PdfSharp - Tile pages rotating horizontal pages and preserving aspect ratio

TwoPagesOnOne with rotation and correct apect ratio.cs

        #region PdfSharpHelpers
        internal static bool isPdfPageHorizontal(ref XPdfForm form)
        {
            return (form.PointHeight < form.PointWidth);
        }

        static XRect scalePDFPageKeepAspectRatio(XRect maxdim, ref XPdfForm form)
        {


            XRect outDim = maxdim;
            double aspectRatioOrig = form.PointHeight / form.PointWidth;

            // Figure out the ratio
            double ratioX = maxdim.Width / form.PointWidth;
            double ratioY = maxdim.Height / form.PointHeight;
            // use whichever multiplier is smaller
            double ratio = ratioX < ratioY ? ratioX : ratioY;

            if (isPdfPageHorizontal(ref form))
            {
                outDim.Height = form.PointHeight * ratio;
                outDim.Width = form.PointWidth * ratio;
            }
            else
            {
                outDim.Height = form.PointHeight * ratio;
                outDim.Width = form.PointWidth * ratio;
            }

            return outDim;
        }




        internal static bool PdfTileOnA4Horizontal(string sInputFile, string sOutputFile, double margin = 0.0)
        {
            try
            {

                // Create the output document
                PdfDocument outputDocument = new PdfDocument();

                // Show single pages
                // (Note: one page contains two pages from the source document)
                outputDocument.PageLayout = PdfPageLayout.SinglePage;


                // Open the external document as XPdfForm object
                XPdfForm form = XPdfForm.FromFile(sInputFile);

                for (int idx = 0; idx < form.PageCount; idx += 2)
                {
                    // Add a new page to the output document
                    PdfPage page = outputDocument.AddPage();
                    page.Size = PageSize.A4;
                    page.Orientation = PageOrientation.Landscape;
                    double width = page.Width;
                    double height = page.Height;

                    int rotate = page.Elements.GetInteger("/Rotate");

                    XGraphics gfx = XGraphics.FromPdfPage(page);

                    form.PageNumber = idx + 1;




                    // TODO: center resized pages


                    XRect box = new XRect(0, 0, width / 2, height); // 0,0 i polowa szerokosci i cala wysokosc 
                    gfx.Save();
                    if (isPdfPageHorizontal(ref form))
                    {
                        gfx.RotateTransform(-90);

                        box = new XRect(0, 0, box.Height - (2 * margin), box.Width - (2 * margin));
                        box = scalePDFPageKeepAspectRatio(box, ref form);

                        gfx.TranslateTransform(-page.Height.Point + margin, 0.0 + margin);
                    }
                    else
                    {
                        box = new XRect(0, 0, box.Width - (2 * margin), box.Height - (2 * margin));
                        box = scalePDFPageKeepAspectRatio(box, ref form);

                        gfx.TranslateTransform(margin, margin);
                    }

                    gfx.DrawImage(form, box);
                    gfx.Restore();

                    if (idx + 1 < form.PageCount)
                    {
                        // Set page number (which is one-based)
                        form.PageNumber = idx + 2;

                        box = new XRect(width / 2, 0, width / 2,
                            height); // polowa szerokosci docelowej kartki, na dole kartki

                        gfx.Save();
                        if (isPdfPageHorizontal(ref form))
                        {
                            gfx.RotateTransform(-90);
                            box = new XRect(0, 0, box.Height - (2 * margin), box.Width - (2 * margin));
                            box = scalePDFPageKeepAspectRatio(box, ref form);

                            gfx.TranslateTransform(-page.Height.Point + margin, (page.Width.Point / 2.0) + margin);
                        }
                        else
                        {
                            box = new XRect(0, 0, box.Width - (2 * margin), box.Height - (2 * margin));
                            box = scalePDFPageKeepAspectRatio(box, ref form);

                            gfx.TranslateTransform((width / 2.0) + margin, margin);
                        }

                        gfx.DrawImage(form, box);
                        gfx.Restore();
                    }

                }

                // Save the document...
                outputDocument.Save(sOutputFile);

                return true;
            }
            catch (Exception exc) // FIXME: detailed catch would be better...
            {
                logger.Error(exc);
            }
            return false;
        }

        #endregion