展平后缺少注释（戳记）

Question

Annotation(PdfName.STAMP) 在被 itextsharp5.5.13.1 展平后丢失。 我有两个pdf。一个有效，另一个无效。 任何想法将不胜感激。

代码如下

string outFile = inputFile + "_f.pdf";
using (PdfReader pdfReader = new PdfReader(inputFileName))
{
    PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(outFile, FileMode.Create, FileAccess.Write, FileShare.None))

    //pdfStamper.FormFlattening = true;
    //pdfStamper.FreeTextFlattening = true;
    pdfStamper.AnnotationFlattening = true;
    //pdfStamper.AcroFields.GenerateAppearances = true;

}

Answer 1

原因是iTextSharp中的一个bug，如果其边界框不使用原点作为左下角，则注释展平无法正确计算展平注释的位置.

如果您查看PdfStamperImp.FlattenAnnotations(bool) 的代码，您会很快意识到if (app != null) 块中的计算仅在边界框位于原点或不需要缩放来拟合外观边界时才有意义框到注释矩形中。

（由于边界框的左下角通常是原点，因此不会经常弹出。）

因此，为了展平此类注释，您必须使用不同的展平方法，例如像这样：

using (PdfReader pdfReader = new PdfReader(inputFileName))
{
    PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(outFile, FileMode.Create, FileAccess.Write, FileShare.None));
    ImprovedAnnotationFlattening(pdfStamper);
    pdfStamper.Close();
}

使用这些辅助方法：

void ImprovedAnnotationFlattening(PdfStamper pdfStamper)
{
    double[] DEFAULT_MATRIX = { 1, 0, 0, 1, 0, 0 };

    PdfReader reader = pdfStamper.Reader;

    for (int page = 1; page <= reader.NumberOfPages; ++page)
    {
        PdfDictionary pageDic = reader.GetPageN(page);
        PdfArray annots = pageDic.GetAsArray(PdfName.ANNOTS);

        if (annots == null)
            continue;

        for (int idx = 0; idx < annots.Size; ++idx)
        {
            PdfObject annoto = annots.GetDirectObject(idx);
            if (!(annoto is PdfDictionary))
                continue;

            PdfDictionary annDic = (PdfDictionary)annoto;

            PdfNumber ff = annDic.GetAsNumber(PdfName.F);
            int flags = ff != null ? ff.IntValue : 0;
            if ((flags & PdfFormField.FLAGS_PRINT) == 0 || (flags & PdfFormField.FLAGS_HIDDEN) != 0)
                continue;

            PdfObject obj1 = annDic.Get(PdfName.AP);
            if (obj1 == null)
                continue;
            PdfDictionary appDic = obj1 is PdfIndirectReference
                ? (PdfDictionary)PdfReader.GetPdfObject(obj1)
                : (PdfDictionary)obj1;
            PdfObject obj = appDic.Get(PdfName.N);
            PdfStream objDict = appDic.GetAsStream(PdfName.N);

            if (objDict != null)
            {
                Rectangle rect = PdfReader.GetNormalizedRectangle(annDic.GetAsArray(PdfName.RECT));
                Rectangle bbox = PdfReader.GetNormalizedRectangle(objDict.GetAsArray(PdfName.BBOX));

                PdfContentByte cb = pdfStamper.GetOverContent(page);
                cb.SetLiteral("Q ");

                PdfArray matrixArray = objDict.GetAsArray(PdfName.MATRIX);
                double[] matrix = matrixArray != null ? matrixArray.AsDoubleArray() : DEFAULT_MATRIX;
                AffineTransform transform = new AffineTransform(matrix);

                double[] bboxCorners = { bbox.Left, bbox.Bottom, bbox.Right, bbox.Bottom, bbox.Right, bbox.Top, bbox.Left, bbox.Top };
                transform.Transform(bboxCorners, 0, bboxCorners, 0, 4);
                double minX = Min(bboxCorners, 0, 2);
                double maxX = Max(bboxCorners, 0, 2);
                double minY = Min(bboxCorners, 1, 2);
                double maxY = Max(bboxCorners, 1, 2);

                transform.preConcatenate(AffineTransform.GetTranslateInstance(-minX, -minY));
                transform.preConcatenate(AffineTransform.GetScaleInstance(rect.Width/(maxX-minX), rect.Height/(maxY-minY)));
                transform.preConcatenate(AffineTransform.GetTranslateInstance(rect.Left, rect.Bottom));

                transform.GetMatrix(matrix);

                cb.AddFormXObj(objDict, GenerateName(), matrix[0], matrix[1], matrix[2], matrix[3], matrix[4], matrix[5]);

                cb.SetLiteral("q ");

                annots.Remove(idx);
                --idx;
            }
        }
    }
}

double Min(double[] array, int start, int step)
{
    double result = array[start];

    for (int i = start + step; i < array.Length; i+=step)
    {
        result = Math.Min(result, array[i]);
    }

    return result;
}

double Max(double[] array, int start, int step)
{
    double result = array[start];

    for (int i = start + step; i < array.Length; i += step)
    {
        result = Math.Max(result, array[i]);
    }

    return result;
}

PdfName GenerateName()
{
    PdfName name = new PdfName("XXX" + formXObjectsCounter);
    ++formXObjectsCounter;
    return name;
}

int formXObjectsCounter = 4711;

注意：我刚刚编写了这些方法（尽可能多地从原始扁平化代码中复制），并且仅使用您的示例文件进行了测试。一些边界条件可能仍需考虑用于一般用途。特别是我没有做所有相关的null 或0 测试。我也没有尝试支持正确的标记。