Question

我在LibreOffice中创建了一个PDF模板，我正在使用AcroFields填充它。在一些罕见的情况下，我想隐藏一个特定的字段，因此我使用RemoveField方法删除它。然而它的边界仍留在那里。从我用Google搜索的内容来看，它似乎可能是LibreOffice创建表单的方式。

到目前为止，我想到的是得到场的矩形并用白色图像覆盖它。问题是，客户计划使用背景图像和/或其他背景颜色创建模板而非白色使我当前的解决方案几乎无法使用

因此问题是 - 是否有某种方法可以删除边界？ [例如。通过访问ITextSharp的一些低级对象模型，或类似的东西]

提前多多感谢

Answer 1

删除单个绘图对象可能会有点棘手但并非不可能。最难的部分是决定要删除的对象。下面是一些针对iTextSharp 4.1.6的示例代码，它首先创建一个带有两个矩形的PDF，然后根据第一个PDF删除其中一个矩形创建第二个PDF。您需要应用逻辑来确定要删除的矩形。可能你实际上没有矩形但是恰好形成矩形的线条，在这种情况下你也需要稍微修改一下代码。

这第一位只是在桌面上创建一个带有两个矩形的基本PDF：

//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();
}

下一部分是更复杂的部分。我鼓励您在Console.WriteLine(tokenizer.StringValue);循环内部执行while以查看所有PDF命令。您会注意到他们使用的RPN syntax可能需要一点点使用。有关更多问题，请参阅代码中的注释。

//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();

ITextSharp 4.1.6 - 从PDF模板中删除现有行

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