How to Create Text Image on the fly with ASP.NET

Introduction

Have you ever wondered how to dynamically create a text image? Similar to those shown on Yahoo! Groups for manual verification whenever you want to join a new group? The code sample shows you how to do just that in ASP.NET, making use of Microsoft's GDI+ library.

I believe the code is quite easy to understand for those familiar with System.Drawing namespace, so I won't explain much. If you look at the online demo and examine the sample code below, I'm sure you'll pretty much grasp everything...

There may be other uses of generating text images, I'm not sure for what else, but I'm sure it's something that won't allow the user to copy-paste text!

The online demo is provided here.

...and here is the .aspx file for it (in C#):

<%@ Page Language="C#" trace="false" Explicit="true" aspcompat="true" Debug="true" %>
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Text" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<%@ Import Namespace="System.Drawing.Text" %>
<%@ Import Namespace="System.Drawing.Drawing2D" %>

<script runat="server">
//-------------------------------------

// fonter.net v1.0

//-------------------------------------

// Text Images On the Fly using ASP.Net

// Written in C# and GDI+ library

//-------------------------------------

// (C) Zeddy Iskandar, 2003-onwards.

// Provided as-is, author is not

// responsible for anything.

//------------------------------------- 


public void Page_Load(object sender, System.EventArgs e)
{
   if (Request.HttpMethod == "POST")
   {
    string text = Request.Form.Get("text");
    int textLength = text.Length;
    int fontSize = Convert.ToInt32(Request.Form.Get("fontsize"));
    int orientation = Convert.ToInt32(Request.Form.Get("orientation"));
    int antialias = Convert.ToInt32(Request.Form.Get("antialias")); 

    // Set canvas width & height

    int width; 
    int height;
    if (orientation == 1)
    {
     width  = (fontSize * textLength) - ((textLength * fontSize)/3);
     height = fontSize + 20;
    }
    else
    {
     width  = fontSize + 20;
     height = (int)(fontSize * textLength * 1.5);
    } 

    // Initialize graphics

    RectangleF rectF =new RectangleF(0, 0, width, height);
    Bitmap pic = new Bitmap(width, height, PixelFormat.Format24bppRgb);
    Graphics g = Graphics.FromImage(pic);
    g.SmoothingMode = SmoothingMode.AntiAlias;
    if (antialias == 1) g.TextRenderingHint = TextRenderingHint.AntiAlias; 

    // Set colors

    string fgColor = Request.Form.Get("fontcolor");
    string bgColor = Request.Form.Get("bgcolor");
    Color fontColor = Color.FromName(fgColor);
    Color rectColor = Color.FromName(bgColor);
    SolidBrush fgBrush = new SolidBrush(fontColor);
    SolidBrush bgBrush = new SolidBrush(rectColor); 

    // Rectangle or ellipse?

    int bound = Convert.ToInt32(Request.Form.Get("bound"));
    if (bound == 1)
    {
     g.FillRectangle(bgBrush, rectF);
    }
    else
    {
     g.FillRectangle(new SolidBrush(Color.White), rectF);
     g.FillEllipse(bgBrush, rectF);
    } 

    // Load font

    string fontName = Request.Form.Get("fontname") + ".ttf";
    PrivateFontCollection privateFontCollection = new PrivateFontCollection();
    privateFontCollection.AddFontFile(Server.MapPath("./") + fontName); 
    FontFamily fontFamily = privateFontCollection.Families[0]; 

    // Set font style

    int fontStyle = Convert.ToInt32(Request.Form.Get("fontstyle"));
    FontStyle style = FontStyle.Regular;
    switch (fontStyle)
    {
     case 2:
      style = FontStyle.Bold;
      break; 

     case 3:
      style = FontStyle.Italic;
      break; 

     case 4:
      style = (FontStyle.Bold) | (FontStyle.Italic);
      break; 

     case 5:
      style = FontStyle.Strikeout;
      break; 

     case 6:
      style = FontStyle.Underline;
      break;
    }
    Font font = new Font(fontFamily, fontSize, style, GraphicsUnit.Pixel); 

    // Set font direction & alignment

    StringFormat format = new StringFormat();
    int reverse = Convert.ToInt32(Request.Form.Get("reverse"));
    if (reverse == 1 && orientation == 1)
    {
     format.FormatFlags = StringFormatFlags.DirectionRightToLeft;
    }
    else if (reverse == 1 && orientation > 1)
    {
     StringBuilder temp = new StringBuilder();
     for (int i = textLength-1; i >= 0; i--)
     {
      temp.Insert((textLength-1) - i, text[i]);
     }
     text = temp.ToString();
    } 
    if (orientation > 1)
    {
     rectF.X = width/4;
     rectF.Width = fontSize - (fontSize/4);
    } 
    int alignment = Convert.ToInt32(Request.Form.Get("alignment"));
    if (alignment == 1)
    {
     format.Alignment = StringAlignment.Near;
    }
    else if (alignment == 2)
    {
     format.Alignment = StringAlignment.Center;
    }
    else
    {
     format.Alignment = StringAlignment.Far;
    }
    format.LineAlignment = StringAlignment.Center; 

    // Draw any drop-shadow

    int dropShadow = Convert.ToInt32(Request.Form.Get("dropshadow"));
    if (dropShadow > 0)
    {
     Color shadowColor = Color.FromName(Request.Form.Get("shadowcolor"));
     switch(dropShadow)
     {
      case 1:
       rectF.Offset(-3, -3);
       g.DrawString(text, font, new SolidBrush(shadowColor), rectF, format);
       rectF.Offset(+3, +3);
       break; 

      case 2:
       rectF.Offset(+3, -3);
       g.DrawString(text, font, new SolidBrush(shadowColor), rectF, format);
       rectF.Offset(-3, +3);
       break; 

      case 3:
       rectF.Offset(-3, +3);
       g.DrawString(text, font, new SolidBrush(shadowColor), rectF, format);
       rectF.Offset(+3, -3);
       break; 

      case 4:
       rectF.Offset(+3, +3);
       g.DrawString(text, font, new SolidBrush(shadowColor), rectF, format);
       rectF.Offset(-3, -3);
       break;
     }
    } 

    // Finally, draw the font

    g.DrawString(text, font, fgBrush, rectF, format); 
    Response.ContentType = "image/jpeg";
    pic.Save(Response.OutputStream, ImageFormat.Jpeg); 

    // Dispose objects

    pic.Dispose();
   }
   else
   {
    Response.ContentType = "text/html";
    Response.Write("<html><body>");
    Response.Write("fonter.net v1.0 <br> Create Text Images On-the-Fly <br>");
    Response.Write("(C)2003-onwards, Zeddy Iskandar");
    Response.Write("</body></html>");
   }
}
</script>