ReadTag(string,int,int) Method

Summary

Gets the specified tagged data from a TIFF file.

Syntax

Objective-C

C++/CLI

Python

public RasterTagMetadata ReadTag( 
   string fileName, 
   int pageNumber, 
   int id 
)

- (nullable LTRasterTagMetadata *)readTag:(NSUInteger)tagId  
                                 fromFile:(NSString *)file  
                               pageNumber:(NSInteger)pageNumber  
                                    error:(NSError **)error

public: 
RasterTagMetadata^ ReadTag(  
   String^ fileName, 
   int pageNumber, 
   int id 
)

def ReadTag(self,fileName,pageNumber,id):

Parameters

fileName
A String containing the input file name.

pageNumber
1-based index of the page from which to read the tag.

id
Tag to identify the data in the TIFF file (or file format that supports Exif metadata). Use the same tag that you specified in the WriteTag. Examples of registered tags are:

Value	Meaning
0x8298	Copyright comment
0x8769	General Exif comments
0x8825	Exif GPS comments
0x80A4	Annotation TIFF tag

Return Value

The tag data.

Remarks

This method is provided to support TIFF tags that you define. If no such tag exists in the image, this method will return a null reference.

To read all the tags stored in a file, use ReadTags

You can use TagsSupported to determine whether a certain file format supports tags.

Example

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
 
 
 
public void TagExample() 
{ 
   RasterCodecs codecs = new RasterCodecs(); 
 
   string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"); 
   string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1_CustomTag.tif"); 
 
   // Convert the source file to TIF 
   Debug.WriteLine("Converting the source file to TIF"); 
   codecs.Convert(srcFileName, destFileName, RasterImageFormat.Tif, 0, 0, 24, null); 
 
   const int customTagId = 0x8000; /* 32768 in decimal */ 
   int customTagValue = 7; 
 
   RasterTagMetadata writeTag = new RasterTagMetadata(); 
   writeTag.Id = customTagId; 
   writeTag.DataType = RasterTagMetadataDataType.Int32; 
   writeTag.FromInt32(new int[] { customTagValue }); 
 
   Debug.WriteLine("Writing the following tag to the file:"); 
   Debug.WriteLine("  ID: {0}", writeTag.Id); 
   Debug.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]); 
   Debug.WriteLine(" "); 
 
   // Add the tag 
   Debug.WriteLine("Writing the custom tag with data = {0} to the file", customTagValue); 
   codecs.WriteTag(destFileName, 1, writeTag); 
 
   // Read the tag and make sure its in the file 
   Debug.WriteLine("Reading the custom tag from the file"); 
   RasterTagMetadata readTag = codecs.ReadTag(destFileName, 1, customTagId); 
 
   Debug.WriteLine("Tag read from the file:"); 
   Debug.WriteLine("  ID: {0}", readTag.Id); 
   Debug.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]); 
   Debug.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 
   Debug.WriteLine("Deleting the tag from the file"); 
   codecs.DeleteTag(destFileName, 1, customTagId); 
 
   // Make sure the tag is deleted 
   Debug.WriteLine("Reading the tag from the file again"); 
   readTag = codecs.ReadTag(destFileName, 1, customTagId); 
 
   if (readTag == null) 
      Debug.WriteLine("Tag was not found"); 
   else 
      Debug.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:\LEADTOOLS22\Resources\Images"; 
}