Ref:

ASP.Net: Convert Text String to Image using C# and VB.Net

Please refer this code

HTML

<asp:TextBox runat = "server" ID = "txtText"></asp:TextBox>
<asp:Button ID = "btnConvert" runat = "server" Text = "Convert" 
    onclick="btnConvert_Click" />
<hr />
<asp:Image ID = "imgText" runat = "server" Visible = "false" />

 Namespaces

using System.Drawing.Text;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Drawing.Imaging;

protected void btnConvert_Click(object sender, EventArgs e)
{
    string text = "I am going to home";
    string[] splitedText = text.Split(' ');
    string firstString = string.Join(" ", splitedText[0], splitedText[1]);
    string secondString = splitedText[2];
    string thirdString = string.Join(" ", splitedText[3], splitedText[4]);
    Bitmap bitmap = new Bitmap(1, 1);
    Font font = new Font("Arial", 25, FontStyle.Regular, GraphicsUnit.Pixel);
    Graphics graphics = Graphics.FromImage(bitmap);
    int width = (int)graphics.MeasureString(text, font).Width;
    int height = (int)graphics.MeasureString(text, font).Height;
    bitmap = new Bitmap(bitmap, new Size(width, height));
    graphics = Graphics.FromImage(bitmap);
    graphics.Clear(Color.White);
    graphics.SmoothingMode = SmoothingMode.AntiAlias;
    graphics.TextRenderingHint = TextRenderingHint.AntiAlias;
    graphics.DrawString(firstString, font, new SolidBrush(Color.FromArgb(0, 0, 255)), 0, 0);
    graphics.DrawString(secondString, font, new SolidBrush(Color.FromArgb(255, 0, 0)), 60, 0);
    graphics.DrawString(thirdString, font, new SolidBrush(Color.FromArgb(0, 255, 0)), 130, 0);
    graphics.Flush();
    graphics.Dispose();
    string fileName = Path.GetFileNameWithoutExtension(Path.GetRandomFileName()) + ".jpg";
    bitmap.Save(Server.MapPath("~/images/") + fileName, ImageFormat.Jpeg);
    imgText.ImageUrl = "~/images/" + fileName;
    imgText.Visible = true;
}

Screenshot