iTextSharp的4.1.6 - 刪除從PDF模板

Question

既有線我在LibreOffice中創建的PDF模板，我加油吧使用AcroFields。在一些罕見的情況下，我想隱藏一個特定的字段，因此我使用RemoveField方法將其刪除。它是邊界，但留在那裏。從我搜索的內容看來，它可能是LibreOffice創建表單的方式。

我已經與到目前爲止想出了是讓現場的矩形，並用白色圖像覆蓋。然而問題是，客戶使用計劃，使我目前的解決方案几乎無法使用

的問題因此背景圖像和/或其他背景顏色較白的創建模板 - 是有一些方法我可以去掉的邊界？ [例如。通過訪問iTextSharp的一些低級別的對象模型，或類似的東西]

感謝很多提前

Answer 1

卸下單獨的圖形對象可能會變得有些棘手，但它不是不可能的。最難的部分是決定要刪除哪些對象。下面是一些示例代碼靶向iTextSharp的4.1.6，首先創建一個帶有兩個矩形組成的PDF，然後創建基於第一移除了矩形之一的第二PDF。你需要運用你的邏輯來找出你想要刪除的矩形。有可能你實際上沒有矩形，而是直線形成一個矩形，在這種情況下，你也需要修改一下代碼。

這第一位剛在桌面上創建一個基本的PDF與兩個矩形：

//Create a file on the desktop with two rectangles 
var file1 = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "File1.pdf"); 
using (var fs = new FileStream(file1, FileMode.Create, FileAccess.Write, FileShare.None)) { 
    var doc = new Document(); 
    var writer = PdfWriter.GetInstance(doc, fs); 
    doc.Open(); 

    var cb = writer.DirectContent; 

    //Draw two rectangles 
    cb.SaveState(); 
    cb.SetColorStroke(iTextSharp.text.Color.RED); 
    cb.Rectangle(40, 60, 200, 100); 
    cb.Stroke(); 
    cb.RestoreState(); 

    cb.SaveState(); 
    cb.SetColorStroke(iTextSharp.text.Color.BLUE); 
    cb.Rectangle(500, 80, 90, 50); 
    cb.Stroke(); 
    cb.RestoreState(); 

    doc.Close(); 
} 

接下來的這個部分是更加複雜的部分。我鼓勵你做一個Console.WriteLine(tokenizer.StringValue);內while循環的看到所有的PDF命令。你會注意到他們使用RPN syntax這可能需要一點時間才能使用。有關更多問題，請參閱代碼中的註釋。

//Bind a reader to our first file 
var reader = new PdfReader(file1); 
//Get the first page (this would normally be done in a loop) 
var page = reader.GetPageN(1); 
//Get the "contents" of that page 
var objectReference = (PdfIndirectReference)page.Get(PdfName.CONTENTS); 
//Get the actual stream of the "contents" 
var stream = (PRStream)PdfReader.GetPdfObject(objectReference); 
//Get the raw bytes of the stream 
var streamBytes = PdfReader.GetStreamBytes(stream); 
//Convert the bytes to actual PDF tokens/commands 
var tokenizer = new PRTokeniser(new RandomAccessFileOrArray(streamBytes)); 
//We're going to re-append each token to this below buffer and remove the ones that we don't want 
List<string> newBuf = new List<string>(); 
//Loop through each PDf token 
while (tokenizer.NextToken()) { 
    //Add them to our master buffer 
    newBuf.Add(tokenizer.StringValue); 
    //The "Other" token is used for most commands, so if we're on "Other" and the current command is "re" which is rectangle 
    if (
     tokenizer.TokenType == PRTokeniser.TK_OTHER && //The "Other" token is used for most commands 
     newBuf[newBuf.Count - 1] == "re" &&   //re is the rectangle command 
     newBuf[newBuf.Count - 5] == "40"    //PDFs use RPN syntax so the red rectangle command was "40 60 200 100 re" 
     ) { 
     newBuf.RemoveRange(newBuf.Count - 5, 5);  //If the above conditions were met remove the last 5 commands 
    } 
} 

//Convert our array to a string with newlines between each token, convert that to an ASCII byte array and push that back into the stream (erasing the current contents) 
stream.SetData(System.Text.Encoding.ASCII.GetBytes(String.Join("\n", newBuf.ToArray()))); 

//Create a new file with the rectangle removed 
var file2 = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "File2.pdf"); 
using (var fs = new FileStream(file2, FileMode.Create, FileAccess.Write, FileShare.None)) { 
    //Bind a stamper to our read above which has the altered stream 
    var stamper = new PdfStamper(reader, fs); 
    //Loop through each page 
    int total = reader.NumberOfPages; 
    for (int i = 1; i <= total; i++) { 
     //Push the content over page by page 
     reader.SetPageContent(i, reader.GetPageContent(i)); 
    } 
    stamper.Close(); 
} 
reader.Close();