.NET とAIでスパムボットに対抗する（4）

[WebMethod(Description="Get an Word from OGDEN’s dictionary")]
public String selectWord ()

[WebMethod(Description="Generates a CAPTCHA Image and returns filename")]
public String generateImage ()

[WebMethod(Description="Returns a CAPTCHA Image in Base64-Encoding")]
publicbyte[] getCaptcha() 

wsdl /l:cs /o:captchaWebService.cs http://localhost/captchawebservice/captchaWebService.asmx?WSDL
     /n:captchaWebService
csc /out:captchaWebService.dll /t:library /r:system.web.dll,system.xml.dll,system.web.services.dll
     captchaWebService.cs

<%@ Page Language="c#" debug="True" %>
<%@ Import namespace="captchaWebService" %>
<script language="c#" runat="server">
publicvoid Page_Load(System.Object sender,System.EventArgs e)
{
Page.Response.BinaryWrite(new captchaWebService().getCaptcha());
}
</script>

<%@ webservice class="captchaWebService" language="c#" %>
using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Web;
using System.Web.Services;
using System.IO;
using System.Data.OleDb;
using System.Drawing;
using System.Drawing.Imaging;
    ///<summary>
    /// This is the basic Service for CAPTCHA provision.
    ///</summary>
    
[WebService(Namespace="http://axisebusiness.com/webservices/")]
publicclass captchaWebService : System.Web.Services.WebService
{
    [WebMethod(Description="Returns a CAPTCHA Image in Base64-Encoding")]
    publicbyte[] getCaptcha() 
    {
        return getBytesFromRaster(Server.MapPath(generateImage()));
    }
    
    // Returns byte from Image file
    
    publicbyte[] getBytesFromRaster(string filename) 
    {            
        if(File.Exists(filename)) 
        {
            try
            {
                FileStream s =File.OpenRead(filename);
                byte[] bytes = newbyte[s.Length];
                s.Read(bytes, (int)0, (int)s.Length);
                return bytes;
            } 
            catch(Exception e) 
            {
                returnnewbyte[0];
            }
        } 
        else
        {
            returnnewbyte[0];
        }
    }
    
    [WebMethod(Description="Generates a CAPTCHA Image and returns filename")]
    public String generateImage ()
    {
        //Reading the parameter from session this time
        String strText = selectWord ();// = Session("param") 
        //Create the memory map 
        Bitmap raster;
        System.Drawing.Imaging.PixelFormat pixFormat = 
            System.Drawing.Imaging.PixelFormat.Format32bppArgb;
        // Select an memory image from file of 290x80px
        // in the backgrounds folder named backX.jpg
        Graphics graphicsObject;
        System.Drawing.Image imageObject = 
            System.Drawing.Image.FromFile(Server.MapPath(@"backgroundsack" + 
            new Random().Next(9) + ".jpg"));
        // Creating the raster image object
        raster = new Bitmap (imageObject);
        //Creating graphics object
        graphicsObject = Graphics.FromImage(raster);
        // Instantiate object of brush with black color
        SolidBrush objBrush = new SolidBrush(Color.Black);
        Font objFont;
        int a;
        String myFont, str;
        //Creating an array for most readable yet cryptic fonts for OCR’s
        // This is entirely up to developer’s discretion
        String[] crypticFonts = new String[11];
        crypticFonts [0] = "Arial";
        crypticFonts [1] = "Verdana";
        crypticFonts [2] = "Comic Sans MS";
        crypticFonts [3] = "Impact";
        crypticFonts [4] = "Haettenschweiler";
        crypticFonts [5] = "Lucida Sans Unicode";
        crypticFonts [6] = "Garamond";
        crypticFonts [7] = "Courier New";
        crypticFonts [8] = "Book Antiqua";
        crypticFonts [9] = "Arial Narrow";
        crypticFonts [10] = "Estrangelo Edessa";
        //Loop to write the characters on image
        // with different fonts.
        for (a=0; a<=strText.Length-1; a++)
        {
            myFont = crypticFonts[new Random().Next(a)];
            objFont = new Font(myFont, 20, FontStyle.Bold);
            str = strText.Substring(a, 1);
            graphicsObject.DrawString(str, objFont, objBrush, a*20, 35);
            graphicsObject.Flush();
        }
        String filename= new Random().Next().ToString() + ".gif";
        raster.Save(Server.MapPath(filename), System.Drawing.Imaging.ImageFormat.Gif);
        raster.Dispose();
        graphicsObject=null;
        return filename;
    
    } // End of Function
    // *************************************
    // Select word web method
    // Return type String of random word from dictionary
    // Dictionary is based on OGDEN’s BASIC ENGLISH 
    // http://ogden.basic-english.org/basiceng.html
    [WebMethod(Description="Get an Word from OGDEN’s dictionary")]
    public String selectWord () 
    {
        
        // The Connection string referencing the MDB file
        String ConnectionString = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" 
            + Server.MapPath("dictionary.mdb") + ";";
        
        // Datareader object
        OleDbDataReader objReader;
        
        // Creating an array of 26 characters (alphabets in dictionary database as columns)
        char[] columns = newchar[26];
        
        // Adding the column names in the array
        // uses the ASCII character conversion for selecting values
        // from A- Z
        for (int a=65; a<65+26; a++)
            columns[a-65] = (char)a;
                
        // Query String for selecting a random column from spelling list database
        String QuerySQL = "SELECT " + columns[(new Random().Next(26))] + 
            " FROM spellList";
        // Opening the connection
        OleDbConnection objConn = new OleDbConnection(ConnectionString);
        // Creating new command object
        OleDbCommand objCmd = new OleDbCommand();
        // Assigning command text
        objCmd.CommandText = QuerySQL;
        // Assigning the connection to command object connection attribute
        objCmd.Connection = objConn;
        // Instantiating a random class object 
        Random randomSeed = new Random();
        // Creating a random seed selector
        int randomSeedSelector=0;
        // An string character with maximum capacity for dictionary column
        String[] selectedIndex = new String[700];
        String str = "";
        // This code segment opens the connection and read the dictionary
        try
        {
            objConn.Open();
            objReader = objCmd.ExecuteReader();
            while (objReader.Read()) 
            {
                str = objReader.GetValue(0).ToString();
                if (str.Length != 0) 
                {
                    selectedIndex[randomSeedSelector] =str;
                    randomSeedSelector++;
                }
            }// Ends While
            str = selectedIndex[randomSeed.Next(randomSeedSelector)];
            
        } // Ends Try
        catch (Exception Err)
        {
            // The Error Catching operations
        }
        finally
        {
            objConn.Close();
        }
        // Returns the selected string
        return (str);    
    }// ends web method
} // Ends Class