Resizeovaci image HttpHandler

Kód je downgrade produkčnej verzie resp. staršia záplatová verzia. Chýba riešenie caching-u, či už z hľadiska HTTP protokolu, ako i z hľadiska nutnosti znovagenerovať thumbnails - čo je neefektívne v prípade, že niektoré images sú častejšie zobrazované. Pracuje len s jpg, infrastruktúra ale umožnuje ľahko pridať možnosť špecifikovať formát alebo upraviť handler na iný formát. Z hľadiska zraniteľnosti aplikácie neodporúčam všeobecný interface handlera (url parametre) umožnujúci zadať ľubovolné parametre a v kontexte portieb konkrétneho druhu thumbnail validovať rozumné zosahy parametrov.

Použitie:

 <img src="img.ashx?300;300;foo;70"/>

kde src -> pattern.ashx?width;height;nazov[;quality]

using System;
using System.Drawing;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Web;
using AspNetSK.Web.UI;
using AspNetSK.Drawing;
namespace AspNetSK.Web
{
	public abstract class ImageResizeHttpHandlerBase : IHttpHandler
	{
		protected abstract string RootPath { get; }
		#region IHttpHandler Members
		public bool IsReusable
		{
			get { return true; }
		}
		public void ProcessRequest(HttpContext context)
		{
			HttpRequest request = context.Request;
			HttpResponse response = context.Response;
			string imgParams = request.Url.Query;			
			if(string.IsNullOrEmpty(imgParams))
			{
				HandleError("Invalid parameters");
				response.End();
			}
			imgParams = imgParams.Replace("?", "");
			string[] arrImgParams = imgParams.Split(new char[]{';'});
			if (arrImgParams.Length < 3)
			{
				HandleError("Invalid parameters");
				response.End();
			}
			int width, height;
			short quality = 70;			
			if(!int.TryParse(arrImgParams[0], out width) || width < 1 || width > 1200)			
			{
				HandleError("Invalid width.");
				return;
			}
			if (!int.TryParse(arrImgParams[1], out height) || height < 1 || height > 1200)
			{
				HandleError("Invalid height.");
				return;
			}
			
			string path = context.Server.MapPath(RootPath + "/" + arrImgParams[2] + ".jpg");
			if (!File.Exists(path))
			{
				WriteStatusAndTerminate(404);
				return;
			}
			
			if (arrImgParams.Length > 3)
			{
				if (!short.TryParse(arrImgParams[3], out quality) || quality < 1 || quality > 100)
				{
					HandleError("Invalid quality.");
					return;
				}
			}			
			Bitmap image = null, tmbImage = null;
			using (FileStream fileStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
				image = (Bitmap)Bitmap.FromStream(fileStream);
			try
			{
				tmbImage = ImageHelper.GetThumbNail(
					image,
					new Size(width, height),
					ScaleType.Clipp);
				
				ImageHelper.SaveCompressedJpg(
					tmbImage,
					response.OutputStream,
					quality);
			
			}
			catch(Exception ex)
			{
				HandleError(ex);
			}
			finally
			{
				if(image != null)
					image.Dispose();
				if(tmbImage != null)
					image.Dispose();
			}
		}
		protected virtual void HandleError(Exception ex)
		{
			#if DEBUG
				throw ex;
			#else
				HandleError("Error processing image", 500);
			#endif
		}
		protected virtual void HandleError(string message)
		{
			HandleError(message, 500);
		}
		protected virtual void HandleError(string message, int status)
		{
#if DEBUG
			throw new Exception(message);
#else
			WriteStatusAndTerminate(status, message);
#endif
		}
		protected virtual void WriteStatusAndTerminate(int status)
		{
			WriteStatusAndTerminate(status, null);
		}
		protected virtual void WriteStatusAndTerminate(int status, string message)
		{
			HttpResponse response= HttpContext.Current.Response;
			response.ClearHeaders();
			response.ClearContent();
			response.StatusCode = status;
			if(message != null)
				response.StatusDescription = message;
			response.End();
		}
		#endregion
	}
}

Treba urobit override pre kazdy typ handleru:

namespace AspNetSK.Web
{
	public class ArticleListTmbHttpHandler : ImageResizeHttpHandlerBase
	{
		protected override string RootPath
		{
			get { return "~/img/art/"; }
		}
	}
}

 Web.config:

<add path="img.ashx" verb="GET,HEAD" validate="false" type="AspNetSK.Web.ImageHttpHandler" /> 

A resize helper:

using System;
using System.IO;
using System.Data;
using System.Configuration;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

namespace AspNetSK.Drawing
{
	public enum ScaleType
	{
		Clipp,
		ScaleToFit,
		ScaleIntoBounds
	}

	public class ImageHelper
	{
		public static Bitmap GetThumbNail(Bitmap image, Size tmbSize, ScaleType scaleType)
		{
			int iSourceWidth = image.Width;
			int iSourceHeight = image.Height;
			if (scaleType == ScaleType.Clipp || scaleType == ScaleType.ScaleIntoBounds)
			{
				SizeF tmbSizeF = (SizeF)tmbSize;
				SizeF origSizeF = (SizeF)image.Size;
				float widthRatio = origSizeF.Width / tmbSizeF.Width;
				float heightRatio = origSizeF.Height / tmbSizeF.Height;

				if (scaleType == ScaleType.Clipp)
				{
					if (widthRatio < heightRatio)
						iSourceHeight = (int)Math.Round((double)(tmbSizeF.Height * widthRatio));
					else
						iSourceWidth = (int)Math.Round((double)(tmbSizeF.Width * heightRatio));
				}
				else
				{
					if (widthRatio > heightRatio)
						tmbSize.Height = (int)Math.Round((double)(origSizeF.Height / widthRatio));
					else
						tmbSize.Width = (int)Math.Round((double)(origSizeF.Width / heightRatio));
				}
			}

			Bitmap thumbnail = new Bitmap(tmbSize.Width, tmbSize.Height, PixelFormat.Format24bppRgb);

			using (Graphics graphics = Graphics.FromImage(thumbnail))
			{
				graphics.CompositingQuality = CompositingQuality.HighQuality;
				graphics.SmoothingMode = SmoothingMode.HighQuality;
				graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
				Rectangle oDestRectangle = new Rectangle(0, 0, tmbSize.Width, tmbSize.Height);
				Rectangle oSrcRectangle = new Rectangle(0, 0, iSourceWidth, iSourceHeight);
				graphics.DrawImage(image, oDestRectangle, oSrcRectangle, GraphicsUnit.Pixel);
			}
			return thumbnail;
		}


		public static void SaveCompressedJpg(Image img, string fileName, short compressLevel)
		{
			using (EncoderParameters codecParams = new EncoderParameters(1))			
			using (EncoderParameter param = new EncoderParameter(Encoder.Quality, (long)compressLevel))
			{
				codecParams.Param[0] = param;
				ImageCodecInfo codecInfo = FindEncoder(ImageFormat.Jpeg);
				img.Save(fileName, codecInfo, codecParams);
			}
		}

		public static void SaveCompressedJpg(Image img, Stream stream, short compressLevel)
		{
			using (EncoderParameters codecParams = new EncoderParameters(1))
			using (EncoderParameter param = new EncoderParameter(Encoder.Quality, (long)compressLevel))
			{
				codecParams.Param[0] = param;
				ImageCodecInfo codecInfo = FindEncoder(ImageFormat.Jpeg);
				img.Save(stream, codecInfo, codecParams);
			}
		}


		private static ImageCodecInfo FindEncoder(ImageFormat eImgFormat)
		{
			ImageCodecInfo[] arrCodecInfo = ImageCodecInfo.GetImageEncoders();
			ImageCodecInfo[] arrCodecInfo2 = arrCodecInfo;
			for (int i = 0; i < arrCodecInfo2.Length; i++)
			{
				ImageCodecInfo oCodecInfo = arrCodecInfo2[i];
				if (oCodecInfo.FormatID.Equals(eImgFormat.Guid))
					return oCodecInfo;
			}
			return null;
		}
	}
}