Read and Write TIFF Tags and Comments - C# .NET 6

This tutorial shows how to read and write TIFF tags and comments in a C# .NET 6 application using the LEADTOOLS SDK.

Required Knowledge

Get familiar with the basic steps of creating a project by reviewing the Add References and Set a License tutorial, before working on this tutorial.

Create the Project and Add LEADTOOLS References

Start with a copy of the project created in the Add References and Set a License tutorial. If you do not have that project, follow the steps in that tutorial to create it.

The references needed depend upon the purpose of the project. References can be added via NuGet packages.

This tutorial requires the following NuGet package:

• Leadtools.Formats.Raster.Common

For a complete list of which DLL files are required for your application, refer to Files to be Included With Your Application.

Set the License File

The License unlocks the features needed for the project. It must be set before any toolkit function is called. For details, including tutorials for different platforms, refer to Setting a Runtime License.

There are two types of runtime licenses:

• Evaluation license, obtained at the time the evaluation toolkit is downloaded. It allows the toolkit to be evaluated.
• Deployment license. If a Deployment license file and developer key are needed, refer to Obtaining a License.

Add the Read/Write TIFF Comments Code

With the project created, the references added, and the license set, coding can begin.

In the Solution Explorer, open Program.cs. Add the following variables to the using block at the top of Program.cs.

using System; 
using System.IO; 
using Leadtools; 
using Leadtools.Codecs; 

In the Program class, add the following variables in the Program class before Main(). Add the new string fileName and set the new string value to the file path containing the TIFF file. Next, add the new string multiPageTif and set the new string value to the file path if one will be used.

public static string fileName = @"C:\LEADTOOLS23\Resources\Images\clean.tif"; 
public static string multiPageTif = @""; // Update to path location to a MultiPage Tiff 

In the Program class, add a new method named ReadAndWriteTifComments(string fileName) to the Program class. Call it in the Main() method as shown below.

static void Main(string[] args) 
{ 
    InitLEAD(); 
 
    ReadAndWriteTifComments(fileName); 
    ReadAndWriteTifTags(fileName); 
    ReadAndWriteTagsToMultipageTif(multiPageTif); 
} 

Add the code below to the ReadAndWriteTifComments() method to write a comment to the TIFF file, then read the comment and display it to the console.

static void ReadAndWriteTifComments(string fileName) 
{ 
    using (RasterCodecs codecs = new RasterCodecs()) 
    { 
        // Write the comment to the file 
        RasterCommentMetadata writeComment = new RasterCommentMetadata(); 
        writeComment.Type = RasterCommentMetadataType.Software; 
        writeComment.FromAscii("LEADTOOLS Demo"); 
        codecs.WriteComment(fileName, 1, writeComment); 
        // Read The Comment 
        RasterCommentMetadata readComment = 
        codecs.ReadComment(fileName, 1, RasterCommentMetadataType.Software); 
        Console.WriteLine("The following comment has been read:\n" + 
            $"{readComment.ToAscii()}/n"); 
    } 
} 

Note

Because the RasterCodecs class implements IDisposable, make sure it is in a using statement for proper disposal.

Add the Read/Write TIFF Tags Code

In the Program class, add a new method named ReadAndWriteTifTags(string fileName), and call it in the Main() method after ReadAndWriteTifComments(), as shown above. Add the below code to the new method to read the XResolution of the TIFF image, modify the value, and write the tag to the file.

static void ReadAndWriteTifTags(string fileName) 
{ 
    using (RasterCodecs codecs = new RasterCodecs()) 
    { 
        // This code reads the Xresolution from a TIFF image, modifies the value, and saves it back. 
        const int XresTagID = 282; 
        RasterTagMetadata ReadTag = codecs.ReadTag(fileName, 1, XresTagID); 
        RasterMetadataURational[] rational = ReadTag.ToURational(); 
        rational[0].Numerator = rational[0].Numerator * 5; 
        rational[0].Denominator = rational[0].Denominator * 1; 
        ReadTag.FromURational(rational); 
        codecs.WriteTag(fileName, 1, ReadTag); 
        Console.WriteLine("Resolution changed successfully."); 
    } 
} 

Add Read/Write support for Multipage TIFF files

In the Program class, add a new method named ReadAndWriteTagsToMultipageTif(string fileName), and call it in the Main() method after the ReadAndWriteTifTags() method, as shown above. Add the below code to the new method to read the PageName for each page in a MultiPage TIFF file, and then save the values in a new file.

static void ReadAndWriteTagsToMultipageTif(string fileName) 
{ 
    if (!(String.IsNullOrEmpty(multiPageTif))) 
    { 
        // This code reads the PageName for each page in a MultiPage TIFF file, and then saves the values in a new file. 
        using (RasterCodecs codecs = new RasterCodecs()) 
        { 
            const int TIFFTAG_PAGENAME = 285; 
 
            CodecsImageInfo imageInfo = codecs.GetInformation(multiPageTif, true); 
            int totalpages = imageInfo.TotalPages; 
            codecs.Options.Load.Tags = true; 
            codecs.Options.Save.Tags = true; 
 
 
            for (int i = 1; i <= totalpages; i++) 
            { 
                var rasterImage = codecs.Load(multiPageTif, i); 
                codecs.ReadTag(multiPageTif, i, TIFFTAG_PAGENAME).ToAscii(); 
                Console.WriteLine(codecs.ReadTag(multiPageTif, i, TIFFTAG_PAGENAME).ToAscii()); 
 
                codecs.Save(rasterImage, "output.tif", RasterImageFormat.TifJpeg411, 0, 1, 1, 1, CodecsSavePageMode.Append); 
                Console.WriteLine(codecs.ReadTag("output.tif", i, TIFFTAG_PAGENAME).ToAscii()); 
            } 
        } 
    } 
} 

Run the Project

Run the project by pressing F5, or by selecting Debug -> Start Debugging.

If the steps were followed correctly, the console appears and the application writes a new TIFF comment and then displays the comment in the console. Then, the application reads the XResolution from the TIFF image, modifies the resolution value and writes the tag back to the TIFF image. The application will also write TIFF comments to a new multipage TIFF if one is provided.

Wrap-up

This tutorial showed how to use the RasterTagMetadata and RasterCommentMetadata classes to read/write TIFF comments and tags.

See Also

• LEADTOOLS RasterCommentMetadata Documentation
• LEADTOOLS RasterTagMetadata Documentation
• LEADTOOLS RasterCodecs Documentation
• LEADTOOLS SDK Download