Tarık Akbay

Basit kullanımlı, basit bir captcha ihtiyacımı karşılamak için geliştirdiğim kod blokları aşağıda ki gibidir.

Razor olarak kullanmak için Html Extensions

    public static partial class HtmlExtensions
    {
        public static MvcHtmlString Captcha(this HtmlHelper helper)
        {
            string result = string.Empty;

            var panel = new TagBuilder("div");
            panel.Attributes.Add("class", "panel panel-default");

            var mainDiv = new TagBuilder("div");
            mainDiv.Attributes.Add("id", "captchaHtmlExtensions");
            mainDiv.Attributes.Add("ct-captcha", "");

            var imageDiv = new TagBuilder("div");
            imageDiv.Attributes.Add("id", "captchaImage");
            imageDiv.Attributes.Add("class", "col-md-12");
            imageDiv.Attributes.Add("onclick", "getCaptchaImage()");

            var input = new TagBuilder("input");
            input.Attributes.Add("name", "captchaValue");
            input.Attributes.Add("id", "captchaValue");
            input.Attributes.Add("class", "form-control");
            input.Attributes.Add("type", "form-text");
            input.Attributes.Add("placeholder", "Kodu Giriniz");

            var text = new TagBuilder("h6");
            text.InnerHtml = "Doğrulama Kodu";
            text.Attributes.Add("class", "panel-heading panel-title");

            panel.InnerHtml += text.ToString();
            panel.InnerHtml += mainDiv.ToString();
            panel.InnerHtml += imageDiv.ToString();
            panel.InnerHtml += input.ToString();

            result += panel.ToString(TagRenderMode.Normal);

            return MvcHtmlString.Create(result);
        }
    }

base64 olarak geri dönen captcha image methodu:

        public static string GetCaptchaImageByBase64()
        {
            bool noisy = true;
            var random = new Random((int)DateTime.Now.Ticks);

            int imageWidth = 100;
            int imageHeight = 30;

            //generate text
            int length = 3;
            string characters = "ABCDEFGHIJKLMNOPRSTUVYZ";
            StringBuilder result = new StringBuilder(length);
            for (int i = 0; i < length; i++)
            {
                result.Append(characters[random.Next(characters.Length)]);
            }

            //generate text

            var captcha = result.ToString();

            //result
            HttpContext.Current.Session["CaptchaImageResult"] = result.ToString();

            //captchaImage

            using (var mem = new MemoryStream())
            using (var bmp = new Bitmap(imageWidth, imageHeight))
            using (var gfx = Graphics.FromImage((Image)bmp))
            {
                gfx.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
                gfx.SmoothingMode = SmoothingMode.AntiAlias;
                gfx.FillRectangle(Brushes.White, new Rectangle(0, 0, bmp.Width, bmp.Height));

                if (noisy)
                {
                    int i, r, x, y;
                    var pen = new Pen(Color.Yellow);
                    for (i = 1; i < 8; i++)
                    {
                        pen.Color = Color.FromArgb(
                        (random.Next(0, 255)),
                        (random.Next(0, 255)),
                        (random.Next(0, 255)));

                        r = random.Next(0, (imageWidth / 3));
                        x = random.Next(0, imageWidth);
                        y = random.Next(0, imageHeight);

                        gfx.DrawEllipse(pen, x - r, y - r, r, r);
                    }
                }

                //image add text
                gfx.DrawString(captcha, new Font("Tahoma", 18), Brushes.Gray, 15, 3);

                //generate image stream
                bmp.Save(mem, System.Drawing.Imaging.ImageFormat.Png);
                string srcValue = string.Format("data:image/png;base64, {0}", Convert.ToBase64String(mem.ToArray()));

                return srcValue;
            }
        }

Oluşan captcha image’nı json olarak döndüren method:

        public ActionResult GetCaptchaImageJson()
        {
            return Json(Operations.GetCaptchaImageByBase64(), JsonRequestBehavior.AllowGet);
        }

Javascript function:

$(document).ready(function () {
    $("div").each(function () {

        if ($(this).attr("ct-Captcha") != undefined) {
            getCaptchaImage();

            $("#captchaValue").bind('keyup', function (e) {
                if (e.which >= 97 && e.which <= 122) {
                    var newKey = e.which - 32;
                    e.keyCode = newKey;
                    e.charCode = newKey;
                }
                $("#captchaValue").val(($("#captchaValue").val()).toUpperCase());
            });
        }
    });
});
function getCaptchaImage() {
    $.ajax({
        cache: false,
        async: true, //!!!
        type: "POST",
        url: pureRoot + "Json/GetCaptchaImageJson",
        success: function (data) {
            //console.log(data, "UTIL -> getCaptchaImage -> success");
            $('#captchaImage').html('<div style="margin:5px;"><img src="' + data + '" class="img-responsive" title="Yenilemek için tıklayınız"/></div>')
            $("#captchaValue").val('');
        },
        error: function (xhr, ajaxOptions, thrownError) {
            console.log("Bağlantı sırasında hata oluştu!", "UTIL -> getCaptchaImage -> error");
        }
    });
}

Kullanımı:

@Html.Captcha()