custom.cs

using System;
using System.Drawing;
using System.IO;
using System.Text;
using System.Xml;
using TXTextControl;

public static class SignatureBoxManager
{
    public static string AddSignatureBox(TextControl textControl, Size size, int page, SignatureLocation signatureLocation, SignerData signerData, SignatureStyle signatureStyle)
    {
        SignatureField field = new SignatureField(size, "sign1", 1);
        field.SignerData = signerData;

        var pageBounds = textControl.GetPages()[1].TextBounds;

        var frameLocation = GetFrameLocation(signatureLocation, size, pageBounds);

        textControl.SignatureFields.Add(field, 1, frameLocation, FrameInsertionMode.AboveTheText);

        var stamp = Encoding.ASCII.GetBytes(GetSvgFromImage(size, signatureStyle.SvgImage, signerData, DateTime.Now.ToString(signatureStyle.DateFormat), signatureStyle));

        using (MemoryStream ms = new MemoryStream(stamp, 0, stamp.Length, writable: false, publiclyVisible: true))
        {
            field.Image = new SignatureImage(ms);
        }

        return field.Name;
    }

    private static Point GetFrameLocation(SignatureLocation location, Size size, Rectangle pageBounds)
    {
        switch (location)
        {
            case SignatureLocation.TopRight:
                return new Point(pageBounds.Right - size.Width, pageBounds.Top - 1440);
            case SignatureLocation.BottomLeft:
                return new Point(pageBounds.Left, pageBounds.Bottom - size.Height);
            case SignatureLocation.BottomRight:
                return new Point(pageBounds.Right - size.Width, pageBounds.Bottom - size.Height);
            default:
                return new Point(pageBounds.Left, pageBounds.Top - 1440);
        }
    }

    private static string GetSvgFromImage(Size size, string svgImage, SignerData signerData, string date, SignatureStyle style)
    {
        var sizeInPixels = new Size(size.Width / 15, size.Height / 15);
        var imageWidth = sizeInPixels.Width / 2;
        var fontSize = sizeInPixels.Width / 20;

        var signature = new Signature(svgImage, sizeInPixels);

        var svg = new StringBuilder();
        svg.Append("<svg xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" width=\"");
        svg.Append(sizeInPixels.Width);
        svg.Append("\" height=\"");
        svg.Append(sizeInPixels.Height);
        svg.Append("\">");

        svg.Append("<g transform=\"scale(" + signature.ScalingFactor / 2 + ") translate(0 0)\"");
        svg.Append(">");
        svg.Append(svgImage);
        svg.Append("</g>");

        var textPositions = new[] { fontSize, fontSize * 2, fontSize * 3, fontSize * 4 };

        foreach (var position in textPositions)
        {
            svg.Append($"<text x=\"{sizeInPixels.Width / 2}\" y=\"{position}\" font-family=\"{style.DetailsFont.FontFamily.Name}\" font-size=\"{fontSize}\" fill=\"red\">");
            if (position == fontSize)
                svg.Append("Digitally signed by");
            else if (position == fontSize * 2)
                svg.Append(signerData.Name);
            else if (position == fontSize * 3)
                svg.Append(signerData.Address);
            else if (position == fontSize * 4)
                svg.Append(date);
            svg.Append("</text>");
        }

        svg.Append("</svg>");
        return svg.ToString();
    }
}

public enum SignatureLocation
{
    TopLeft,
    TopRight,
    BottomLeft,
    BottomRight
}

public class SignatureStyle
{
    public SignatureStyle() { }
    public string SvgImage { get; set; }
    public bool ShowDate { get; set; } = true;
    public bool ShowLocation { get; set; } = true;
    public string DateFormat { get; set; } = "MM/dd/yyyy";
    public Font DetailsFont { get; set; } = new Font("Arial", 12);
}

internal class Signature
{

    private Size m_size;
    private Size m_distinationSize;
    private string m_signatureSVG;
    private float m_scalingFactor = 1.0f;

    public Signature(string signatureSVG, Size destinationSize)
    {
        m_signatureSVG = signatureSVG;
        m_distinationSize = destinationSize;
        m_size = GetSignatureSize();
        m_scalingFactor = CalculateScaling();
    }

    public Size Size { get { return m_size; } }
    public float ScalingFactor { get { return m_scalingFactor; } }

    private Size GetSignatureSize()
    {
        XmlDocument input = new XmlDocument();
        input.LoadXml(m_signatureSVG);
        XmlNodeList childNodes = input.GetElementsByTagName("svg");

        // find width or viewbox
        if (childNodes[0].Attributes["width"] != null)
        {
            return new Size(
                int.Parse(childNodes[0].Attributes["width"].Value),
                int.Parse(childNodes[0].Attributes["height"].Value));
        }
        else if (childNodes[0].Attributes["viewBox"] != null)
        {
            var viewBox = childNodes[0].Attributes["viewBox"].Value.Split(' ');
            return new Size(
                int.Parse(viewBox[2]),
                int.Parse(viewBox[3]));
        }

        return new Size(100, 100);
    }

    private float CalculateScaling()
    {

        float scalingFactor = 1;

        if (m_size.Width > m_distinationSize.Width)
        {
            scalingFactor = (float)m_distinationSize.Width / (float)m_size.Width;
        }

        return scalingFactor;
    }
}