Preview document template pdf

Renders document template pdfs to an image which is displayed in the
configuration ui.

Disco.Services/Disco.Services.csproj

@@ -261,7 +261,7 @@
     <Compile Include="Documents\AttachmentImport\ImportDirectoryMonitor.cs" />
     <Compile Include="Documents\AttachmentImport\ImportPage.cs" />
     <Compile Include="Documents\DocumentsLog.cs" />
-    <Compile Include="Documents\DocumentTemplateActionExtensions.cs" />
+    <Compile Include="Documents\DocumentTemplateExtensions.cs" />
     <Compile Include="Documents\DocumentTemplateDataStoreExtensions.cs" />
     <Compile Include="Documents\DocumentTemplateExpressionExtensions.cs" />
     <Compile Include="Documents\DocumentUniqueIdentifier.cs" />

Disco.Services/Documents/DocumentTemplateActionExtensions.cs

@@ -1,15 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace Disco.Services
-{
-    public static class DocumentTemplateActionExtensions
-    {
-
-
-
-    }
-}

Disco.Services/Documents/DocumentTemplateExtensions.cs

@@ -0,0 +1,90 @@
+using Disco.Data.Repository;
+using Disco.Models.Repository;
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Disco.Services
+{
+    public static class DocumentTemplateActionExtensions
+    {
+
+        public static Bitmap GenerateTemplatePreview(this DocumentTemplate DocumentTemplate, DiscoDataContext Database, int Width, int PageGapHeight, bool DrawPageBorder)
+        {
+            string filename = DocumentTemplate.RepositoryFilename(Database);
+
+            if (File.Exists(filename))
+            {
+
+                using (var fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read))
+                {
+                    using (var pdfDocument = PdfiumViewer.PdfDocument.Load(fileStream))
+                    {
+                        var pageMaxWidth = (int)pdfDocument.PageSizes.Max(s => s.Width);
+                        var pageScale = (float)(Width + (DrawPageBorder ? -2 : 0)) / pageMaxWidth;
+
+                        var previewTotalHeight = pdfDocument.PageSizes
+                            .Take(40)
+                            .Select(s => (int)(pageScale * s.Height))
+                            .Sum() +
+                                (DrawPageBorder ? (Math.Min(40, pdfDocument.PageCount) * 2) : 0) +
+                                ((Math.Min(40, pdfDocument.PageCount) - 1) * PageGapHeight);
+
+                        var result = new Bitmap(Width, previewTotalHeight);
+                        result.SetResolution(72, 72);
+
+                        using (var graphics = Graphics.FromImage(result))
+                        {
+                            var yPosition = 0;
+
+                            for (int pageIndex = 0; pageIndex < Math.Min(40, pdfDocument.PageCount); pageIndex++)
+                            {
+                                var pageSize = pdfDocument.PageSizes[pageIndex];
+                                var previewWidth = Math.Floor(pageScale * pageSize.Width);
+                                var previewHeight = Math.Floor(pageScale * pageSize.Height);
+
+                                // Calculate box
+                                var destination = new Rectangle(
+                                    x: (int)((Width - previewWidth) / 2),
+                                    y: yPosition + (DrawPageBorder ? 1 : 0),
+                                    width: (int)previewWidth,
+                                    height: (int)previewHeight
+                                    );
+
+                                // Fill white background
+                                graphics.FillRectangle(Brushes.White, destination);
+
+                                using (var image = pdfDocument.Render(pageIndex, (int)previewWidth, (int)previewHeight, 72F, 72F, false))
+                                {
+                                    graphics.DrawImage(image, destination.X, destination.Y);
+                                }
+
+                                if (DrawPageBorder)
+                                {
+                                    destination.X -= 1;
+                                    destination.Y -= 1;
+                                    destination.Width += 1;
+                                    destination.Height += 1;
+                                    graphics.DrawRectangle(Pens.LightGray, destination);
+                                }
+
+                                yPosition += destination.Height + PageGapHeight;
+                            }
+                        }
+
+                        return result;
+                    }
+                }
+
+            }
+
+            return null;
+        }
+
+
+    }
+}