使用iTextSharp填写其他字段时,如何强制PDF格式化和计算？

using (PdfReader pdfReader = new PdfReader(inputFile))
{
    using (PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(outputFile, FileMode.Create)))
    {
        AcroFields pdfFormFields = pdfStamper.AcroFields;
        pdfFormFields.SetField("fieldName", "fieldValue");
        pdfStamper.FormFlattening = true;
    }
}

using (PdfReader pdfReader = new PdfReader(inputFile))
{
    using (PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(outputFile, FileMode.Create)))
    {
        AcroFields pdfFormFields = pdfStamper.AcroFields;
        pdfFormFields.SetField("fieldName", "fieldValue");
        PdfFormField field = pdfFormFields.GetFieldItem("fieldName");
        field.SetFieldFlags(PdfFormField.FF_READ_ONLY);
    }
}

using (PdfReader pdfReader = new PdfReader(inputFile))
{
    using (PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(outputFile, FileMode.Create)))
    {
        AcroFields pdfFormFields = pdfStamper.AcroFields;
        pdfFormFields.SetField("fieldName", "fieldValue");
        PdfFormField field = pdfFormFields.GetFieldItem("fieldName");
        PdfDictionary widget = field.GetWidget(0);
        PdfArray bBox = widget.GetAsArray(PdfName.RECT);
        float x1 = bBox.GetAsNumber(0).FloatValue;
        float y1 = bBox.GetAsNumber(1).FloatValue;
        float x2 = bBox.GetAsNumber(2).FloatValue;
        float y2 = bBox.GetAsNumber(3).FloatValue;
        PdfContentByte canvas = pdfStamper.GetOverContent(widget.GetAsNumber(PdfName.PAGE).IntValue);
        canvas.SetColorStroke(BaseColor.BLACK);
        canvas.Rectangle(x1, y1, x2 - x1, y2 - y1);
        canvas.Stroke();
    }
}