ค้นหาลายเซ็น Barcode ใน Pdf file

// Set up input Pdf file
string filePath = "input.pdf";

// Instantiate Signature for input file
using (var signature = new GroupDocs.Signature.Signature(filePath))
{
        //Create search options
        BarcodeSearchOptions options = new BarcodeSearchOptions()
        {
            // specify special pages to search on 
            AllPages = false,
            // single page number
            PageNumber = 1,
            // set up text match type
            MatchType = TextMatchType.Contains,
            // specify text pattern to search
            Text = "Text signature",
            // return  Barcode images for processing
            ReturnContent = true,
            // set up type of returned  Barcode images
            ReturnContentType = FileType.PNG
        };

        // search for Barcode signatures in Pdf document
        List<BarcodeSignature> signatures = signature.Search<BarcodeSignature>(options);

        // process signatures which were found                
        foreach (BarcodeSignature item in signatures)
        {
            //...
        }
}