add logo to pdf - basic feature

src/PrivatePdfConverter/Commands/AddLogoToPdf.cs

@@ -1,9 +1,62 @@
+using iText.IO.Image;
+using iText.Kernel.Pdf;
+using iText.Kernel.Pdf.Canvas;
+using iText.Layout;
+using iText.Layout.Element;
+using PrivatePdfConverter.Services;
+using Serilog;
+
 namespace PrivatePdfConverter.Commands;
 
 public static class AddLogoToPdf
 {
     public static void Run(string path, string logoPath, string position, string? output)
     {
+        if (!File.Exists(path))
+        {
+            Log.Logger.Error("PDF file '{Path}' does not exist", path);
+            return;
+        }
+
+        if (!File.Exists(logoPath))
+        {
+            Log.Logger.Error("Logo image file '{LogoPath}' does not exist", logoPath);
+            return;
+        }
+
+        var outputFileName = output.PrepareOutputFileName();
+        var exportFullPath = Path.GetDirectoryName(path).AddFileToPath(outputFileName);
+        Log.Logger.Information("Read a pdf from {Path}", path);
+        using var pdfDoc = new PdfDocument(new PdfReader(path), new PdfWriter(exportFullPath));
+
+        var logo = new Image(ImageDataFactory.Create(logoPath));
+        Log.Logger.Information("Read logo {Path}, image dimensions: {Width} x {Height}", logoPath, logo.GetImageWidth(), logo.GetImageHeight());
+
+        AddLogoToPages(pdfDoc, logo);
+
+        pdfDoc.Close();
+        Log.Logger.Information("Created a new pdf at {ExportFullPath}", exportFullPath);
+    }
+
+    private static void AddLogoToPages(PdfDocument pdfDoc, Image logo)
+    {
+        var numberOfPages = pdfDoc.GetNumberOfPages();
+        for (var pageNum = 1; pageNum <= numberOfPages; pageNum++)
+        {
+            Log.Logger.Information("Adding to page {PageNumber} of {NumberOfPages}", pageNum, numberOfPages);
+            logo.SetFixedPosition(pageNum, 0, 0);
+            logo.SetAutoScaleWidth(true);
+            logo.SetAutoScaleHeight(true);
+
+            var pdfPage = pdfDoc.GetPage(pageNum);
+            var pdfCanvas = new PdfCanvas(
+                pdfPage.NewContentStreamBefore(),
+                pdfPage.GetResources(),
+                pdfDoc);
 
+            using var canvas = new Canvas(pdfCanvas, pdfPage.GetPageSize());
+            canvas.Add(logo)
+                .Close();
+        }
     }
 }