How do I programmatically apply redaction annotations using the SDK?

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Shakthi Wijeratne

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Aug 20, 2020, 2:51:25 PM8/20/20
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Question:
I am using WebViewer / Adobe Reader to add redaction annotations to a PDF. How can I apply these annotations (and redact the document) in code?

Answer:
The following C# code will iterate through the document and apply all redaction annotations. Note that once the document is redacted, the redaction annotations will also be removed.

static Rect QuadPointToRect(QuadPoint qp)
{
    double rectX1 = Math.Min(Math.Min(Math.Min(qp.p1.x, qp.p2.x), qp.p3.x), qp.p4.x);
    double rectX2 = Math.Max(Math.Max(Math.Max(qp.p1.x, qp.p2.x), qp.p3.x), qp.p4.x);
    double rectY1 = Math.Min(Math.Min(Math.Min(qp.p1.y, qp.p2.y), qp.p3.y), qp.p4.y);
    double rectY2 = Math.Max(Math.Max(Math.Max(qp.p1.y, qp.p2.y), qp.p3.y), qp.p4.y);
   
    return new Rect(rectX1, rectY1, rectX2, rectY2);
}


static void RedactDoc(PDFDoc doc)
{
    ArrayList rarr = new ArrayList();

    for (PageIterator itr = doc.GetPageIterator(); itr.HasNext(); itr.Next())
    {
        Page page = itr.Current();
        int num_annots = page.GetNumAnnots();
        for (int i = 0; i < num_annots; ++i)
        {
            Annot annot = page.GetAnnot(i);
            if (!annot.IsValid()) continue;
            switch (annot.GetType())
            {
                case Annot.Type.e_Redact:
                    {
                        var redact = new pdftron.PDF.Annots.Redaction(annot);                             
                        var quadPointCount = redact.GetQuadPointCount();
                        if (quadPointCount != 0)
                        {
                            for (int j=0; j<quadPointCount; j++ )
                            {
                                var initialRect = QuadPointToRect(redact.GetQuadPoint(j));
                                var redaction = new Redactor.Redaction(page.GetIndex(), initialRect, false, redact.GetOverlayText());
                                rarr.Add(redaction);
                            }
                        } else
                        {
                            var redaction = new Redactor.Redaction(page.GetIndex(), redact.GetRect(), false, redact.GetOverlayText());
                            rarr.Add(redaction);
                        }
                        break;
                    }
                default:
                    break;
            }
        }
    }

    Redactor.Appearance app = new Redactor.Appearance();
    app.RedactionOverlay = true;
    app.Border = true;
    app.ShowRedactedContentRegions = true;

    Redactor.Redact(doc, rarr, app, false, true);
}

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