Rotating stamp about the center point

Aspose.Pdf.Facades namespace in Aspose.PDF for .NET allows you to add a stamp in an existing PDF file. Sometimes, users do need to rotate the stamp. In this article, we’ll see how to rotate a stamp about its center point.

Implementation details

Stamp class allows you to add a watermark in a PDF file. You can specify image to be added as a stamp using BindImage method. The SetOrigin method allows you to set the origin of the added stamp; this origin is the lower-left coordinates of the stamp. You can also set the size of the image using SetImageSize method.

Now, we see how the stamp can be rotated about the center of the stamp. Stamp class provides a property named Rotation. This property sets or gets the rotation from 0 to 360 of stamp content. We can specify any rotation value from 0 to 360. By specifying the rotation value we can rotate the stamp about its center point. If a Stamp is an object of Stamp type then the rotation value can be specified as aStamp.Rotation = 90. In this case the stamp will be rotated at 90 degrees about the center of the stamp content. The following code snippet shows you how to rotate the stamp about the center point:

private static void AddRotatingStampToPdf()
{
    var dataDir = RunExamples.GetDataDir_AsposePdfFacades_TechnicalArticles();  // Using dynamic path

    // Set path of the image to be set as watermark
    string imageFile = dataDir + "RotatingStamp.jpg";

    // Set input file path
    string inFile = dataDir + "RotatingStamp.pdf";

    // Set output file path
    string outFile = dataDir + "RotatingStamp_out.pdf";  // Output file with '_out' suffix

    // Create PdfFileInfo object to get height and width of the pages
    using (var fileInfo = new Aspose.Pdf.Facades.PdfFileInfo(inFile))
    {
        // Create Stamp object
        var aStamp = new Aspose.Pdf.Facades.Stamp();

        // Bind image file with the Stamp object
        aStamp.BindImage(imageFile);

        // Specify whether the stamp will be added as a background or not
        aStamp.IsBackground = false;

        // Specifies at which pages to add the watermark
        aStamp.Pages = new int[] { 1 };

        // Specifies the watermark rotation - rotate at 90 degrees
        aStamp.Rotation = 90;

        // Specifies the position of stamp - lower left corner of the stamp
        aStamp.SetOrigin(fileInfo.GetPageWidth(1) / 2, fileInfo.GetPageHeight(1) / 2);

        // Set the size of the watermark
        aStamp.SetImageSize(100, 100);

        // Create a Document object for the input PDF
        using (var doc = new Aspose.Pdf.Document(inFile))
        {
            // Create PdfFileStamp class to bind input and output files
            using (var stamper = new Aspose.Pdf.Facades.PdfFileStamp(doc))
            {
                // Add the stamp in the PDF file
                stamper.AddStamp(aStamp);
            }
        }
    }
}