
      Debug.Assert(writeTagData[i] == readTagData[i]); 
 
   // Delete the tag from the file 
   Console.WriteLine("Deleting the tag from the file"); 
   codecs.DeleteTag(destFileName, 1, pageNumberTagId); 
 
   // Make sure the tag is deleted 
   Console.WriteLine("Reading the tag from the file again"); 
   readTag = codecs.ReadTag(destFileName, 1, pageNumberTagId); 
 
   if (readTag == null) 
      Console.WriteLine("Tag was not found"); 
   else 
      Console.WriteLine("Tag is found, this should not happen"); 
 
   Debug.Assert(readTag == null); 
 
   // Clean up 
   codecs.Dispose(); 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images"; 
} 

Requirements

Target Platforms

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