Ytukyg

I am trying to overlay two PDF files using iText7/C#.
The first one is kind of background and the second one is containing form fields.
Everything works fine and only problem is that I lose fonts from the second file.

I try as follows:

static public bool Overlay(string back_path, string front_path, string merge_path)

{

    PdfReader reader;

    PdfDocument pdf = null, front;

    try

    {

        reader = new PdfReader(back_path);

        pdf = new PdfDocument(reader, new PdfWriter(merge_path));

        front = new PdfDocument(new PdfReader(front_path));



        var form = PdfAcroForm.GetAcroForm(front, false);

        PdfAcroForm dform = PdfAcroForm.GetAcroForm(pdf, true);

        IDictionary<String, PdfFormField> fields = form.GetFormFields();



        // copy styles

        dform.SetDefaultResources(form.GetDefaultResources());

        dform.SetDefaultAppearance(form.GetDefaultAppearance().GetValue());



        // do overlay

        foreach (KeyValuePair<string, PdfFormField> pair in fields)

        {

            try

            {

                var field = pair.Value;

                PdfPage page = field.GetWidgets().First().GetPage();



                int pg_no = front.GetPageNumber(page);

                if (pg_no < front_start_page || pg_no > front_end_page)

                    continue;

                PdfObject copied = field.GetPdfObject().CopyTo(pdf, true);

                PdfFormField copiedField = PdfFormField.MakeFormField(copied, pdf);



                // The following returns null. If it returns something, I think I could use copiedField.setFont(font). 

                // var font = field.GetFont(); 



                dform.AddField(copiedField, pdf.GetPage(pg_no));

            }

            catch (Exception ex)

            {

                System.Diagnostics.Debug.WriteLine($"Overlaying field {pair.Key} failed. ({ex.Message})");

            }

        }



        pdf.Close();

        return true;

    }

    catch (Exception ex)

    {

        throw new OverlayException(ex.Message);

    }

}



public static PdfDictionary get_font_dict(PdfDocument pdfDoc)

{

    PdfDictionary acroForm = pdfDoc.GetCatalog().GetPdfObject().GetAsDictionary(PdfName.AcroForm);

    if (acroForm == null)

    {

        return null;

    }

    PdfDictionary dr = acroForm.GetAsDictionary(PdfName.DR);

    if (dr == null)

    {

        return null;

    }

    PdfDictionary font = dr.GetAsDictionary(PdfName.Font);

    return font;

}

So basically I get all fonts from the second PDF and copy them to the final PDF.
But it does not work.

Logically, I think setting font of the original field to the copied one is the right way.
I mean PdfFormField.GetFont() and SetFont().
But it always returns null.

In a comment you clarified:

the background PDF can be assumed not to have form fields or annotations. I mean we can assume background PDF only contains static content (scanned form) and the front PDF only contains formfields.

In that case the easiest way to implement your method is to add the background as xobject to the form PDF instead of adding the form to the background PDF.

You can simply do that like this:

PdfReader formReader = new PdfReader(front_path);

PdfReader backReader = new PdfReader(back_path);

PdfWriter writer = new PdfWriter(merge_path);



using (PdfDocument source = new PdfDocument(backReader))

using (PdfDocument target = new PdfDocument(formReader, writer))

{

    PdfFormXObject xobject = source.GetPage(1).CopyAsFormXObject(target);

    PdfPage targetFirstPage = target.GetFirstPage();

    PdfStream stream = targetFirstPage.NewContentStreamBefore();

    PdfCanvas pdfCanvas = new PdfCanvas(stream, targetFirstPage.GetResources(), target);

    Rectangle cropBox = targetFirstPage.GetCropBox();

    pdfCanvas.AddXObject(xobject, cropBox.GetX(), cropBox.GetY());

}

Depending on the exact static contents of the background and the form PDF, you might want to use NewContentStreamAfter instead of NewContentStreamBefore or even to use some nifty blend mode to get the exact static content look you want.