Fix #154: Switch to Pdfium; better PDF async loading

QuickLook.Plugin/QuickLook.Plugin.PDFViewer/PdfPageExtension.cs

@@ -0,0 +1,54 @@
+// Copyright © 2017 Paddy Xu
+// 
+// This file is part of QuickLook program.
+// 
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+using System;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using PDFiumSharp;
+using QuickLook.Helpers;
+
+namespace QuickLook.Plugin.PDFViewer
+{
+    internal static class PdfPageExtension
+    {
+        public static BitmapSource RenderThumbnail(this PdfPage page)
+        {
+            var factorX = 130d / page.Width;
+            var factorY = 210d / page.Height;
+
+            return page.Render(Math.Min(factorX, factorY), false);
+        }
+
+        public static BitmapSource Render(this PdfPage page, double factor, bool fixDpi = true)
+        {
+            var scale = DpiHelper.GetCurrentScaleFactor();
+            var dpiX = fixDpi ? scale.Horizontal * DpiHelper.DefaultDpi : 96;
+            var dpiY = fixDpi ? scale.Vertical * DpiHelper.DefaultDpi : 96;
+
+            var realWidth = (int) Math.Ceiling(page.Width * (dpiX / 72) * factor);
+            var realHeight = (int) Math.Ceiling(page.Height * (dpiY / 72) * factor);
+
+            var bitmap = new WriteableBitmap(realWidth, realHeight, dpiX, dpiY, PixelFormats.Bgr24, null);
+            page.Render(bitmap,
+                flags: RenderingFlags.LimitImageCache | RenderingFlags.Annotations | RenderingFlags.DontCatch |
+                       RenderingFlags.LcdText);
+
+            bitmap.Freeze();
+            return bitmap;
+        }
+    }
+}