打印大型WPF画布

Question

我正在尝试使用here描述的策略打印大型WPF画布。

使用Letter或A4纸张尺寸时，一切正常。但是，当我选择以A2纸张尺寸打印时，我注意到部分图像被剪掉了。任何想法为什么会发生这种情况？

以下是打印的重要部分（至少我认为是）的代码：

private void CreateDocument()
{
    DesignerCanvas designerCanvas = _board.DesignerCanvas;

    using (new WaitCursor())
    {
        var paperSize = PaperSizeComboBox.SelectionBoxItem as PageSize;
        if (paperSize == null)
        {
            throw new Exception("Paper Size cannot be null");
        }

        bool portrait = OrientationComboBox.SelectedIndex == 0;
        double zoom = ZoomSlider.Value / 100;

        _printDialog.PrintTicket = _printDialog.PrintQueue.DefaultPrintTicket;
        _printDialog.PrintTicket.PageMediaSize = paperSize.PageMediaSize;
        _printDialog.PrintTicket.PageOrientation = (portrait)
            ? PageOrientation.Portrait
            : PageOrientation.Landscape;
        _printDialog.PrintQueue.GetPrintCapabilities();

        var fixedDocument = new FixedDocument();

        var designerCanvasSize = new Size(designerCanvas.ActualWidth * zoom,
            designerCanvas.ActualHeight * zoom);
        var boardSize = new Size(_board.ExtentWidth, _board.ExtentHeight);

        double xOffset = _board.HorizontalOffset;
        double yOffset = _board.VerticalOffset;

        double pageWidth = _printDialog.PrintableAreaWidth;
        double pageHeight = _printDialog.PrintableAreaHeight;

        double coveredX = 0;
        double coveredY = 0;

        double totalX = designerCanvasSize.Width;
        double totalY = designerCanvasSize.Height;

        int pageNumber = 1;

        while (true)
        {
            double x = pageWidth;
            double y = pageHeight;

            if ((coveredX + pageWidth) > totalX)
            {
                x = totalX - coveredX;
            }
            if ((coveredY + pageHeight) > totalY)
            {
                y = totalY - coveredY;
            }

            double dpiX = 300.0;
            double dpiY = 300.0;
            double dpiScale = 300.0 / 96.0;

            var crop = new Rect(xOffset * -1, yOffset * -1, x * dpiX, y * dpiY);
            _board.Measure(boardSize);
            _board.Arrange(crop);

            int imgWidth = Convert.ToInt32(x * dpiScale);
            int imgHeight = Convert.ToInt32(y * dpiScale);

            var renderBitmap = new RenderTargetBitmap(imgWidth, imgHeight, dpiX, dpiY, PixelFormats.Pbgra32);
            renderBitmap.Render(_board);
            renderBitmap.Freeze();

            using (var outStream = new MemoryStream())
            {
                var encoder = new PngBitmapEncoder();
                encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
                encoder.Save(outStream);
                outStream.Seek(0, SeekOrigin.Begin);

                var bitmapImage = new BitmapImage();
                bitmapImage.BeginInit();
                bitmapImage.CacheOption = BitmapCacheOption.OnLoad;
                bitmapImage.StreamSource = outStream;
                bitmapImage.EndInit();
                var image = new Image { Source = bitmapImage };

                var pageGrid = new Grid { Margin = new Thickness(0), Width = pageWidth, Height = pageHeight };

                image.HorizontalAlignment = HorizontalAlignment.Left;
                image.VerticalAlignment = VerticalAlignment.Top;

                RenderOptions.SetBitmapScalingMode(image, BitmapScalingMode.NearestNeighbor);
                RenderOptions.SetEdgeMode(image, EdgeMode.Aliased);

                var border = new Border
                {
                    BorderThickness = new Thickness(1),
                    BorderBrush = Brushes.Transparent,
                    Margin = new Thickness(28),
                    Padding = new Thickness(2),
                    Child = image
                };

                pageGrid.Children.Add(border);

                if (ShowPageNumberCheckBox.IsChecked != null && ShowPageNumberCheckBox.IsChecked == true)
                {
                    var lblPageNumber = new Label
                    {
                        Content = string.Format("{0}", pageNumber++),
                        HorizontalAlignment = HorizontalAlignment.Right,
                        VerticalAlignment = VerticalAlignment.Top,
                        Margin = new Thickness(20),
                        Foreground = Brushes.Black,
                    };
                    pageGrid.Children.Add(lblPageNumber);
                }

                var pageContent = new PageContent();
                var page = new FixedPage { Width = pageWidth, Height = pageHeight };
                page.Children.Add(pageGrid);

                ((IAddChild)pageContent).AddChild(page);
                fixedDocument.Pages.Add(pageContent);
            }

            xOffset += x;
            coveredX += x;

            if (coveredX >= totalX)
            {
                xOffset = _board.HorizontalOffset;
                coveredX = 0;
                yOffset += y;
                coveredY += y;
                if (coveredY >= totalY)
                {
                    break;
                }
            }
            Dispose();
        }

        _printDialog.PrintDocument(fixedDocument.DocumentPaginator, string.Format("bord_{0}", _board.Nome));
    }
}

这是两种纸张尺寸的结果页：