Saving and Reading TIFF Tags and Comments

Take the following steps to start a project and to add some code that reads and writes comments and tags:

Start Visual Studio .NET.
Choose File->New->Project… from the menu.
In the New Project dialog box, choose either "Visual C# Projects" or "Visual Basic Projects" in the Projects Type List, and choose "Windows Application " in the Templates List.
Type the project name as "Saving and Reading Tiff Tags and Comments" in the Project Name field, and then click OK. If desired, type a new location for your project or select a directory using the Browse button, and then click OK.
In the "Solution Explorer" window, right-click on the "References" folder, and select "Add Reference…" from the context menu. In the "Add Reference" dialog box, select the ".NET" tab and browse to the "<LEADTOOLS_INSTALLDIR>\Bin\DotNet\Win32 "folder and select the following DLLs:
- Leadtools.dll
- Leadtools.Codecs.dll
- Leadtools.Codecs.Fax.dll
- Leadtools.Codecs.Tif.dll
Click the Select button and then press the OK button to add the above DLLs to the application.

Switch to Form1 code view (right-click Form1 in the solution explorer then select View Code ) and add the following lines at the beginning of the file:

[Visual Basic]


             Imports Leadtools
             Imports Leadtools.Codecs

[C#]


             using Leadtools;
             using Leadtools.Codecs;

Add an event handler to the Form1 Load event and add the following code:

[Visual Basic]


             Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
                ' Initialize a new RasterCodecs object
                codecs = New RasterCodecs()
             End Sub

[C#]


             private void Form1_Load(object sender, System.EventArgs e)
             {
                // Initialize a new RasterCodecs object
                codecs = new RasterCodecs();
             }

Add the following variable to the Form1 class:

[C#]


            ' the RasterCodecs object for loading/saving images
            Private codecs As RasterCodecs

[C#]


            // the RasterCodecs object for loading/saving images
            private RasterCodecs codecs;

Drag and drop a button onto Form1. Change the following properties:

Property	Value
Name:	btnCommentReadWrite
Text:	Comment Read\Write

Add the following code for the btnCommentReadWrite control’s click procedure:

Visual Basic


             Private Sub btnCommentReadWrite_Click(ByVal sender As System.Object, ByVal e 
               Dim ofd As OpenFileDialog = New OpenFileDialog()
               Try
                  ofd.Filter = "Tif files (*.tif)|*.tif|All files (*.*)|*.*"
                  If ofd.ShowDialog() = DialogResult.OK Then
                     'Write the comment to the file
                     Dim writeComment As RasterCommentMetadata = New RasterCommentMetadata()
                     writeComment.Type = RasterCommentMetadataType.Software
                     writeComment.FromAscii("LEADTOOLS Demo")
                     codecs.WriteComment(ofd.FileName, 1, writeComment)
                     'Read The Comment
                     Dim readComment As RasterCommentMetadata = codecs.ReadComment(ofd.FileName, 1, RasterCommentMetadataType.Software)
                     MessageBox.Show(readComment.ToAscii(), "The following comment has been read:")
                  End If
               Finally
                  ofd.Dispose()
               End Try
             End Sub


             private void btnCommentReadWrite_Click(object sender, EventArgs e)
             {
               using (OpenFileDialog ofd = new OpenFileDialog())
               {
                  ofd.Filter = "Tif files (*.tif)|*.tif|All files (*.*)|*.*";
                  if (ofd.ShowDialog() == DialogResult.OK)
                  {
                     //Write the comment to the file
                     RasterCommentMetadata writeComment = new RasterCommentMetadata();
                     writeComment.Type = RasterCommentMetadataType.Software;
                     writeComment.FromAscii("LEADTOOLS Demo");
                     codecs.WriteComment(ofd.FileName, 1, writeComment);
                     //Read The Comment
                     RasterCommentMetadata readComment =
                     codecs.ReadComment(ofd.FileName, 1, RasterCommentMetadataType.Software);
                     MessageBox.Show(readComment.ToAscii(), "The following comment has been read:");
                  }
               }
             }

To read or write TIFF tags, drag and drop a button onto Form1. Change the following properties:

Property	Value
Name:	btnReadWriteTags
Text:	Read\WriteTags

Add the following code for the btnReadWriteTags control’s click procedure:

Visual Basic


             Private Sub btnReadWriteTags_Click(ByVal sender As System.Object, 
                                                ByVal e As System.EventArgs) Handles btnReadWriteTags.Click
               Dim ofd As OpenFileDialog = New OpenFileDialog()
               Try
                  ofd.Filter = "Tif files (*.tif)|*.tif|All files (*.*)|*.*"
                  If ofd.ShowDialog() = DialogResult.OK Then
                     'This code reads the Xresolution from a TIFF image and modifies the value and saves it back.
                     Const XresTagID As Integer = 282
                     Dim tag As RasterTagMetadata
                     tag = New RasterTagMetadata()
                     Dim ReadTag As RasterTagMetadata = codecs.ReadTag(ofd.FileName, 1, XresTagID)
                     Dim rational As RasterMetadataURational() = ReadTag.ToURational()
                     rational(0).Numerator = rational(0).Numerator * 5
                     rational(0).Denominator = rational(0).Denominator * 1
                     ReadTag.FromURational(rational)
                     codecs.WriteTag(ofd.FileName, 1, ReadTag)
                     MessageBox.Show("Resolution changed successfully.")
                  End If
               Finally
                  ofd.Dispose()
               End Try
             End Sub


             private void btnReadWriteTags_Click(object sender, EventArgs e)
             {
               using (OpenFileDialog ofd = new OpenFileDialog())
               {
                  ofd.Filter = "Tif files (*.tif)|*.tif|All files (*.*)|*.*";
                  if (ofd.ShowDialog() == DialogResult.OK)
                  {
                     //This code reads the Xresolution from a TIFF image and modifies the value and saves it back.
                     const int XresTagID = 282;
                     RasterTagMetadata tag;
                     tag = new RasterTagMetadata();
                     RasterTagMetadata ReadTag = codecs.ReadTag(ofd.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(ofd.FileName, 1, ReadTag);
                     MessageBox.Show("Resolution changed successfully.");
                  }
               }
             }

Note: Normally you do not have to modify this Tag because LEADTOOLS automatically sets the resolution tags to the bitmap's DPI values whenever the Save method is used. This code only shows how to modify it without loading and saving the image itself.

Compile and run your project.