Write initial directory preview generator implementation

GalleryShare/Extensions.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Drawing;
+
+namespace GalleryShare
+{
+	public static class Extensions
+	{
+		public static PointF Multiply(this PointF a, PointF b)
+		{
+			return new PointF(
+				a.X * b.X,
+				a.Y * b.Y
+			);
+		}
+
+		public static Point ToIntPoint(this PointF source)
+		{
+			return new Point((int)source.X, (int)source.Y);
+		}
+	}
+}
+

GalleryShare/GalleryShare.csproj

@@ -51,6 +51,7 @@
     <Compile Include="RequestRouter\RouteSpecialFile.cs" />
     <Compile Include="RequestRouter\RouteDirectoryListing.cs" />
     <Compile Include="RequestRouter\RouteDefault.cs" />
+    <Compile Include="Extensions.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup />

GalleryShare/ThumbnailGenerator.cs

@@ -5,9 +5,8 @@ using System.IO;
 
 using System.Drawing.Drawing2D;
 using System.Drawing.Imaging;
-using System.Runtime.InteropServices;
 using System.Net;
-using System.Reflection;
+using System.Collections.Generic;
 
 namespace GalleryShare
 {
@@ -26,6 +25,30 @@ namespace GalleryShare
 			imageToSend.Dispose();
 		}
 
+		public static Image GenerateDirectoryThumbnail(string dirPath, Size thumbnailSize)
+		{
+			List<string> dirFiles = new List<string>(Directory.GetFiles(dirPath));
+			dirFiles.Sort( (a, b) => File.GetLastWriteTime(a).CompareTo(File.GetLastWriteTime(b)) );
+
+			Bitmap resultImage = new Bitmap(thumbnailSize.Width, thumbnailSize.Height);
+			using(Graphics context = Graphics.FromImage(resultImage))
+			{
+				for(int i = 0; i < 4; i++)
+				{
+					using (Image fileThumbnail = GenerateFileThumbnail(
+						dirFiles[i],
+						new Size(thumbnailSize.Width, thumbnailSize.Height)
+					))
+					{
+						PointF drawingPos = getDirectoryImageDrawPosition(i).Multiply(new PointF(resultImage.Width, resultImage.Height));
+						context.DrawImage(fileThumbnail, drawingPos.ToIntPoint());
+					}
+				}
+			}
+
+			return resultImage;
+		}
+
 		public static Image GenerateFileThumbnail(string imagePath, Size thumbnailBounds)
 		{
 			try {
@@ -103,6 +126,18 @@ namespace GalleryShare
 				return mStream.ToArray();
 			}
 		}
+
+		private static PointF getDirectoryImageDrawPosition(int id)
+		{
+			switch(id)
+			{
+				case 0: return new PointF(0, 0);
+				case 1: return new PointF(0.5f, 0);
+				case 2: return new PointF(0.5f, 0.5f);
+				case 3: return new PointF(0, 0.5f);
+				default: throw new InvalidDataException($"Invalid id #{id}.");
+			}
+		}
 	}
 }