ITextSharp：从表单字段中删除字符限制

2 回答

• 3

  如果您了解PDF格式的内部结构，这很容易！下面的代码与code I wrote for a different type of PDF annotation here几乎相同 . 该页面将更详细地解释一些内容，并为您提供一些参考 . 但基本上诀窍是遍历每个页面，然后遍历每个页面的注释（表单字段属于此类别等），然后查找设置了最大长度的文本字段，并删除该限制 . 所有这些工作都是在一个只读的 PdfReader 对象上完成的，所以一旦我们完成，我们需要再次循环并使用某种 PdfWriter 将其写回 .

  下面是一个完整的C＃2010 WinForms应用程序，目标是iTextSharp 5.2.1，它显示了所有这些 . 有关更多详细信息，请参阅代码中的注释 .

  using System;
  using System.IO;
  using System.Windows.Forms;
  using iTextSharp.text;
  using iTextSharp.text.pdf;
  
  namespace WindowsFormsApplication1 {
      public partial class Form1 : Form {
          public Form1() {
              InitializeComponent();
          }
  
          private void Form1_Load(object sender, EventArgs e) {
              var inputFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "test.pdf");
              var outputFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "output.pdf");
  
              //Setup some variables to be used later
              PdfDictionary PageDictionary = default(PdfDictionary);
              PdfArray Annots = default(PdfArray);
  
              //Bind a reader to our input PDF
              PdfReader R = new PdfReader(inputFile);
              //Store the number of pages
              int PageCount = R.NumberOfPages;
              //Loop through each page remember that page numbers start at 1
              for (int i = 1; i <= PageCount; i++) {
                  //Get the current page
                  PageDictionary = R.GetPageN(i);
  
                  //Get all of the annotations for the current page
                  Annots = PageDictionary.GetAsArray(PdfName.ANNOTS);
  
                  //Make sure we have something
                  if ((Annots == null) || (Annots.Length == 0)) { continue; }
  
                  //Loop through each annotation
                  foreach (PdfObject A in Annots.ArrayList) {
                      //Convert the itext-specific object as a generic PDF object
                      PdfDictionary AnnotationDictionary = (PdfDictionary)PdfReader.GetPdfObject(A);
  
                      //See if this annotation has a WIDGET which would be the UI implementation of a form field
                      if (!AnnotationDictionary.Get(PdfName.SUBTYPE).Equals(PdfName.WIDGET)) { continue; }
  
                      //See if this annotation is a text field (TX)
                      if (!AnnotationDictionary.Get(PdfName.FT).Equals(PdfName.TX)) { continue; }
  
                      //See if it has a maximum length specified (MAXLEN)
                      if (AnnotationDictionary.Contains(PdfName.MAXLEN)) {
                          //If so, remove it
                          AnnotationDictionary.Remove(PdfName.MAXLEN);
                      }
                  }
              }
              //Next we create a new document add import each page from the reader above
              using (FileStream FS = new FileStream(outputFile, FileMode.Create, FileAccess.Write, FileShare.None)) {
                  using (Document Doc = new Document()) {
                      using (PdfCopy writer = new PdfCopy(Doc, FS)) {
                          Doc.Open();
                          for (int i = 1; i <= R.NumberOfPages; i++) {
                              writer.AddPage(writer.GetImportedPage(R, i));
                          }
                          Doc.Close();
                      }
                  }
              }
          }
      }
  }
  

  回复于 2024-04-16T15:30:02+08:00
• 0

  我能够使用Chris提供的信息来解决这个问题 . 我试图在设置值之前删除任何字段上的任何最大长度限制 .

  //TargetObject is an AcroFields object
              AcroFields.Item item = TargetObject.GetFieldItem({FieldName});
              if (item != null)
              {
                  foreach (var i in item.merged)
                  {
                      if (i.GetType() == typeof(PdfDictionary))
                      {
                          PdfDictionary dictionary = (PdfDictionary)i;
                          if (dictionary.Contains(PdfName.MAXLEN))
                          {
                              dictionary.Remove(PdfName.MAXLEN);
                          }
                          break; //no need to continue once we find the dictionary and remove max length
                      }
                  }
              }
  

  回复于 2024-04-16T15:30:02+08:00