misc WebRSize improvements

src/MagicScaler/Core/ProcessImageSettings.cs

@@ -252,7 +252,7 @@ public static ProcessImageSettings FromDictionary(IDictionary<string, string> di
 				FrameIndex = Math.Max(int.TryParse(dic.GetValueOrDefault("frame") ?? dic.GetValueOrDefault("page"), out int f) ? f : 0, 0),
 				Width = Math.Max(int.TryParse(dic.GetValueOrDefault("width") ?? dic.GetValueOrDefault("w"), out int w) ? w : 0, 0),
 				Height = Math.Max(int.TryParse(dic.GetValueOrDefault("height") ?? dic.GetValueOrDefault("h"), out int h) ? h : 0, 0),
-				JpegQuality = Math.Max(int.TryParse(dic.GetValueOrDefault("quality"), out int q) ? q : 0, 0)
+				JpegQuality = Math.Max(int.TryParse(dic.GetValueOrDefault("quality") ?? dic.GetValueOrDefault("q"), out int q) ? q : 0, 0)
 			};
 
 			s.Sharpen = bool.TryParse(dic.GetValueOrDefault("sharpen"), out bool bs) ? bs : s.Sharpen;

src/WebRSize/WebRSizeHandler.cs

@@ -3,6 +3,7 @@
 using System.Web;
 using System.Web.Hosting;
 using System.Reflection;
+using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Collections.Concurrent;
@@ -107,22 +108,29 @@ public override async Task ProcessRequestAsync(HttpContext ctx)
 
 			if (tsource?.Task == task)
 			{
-				ctx.Trace.Write("ProcessImage Begin");
+				ctx.Trace.Write(nameof(WebRSize), $"{nameof(MagicImageProcessor.ProcessImage)} Begin");
 				await process(tsource, ctx.Request.Path, cachePath, s);
-				ctx.Trace.Write("ProcessImage End");
+				ctx.Trace.Write(nameof(WebRSize), $"{nameof(MagicImageProcessor.ProcessImage)} End");
 			}
 
-			var res = await task;
+			var img = await task;
+			var res = ctx.Response;
 
-			if (!ctx.Response.IsClientConnected)
+			if (!res.IsClientConnected)
 				return;
 
-			ctx.Response.BufferOutput = false;
-			ctx.Response.ContentType = MimeMapping.GetMimeMapping(Path.GetFileName(cachePath));
-			ctx.Response.AddHeader("Content-Length", res.Count.ToString());
-			ctx.Response.Cache.SetLastModifiedFromFileDependencies();
+			try
+			{
+				res.BufferOutput = false;
+				res.ContentType = MimeMapping.GetMimeMapping(Path.GetFileName(cachePath));
+				res.AddHeader("Content-Length", img.Count.ToString());
 
-			await ctx.Response.OutputStream.WriteAsync(res.Array, res.Offset, res.Count);
+				await res.OutputStream.WriteAsync(img.Array, img.Offset, img.Count);
+			}
+			catch (HttpException ex) when (new StackTrace(ex).GetFrame(0)?.GetMethod().Name == "RaiseCommunicationError")
+			{
+				// no problem here.  client just disconnected before transmission completed.
+			}
 		}
 
 		public override bool IsReusable => true;

src/WebRSize/WebRSizeModule.cs

@@ -37,6 +37,15 @@ private async Task mapRequest(object sender, EventArgs e)
 				dic = folderConfig.DefaultSettings.ToDictionary().Coalesce(dic);
 
 			var s = ProcessImageSettings.FromDictionary(dic);
+
+			int rw = s.Width, rh = s.Height;
+			if (double.TryParse(dic.GetValueOrDefault("devicepixelratio") ?? dic.GetValueOrDefault("dpr"), out double dpr))
+			{
+				dpr = dpr.Clamp(1d, 5d);
+				s.Width = (int)Math.Floor(s.Width * dpr);
+				s.Height = (int)Math.Floor(s.Height * dpr);
+			}
+
 			if (exists && s.IsEmpty && !folderConfig.ForceProcessing)
 				return;
 
@@ -51,6 +60,7 @@ private async Task mapRequest(object sender, EventArgs e)
 					s.Width = s.Height = 100;
 
 				ifi = new ImageFileInfo(s.Width > 0 ? s.Width : s.Height, s.Height > 0 ? s.Height : s.Width);
+				s.SaveFormat = FileFormat.Png;
 			}
 
 			ifi = ifi ?? await CacheHelper.GetImageInfoAsync(path);
@@ -80,8 +90,14 @@ private async Task mapRequest(object sender, EventArgs e)
 				return;
 			}
 
-			var cacheVPath = namingStrategy.Value.GetCacheFilePath(path, s);
-			var cachePath = HostingEnvironment.MapPath(cacheVPath);
+			if (dpr > 0d && !dic.ContainsKey("quality") && !dic.ContainsKey("q"))
+			{
+				dpr = Math.Max(Math.Max((double)s.Width / (rw > 0 ? rw : s.Width), (double)s.Height / (rh > 0 ? rh : s.Height)), 1d);
+				s.JpegQuality -= (int)Math.Round((dpr - 1d) * 10);
+			}
+
+			string cacheVPath = namingStrategy.Value.GetCacheFilePath(path, s);
+			string cachePath = HostingEnvironment.MapPath(cacheVPath);
 
 			if (File.Exists(cachePath))
 			{