How to retrieve form field bounds from rotated PDF document using C#

The Syncfusion Essential® PDF is a feature-rich and high performance .NET PDF library used to create, read, and edit PDF documents programmatically without Adobe dependencies. Using this library, you can get the form field bounds on the rotated PDF document page using C#.

Steps to get a form field bounds on a rotated PDF page programmatically:

1. Create a new console application project.
2. Install the Syncfusion.Pdf.Net.Core NuGet package as a reference to your console application from Nuget.org.
   
3. Include the following namespaces in the Program.cs file.

C#

using Syncfusion.Drawing;
using Syncfusion.Pdf;
using Syncfusion.Pdf.Graphics;
using Syncfusion.Pdf.Parsing;

4. Use the following code sample in Program.cs to retrieve the bounds of the form fields on a rotated page.
   C#

// Open the PDF file
FileStream inputFileStream = new FileStream(@"../../../Input.pdf", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
// Load the PDF document
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(inputFileStream);
// Get the form from the loaded document
PdfLoadedForm loadedForm = loadedDocument.Form;
// Get the collection of form fields
PdfLoadedFormFieldCollection fieldCollection = loadedForm?.Fields;
// Iterate through each field in the form field collection
foreach (var field in fieldCollection)
{
   // Check if the field is a text box field
   if (field is PdfLoadedTextBoxField loadedField)
   {
       // Get the bounds of the field considering the page rotation
       var bounds = GetRoatedPageFieldBound(loadedField);

       // Draw a red rectangle around the text box field
       loadedField.Page.Graphics.DrawRectangle(PdfBrushes.Red, bounds);
   }
}

// Create a memory stream to save the modified PDF document
using MemoryStream stream = new MemoryStream();
// Save the modified document to the memory stream
loadedDocument.Save(stream);
// Close the PDF document
loadedDocument.Close(true);
// Reset the memory stream position to the beginning
stream.Position = 0;
// Write the modified PDF document to a new file
File.WriteAllBytes(@"Output.pdf", stream.ToArray());

/// <summary>
/// Get the bounds of the field considering the page rotation.
/// </summary>
/// <param name="loadedSignField">The text box field. </param>
/// <returns>The bounds of the field as a RectangleF. </returns>
RectangleF GetRoatedPageFieldBound(PdfLoadedTextBoxField loadedSignField)
{
   // Get the page containing the field
   PdfLoadedPage loadedPage = loadedSignField.Page as PdfLoadedPage;
   float locationX = 0;
   float locationY = 0;
   PointF location = PointF.Empty;
   SizeF size = SizeF.Empty;

   // Adjust the bounds based on the page rotation
   switch (loadedPage.Rotation)
   {
       case PdfPageRotateAngle.RotateAngle0:
           return loadedSignField.Bounds;

       case PdfPageRotateAngle.RotateAngle90:
           locationX = loadedPage.Size.Height - (loadedSignField.Location.Y + loadedSignField.Bounds.Height);
           locationY = loadedSignField.Location.X;
           location = new PointF(locationX, locationY);
           size = new SizeF(loadedSignField.Size.Height, loadedSignField.Size.Width);
           return new RectangleF(location, size);

       case PdfPageRotateAngle.RotateAngle180:
           locationX = loadedPage.Size.Width - (loadedSignField.Location.X + loadedSignField.Size.Width);
           locationY = loadedPage.Size.Height - (loadedSignField.Bounds.Y + loadedSignField.Size.Height);
           location = new PointF(locationX, locationY);
           size = new SizeF(loadedSignField.Size.Width, loadedSignField.Size.Height);
           return new RectangleF(location, size);

       case PdfPageRotateAngle.RotateAngle270:
           locationX = loadedSignField.Location.Y;
           locationY = loadedPage.Size.Width - loadedSignField.Location.X - loadedSignField.Size.Width;
           location = new PointF(locationX, locationY);
           size = new SizeF(loadedSignField.Size.Height, loadedSignField.Size.Width);
           return new RectangleF(location, size);

       default:
           return loadedSignField.Bounds;
   }
}

A complete working sample can be downloaded from Interactive_Elements_on_Rotated_Page.zip

By executing the program, you will get the PDF document as follows.

Take a moment to peruse the documentation for working with pages, where you will find other options like inserting, removing, and rearranging pages in PDF document, adding margin, and importing pages from the existing PDF document.

Refer here to explore the rich set of Syncfusion Essential® PDF features.