Drawing on PDF using ITextSharp, without creating a new PDF

Question

i try to draw simple shapes (rectangles, circles..) on an existing PDF using ITextSharp, without having to create a new PDF. I found a post who talk about this issue (itextsharp modify existing pdf (no new source pdf) and add watermark) and i would like to know if anybody could tell me more about it.

my aim is to modify a pdf by adding a circle on it, the current solution involve the creation of a new PDF (Itextsharp). Is it possible to add a circle on a PDF without creating a new one ? Thank you.

J.

Answer 1

You can't read a file and write to it simultaneously. Think of how Word works: you can't open a Word document and write directly to it. Word always creates a temporary file, writes the changes to it, then replaces the original file with it and then throws away the temporary file.

You can do that too:

• read the original file with PdfReader,
• create a temporary file for PdfStamper, and when you're done,
• replace the original file with the temporary file.

Or:

• read the original file into a byte[],
• create PdfReader with this byte[], and
• use the path to the original file for PdfStamper.

This second option is more dangerous, as you'll lose the original file if you do something that causes an exception in PdfStamper.

As for adding content with PdfStamper, please take a look at the section entitled "Manipulating existing PDFs" in the free ebook The Best iText Questions on StackOverflow. You'll find questions such as:

• How to add a watermark to a PDF file?
• How do I insert a hyperlink to another page with iTextSharp in an existing PDF?
• iText - How to stamp image on existing PDF and create an anchor
• ...

All of these examples add content by creating a PdfContentByte instance like this:

PdfContentByte canvas = stamper.getOverContent(pagenumber);

It's this canvas you need to use when drawing a circle on the page with page number pagenumber. It is important that you use the correct coordinates when you do this. That's explained here: How to position text relative to page using iText?

Update:

Json posted the following code in the comments:

string oldFile = @"C:\Users\ae40394\Desktop\hello.pdf";
string newFile = @"C:\Users\ae40394\Desktop\NEW.pdf";
// creating a reader with the original PDF
PdfReader reader = new PdfReader(oldFile);
Rectangle rect = reader.GetPageSize(1);
FileStream fs = new FileStream(newFile,FileMode.Create);
using (PdfStamper stamper = new PdfStamper(reader, fs)) {
    // modify the pdf content
    PdfContentByte cb = stamper.GetOverContent(1);
    cb.SetColorStroke(iTextSharp.text.BaseColor.GREEN);
    cb.SetLineWidth(5f);
    cb.Circle(rect.GetLeft() + 30, rect.GetBottom() + 30 ,20f);
    cb.Stroke();
}    
reader.Close();
File.Replace(@"C:\Users\ae40394\Desktop\NEW.pdf", @"C:\Users\ae40394\Desktop\hello.pdf", @"C:\Users\ae40394\Desktop\hello.pdf.bac"); 

I slightly adapted the code, because:

• There is no need for a Document object,
• The stamper is closed when using is closed,
• When the stamper is closed, so is the FileStream
• the coordinates of the circle were hard coded. I used the page size to make sure they are made relative to the origin of the coordinate system, although to be sure, you may also want to check if there's a Crop Box.

Answer 2

You CAN read a file and write to it simultaneously.

Here is an example:

private void button4_Click(object sender, EventArgs e) 
{ 
    using (PdfReader pdfReader = new PdfReader(new FileStream(pdfInput, FileMode.Open, FileAccess.Read, FileShare.Read))) 
    { 
        using (PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(pdfInput, FileMode.Open, FileAccess.Write, FileShare.None))) 
        { 
            PdfContentByte canvas = pdfStamper.GetUnderContent(1); 
            canvas.SetColorFill(BaseColor.YELLOW); 
            canvas.Rectangle(36, 786, 66, 16); 
            canvas.Fill(); 
        } 
    } 
    // PDF Datei im Anschluss anzeigen/öffnen 
    System.Diagnostics.Process.Start(pdfInput); 
} 

Answer 3

string oldFile = @"C:\...6166-21.pdf";
        string newFile = @"C:\...NEW.pdf";

        // open the reader
        PdfReader reader = new PdfReader(oldFile);
        Rectangle size = reader.GetPageSizeWithRotation(1);
        Document document = new Document(size);

        FileStream fs = new FileStream(newFile, FileMode.Create, FileAccess.Write);
        PdfWriter writer = PdfWriter.GetInstance(document, fs);
        document.Open();

        // the pdf content
        PdfContentByte cb = writer.DirectContent;

        cb.SetColorStroke(iTextSharp.text.BaseColor.GREEN);
        cb.Circle(150f, 150f, 50f);
        cb.Stroke();

        // create the new page and add it to the pdf
        PdfImportedPage page = writer.GetImportedPage(reader, 1);
        cb.AddTemplate(page, 0, 0);

        // close the streams and voilá the file should be changed :)
        document.Close();
        fs.Close();
        writer.Close();
        reader.Close();