Respect screen DPI when obtaining thumbnails

QuickLook/Plugin/InfoPanel/DpiHelpers.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Drawing;
+using System.Runtime.InteropServices;
+
+namespace QuickLook.Plugin.InfoPanel
+{
+    internal static class DpiHelper
+    {
+        public enum DeviceCap
+        {
+            /// <summary>
+            ///     Logical pixels inch in X
+            /// </summary>
+            LOGPIXELSX = 88,
+            /// <summary>
+            ///     Logical pixels inch in Y
+            /// </summary>
+            LOGPIXELSY = 90
+        }
+
+        public const float DEFAULT_DPI = 96;
+
+        public static Dpi GetCurrentDpi()
+        {
+            var g = Graphics.FromHwnd(IntPtr.Zero);
+            var desktop = g.GetHdc();
+
+            var dpi = new Dpi
+            {
+                HorizontalDpi = GetDeviceCaps(desktop, (int) DeviceCap.LOGPIXELSX),
+                VerticalDpi = GetDeviceCaps(desktop, (int) DeviceCap.LOGPIXELSY)
+            };
+
+            return dpi;
+        }
+
+        [DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
+        public static extern int GetDeviceCaps(IntPtr hDC, int nIndex);
+    }
+
+    internal class Dpi
+    {
+        public float HorizontalDpi { get; set; }
+        public float VerticalDpi { get; set; }
+    }
+}

QuickLook/Plugin/InfoPanel/InfoPanel.xaml

@@ -10,7 +10,7 @@
             <ColumnDefinition Width="150" />
             <ColumnDefinition Width="65*" />
         </Grid.ColumnDefinitions>
-        <Image x:Name="image" Grid.Column="0" Height="128" Width="128" Stretch="None" Margin="0,-20,0,0" />
+        <Image x:Name="image" Grid.Column="0" Height="128" Width="128" Stretch="Fill" Margin="0,-20,0,0" />
         <Grid Grid.Column="1">
             <Grid.ColumnDefinitions>
                 <ColumnDefinition Width="70" />

QuickLook/Plugin/InfoPanel/InfoPanel.xaml.cs

@@ -26,7 +26,9 @@ namespace QuickLook.Plugin.InfoPanel
         public void DisplayInfo(string path)
         {
             var icon =
-                WindowsThumbnailProvider.GetThumbnail(path, 256, 256,
+                WindowsThumbnailProvider.GetThumbnail(path,
+                    (int) (128 * DpiHelper.GetCurrentDpi().HorizontalDpi / DpiHelper.DEFAULT_DPI),
+                    (int) (128 * DpiHelper.GetCurrentDpi().VerticalDpi / DpiHelper.DEFAULT_DPI),
                     ThumbnailOptions.ScaleUp);
 
             image.Source = icon.ToBitmapSource();

QuickLook/QuickLook.csproj

@@ -80,6 +80,7 @@
     <Compile Include="Controls\VisualTargetPresentationSource.cs" />
     <Compile Include="ExtensionMethods\TypeExtensions.cs" />
     <Compile Include="PluginManager.cs" />
+    <Compile Include="Plugin\InfoPanel\DpiHelpers.cs" />
     <Compile Include="Plugin\InfoPanel\Extensions.cs" />
     <Compile Include="Plugin\InfoPanel\FileHelper.cs" />
     <Compile Include="Plugin\InfoPanel\InfoPanel.xaml.cs">