High Quality Thumbnail Generator At Runtime Using ASP.NET And C#

Welcome to my first post.
I have coded a class to generate High quality thumbnails at runtime and also cache these images.

This class “Images.cs” is inherited by IHttpHandler so that this can be used as Handler to serve thumbnails. Thumbnail Width and Height is passed to handler using QueryString parameters.

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Web;
using System.IO;

namespace Xpertz.Base.Handler
{
    public class Images : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {

            var file = context.Request.FilePath.Replace(".ashx", String.Empty);
            var fileName = file.Substring(file.LastIndexOf('/') + 1);
            var extension = file.Substring(file.LastIndexOf('.'));

            int width;
            int height;
            int.TryParse(context.Request["w"], out width);
            int.TryParse(context.Request["h"], out height);

            var path = context.Server.MapPath(file);
            if (!File.Exists(path))
            {
                context.Response.StatusCode = 404;
                context.Response.End();
                return;
            }
            context.Response.Clear();
            context.Response.Cache.SetExpires(DateTime.Now.AddDays(10));
            context.Response.Cache.SetCacheability(HttpCacheability.Public);
            context.Response.Cache.SetValidUntilExpires(false);
            context.Response.AddHeader("content-disposition", "inline;filename=" + fileName);

            using (var fs = new FileStream(path,
                FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                using (var img = new Bitmap(fs))
                {
                    using (var ms = new MemoryStream())
                    {
                        Bitmap bmpOut = null;

                        if (width > 0 && height == 0)
                        {
                            double tmp = img.Height / (double)img.Width;
                            bmpOut = GenerateThumb(img, width, (int)(width * tmp));
                        }
                        if (height > 0 && width == 0)
                        {
                            double tmp = img.Width / (double)img.Height;
                            bmpOut = GenerateThumb(img, (int)(height * tmp), height);
                        }
                        if (height > 0 && width > 0)
                        {
                            bmpOut = GenerateThumb(img, width, height);
                        }
                        if (height == 0 && width == 0)
                        {
                            bmpOut = GenerateThumb(img, img.Width, img.Height);
                        }
                        if (GetContentType(extension) == "image/jpeg")
                        {
                            var info = ImageCodecInfo.GetImageEncoders();
                            var encoderParameters = new EncoderParameters(1);
                            encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, 100L);
                            if (bmpOut != null) bmpOut.Save(ms, info[1], encoderParameters);
                        }
                        else if (bmpOut != null) bmpOut.Save(ms, GetImageFormat(extension));
                        var arrImg = new byte[ms.Length];
                        ms.Position = 0;
                        ms.Read(arrImg, 0, (int)ms.Length);
                        img.Dispose();
                        context.Response.ContentType = GetContentType(extension);

                        context.Response.BinaryWrite(arrImg);
                        context.Response.End();
                    }
                }
            }

        }

        private static Bitmap GenerateThumb(Bitmap bmp, int width, int height)
        {
            Bitmap result = null;

            try
            {
                var sourceWidth = bmp.Width;
                var sourceHeight = bmp.Height;
                if (width > sourceWidth) width = sourceWidth;
                if (height > sourceHeight) height = sourceHeight;
                var widthPercent = (width / (float)sourceWidth);
                var heightPercent = (height / (float)sourceHeight);
                var finalPercent = heightPercent < widthPercent ? widthPercent : heightPercent;
                var destWidth = (int)(sourceWidth * finalPercent);
                var destHeight = (int)(sourceHeight * finalPercent);
                result = new Bitmap(width, height, PixelFormat.Format24bppRgb);
                result.SetResolution(bmp.HorizontalResolution, bmp.VerticalResolution);
                var graphics = Graphics.FromImage(result);
                graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                graphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
                graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                graphics.FillRectangle(Brushes.White, 0, 0, width, height);
                graphics.DrawImage(bmp, new Rectangle(0, 0, destWidth, destHeight),
                    new Rectangle(0, 0, sourceWidth, sourceHeight), GraphicsUnit.Pixel);
                bmp.Dispose();
                graphics.Dispose();
            }
            catch
            { }
            return result;
        }

        private static ImageFormat GetImageFormat(string ext)
        {
            switch (ext.ToLower())
            {
                case ".gif": return ImageFormat.Gif;
                case ".jpg":
                case ".jpeg": return ImageFormat.Jpeg;
                case ".png": return ImageFormat.Png;
                case ".bmp": return ImageFormat.Bmp;
                default: throw new NotSupportedException("Invalid Image Format");
            }
        }
        private static string GetContentType(string ext)
        {
            switch (ext.ToLower())
            {
                case ".gif": return "image/gif";
                case ".jpg":
                case ".jpeg": return "image/jpeg";
                case ".png": return "image/png";
                case ".bmp": return "image/bmp";
                default: throw new NotSupportedException("Invalid Image Format");
            }
        }
        public bool IsReusable
        {
            get
            {
                return true;
            }
        }
    }
}

Usage

To use this Handler, make following changes in web.config file.

Now you are all set to use this Handler. Call this handler be appending ".ashx" in the Image URL
example:
http://www.example.com/images/test.jpg.ashx?w=125&h=125
in the above URL,
w = Width of thumbnail (Optional Parameter)
h = Height of thumbnail (Optional Parameter)

Click Here to download the Sample Code. Don't forget to leave your comments.