将 PDF 页面从纵向更改为横向

Question

给定一个包含纵向页面的现有 PDF 文件，我该如何以编程方式（使用 .NET）处理该文件，以便在横向页面上生成具有相同内容的新文件。

新页面应该充分利用可用的横向宽度。页面数量可能会增加，因为现有的纵向页面可能不适合一个横向页面。

背景故事:我们使用Google Sheets REST API来生成pdf文档。如果有很多列，文档可能会很宽。不幸的是，Google Drive REST API总是以纵向模式导出，并且不提供更改为横向模式的选项。

下面是我们需要处理的一个示例PDF文件:https://drive . Google . com/file/d/1 dvf 1 GD 7 zmdx 9 wjhsegebfpcvytjbn-uG/view？usp =共享

Answer 1

使用iTextSharp（iText for. Net v5.5.13）和PdfVeryDenseMergeTool和PageVerticalAnalyzer类从这个问题（在"UPDATE 2"和"UPDATE 3"中，OP从接受的C#答案发布了他的Java解决方案的端口）如下所示：

List<PdfReader> Files = new List<PdfReader>();
Files.Add(new PdfReader(@"Example.pdf"));

PdfVeryDenseMergeTool tool = new PdfVeryDenseMergeTool(new RectangleReadOnly(595, 420), 18, 18, 10);

using (MemoryStream ms = new MemoryStream())
{
    tool.Merge(ms, Files);
    byte[] bytes = ms.ToArray();
    // bytes contains the result
} 

我得到一个五页的横向结果PDF，看起来像这样：

Answer 2

您可以使用文档目录.pdf库来执行此操作。最简单的解决方案是将每个源页面转换为 XObject，然后将其缩放为横向并在多个目标页面上绘制。

以下是示例：

using System.Linq;
using BitMiracle.Docotic.Pdf;

namespace SplitToMultiplePages
{
    public static class SplitToMultiplePages
    {
        public static void Main()
        {
            // NOTE: 
            // When used in trial mode, the library imposes some restrictions.
            // Please visit http://bitmiracle.com/pdf-library/trial-restrictions.aspx
            // for more information.
            BitMiracle.Docotic.LicenseManager.AddLicenseData("temporary or permanent license key here");

            using (var src = new PdfDocument(@"Example.pdf"))
            {
                // Calculate common parameters based on the first page.
                // That makes sense when all pages have the same size, portrait orientation, and margins.
                PdfPage srcPage = src.Pages[0];
                PdfCollection<PdfTextData> words = srcPage.GetWords();

                double topMargin = words[0].Position.Y;
                double bottomMargin = srcPage.Height - words[words.Count - 1].Bounds.Bottom;
                double scale = srcPage.Height / srcPage.Width;
                const int BorderHeight = 1;

                // This sample shows how to convert existing PDF content in portrait orientation to landscape
                Debug.Assert(scale > 1);

                using (var dest = new PdfDocument())
                {
                    bool addDestPage = false;
                    double destPageY = topMargin;
                    for (int s = 0; s < src.PageCount; ++s)
                    {
                        if (s > 0)
                        {
                            srcPage = src.Pages[s];
                            words = srcPage.GetWords();
                        }

                        // skip empty pages
                        if (words.Count == 0)
                            continue;

                        // Get content of the source page, scale to landscape and draw on multiple pages
                        double textStartY = words[0].Bounds.Top;
                        double[] lineBottomPositions = words
                            .Select(w => (w.Bounds.Bottom - textStartY + BorderHeight) * scale)
                            .Distinct()
                            .ToArray();
                        double contentHeight = lineBottomPositions[lineBottomPositions.Length - 1];

                        PdfXObject xobj = dest.CreateXObject(srcPage);

                        double remainingHeight = contentHeight;
                        while (true)
                        {
                            PdfPage destPage = addDestPage ? dest.AddPage() : dest.Pages[dest.PageCount - 1];
                            destPage.Width = srcPage.Height;
                            destPage.Height = srcPage.Width;
                            double availableHeight = destPage.Height - destPageY - bottomMargin;
                            if (remainingHeight > availableHeight)
                                availableHeight = adjustToNearestLine(availableHeight, lineBottomPositions);

                            PdfCanvas destCanvas = destPage.Canvas;
                            destCanvas.SaveState();

                            destCanvas.TranslateTransform(0, destPageY);
                            destCanvas.AppendRectangle(new PdfRectangle(0, 0, destPage.Width, availableHeight), 0);
                            destCanvas.SetClip(PdfFillMode.Winding);

                            double y = -topMargin * scale - (contentHeight - remainingHeight);
                            destCanvas.DrawXObject(xobj, 0, y, xobj.Width * scale, xobj.Height * scale, 0);

                            destCanvas.RestoreState();

                            if (remainingHeight <= availableHeight)
                            {
                                // Move to next source page
                                addDestPage = false;
                                destPageY = remainingHeight + bottomMargin;
                                break;
                            }

                            // Need more pages in the resulting document
                            remainingHeight -= availableHeight;
                            addDestPage = true;
                            destPageY = topMargin;
                        }
                    }

                    // Optionally you can use Single Column layout by default
                    //dest.PageLayout = PdfPageLayout.OneColumn;

                    dest.Save("SplitToMultiplePages.pdf");
                }
            }
        }

        private static double adjustToNearestLine(double height, double[] lineHeights)
        {
            // TODO: Use binary search for better performance

            for (int i = lineHeights.Length - 1; i >= 0; --i)
            {
                double lh = lineHeights[i];
                if (height > lh)
                    return lh;
            }

            return lineHeights[0];
        }
    }
}

该样本产生以下结果：https://drive.google.com/file/d/1ITtV3Uw84wKd9mouV4kBpPoeWtsHlB9A/view?usp=sharing

根据您的要求，您也可以跳过除第一页以外的所有页面的标题。以下是这种情况的示例:

using System.Linq;
using BitMiracle.Docotic.Pdf;

namespace SplitToMultiplePages
{
    public static class SplitToMultiplePages
    {
        public static void Main()
        {
            // NOTE: 
            // When used in trial mode, the library imposes some restrictions.
            // Please visit http://bitmiracle.com/pdf-library/trial-restrictions.aspx
            // for more information.
            BitMiracle.Docotic.LicenseManager.AddLicenseData("temporary or permanent license key here");

            using (var src = new PdfDocument(@"Example.pdf"))
            {
                // Calculate common parameters based on the first page.
                // That makes sense when all pages have the same size, portrait orientation, and margins.
                PdfPage srcPage = src.Pages[0];
                PdfCollection<PdfTextData> words = srcPage.GetWords();

                double topMargin = words[0].Position.Y;
                double bottomMargin = srcPage.Height - words[words.Count - 1].Bounds.Bottom;
                double scale = srcPage.Height / srcPage.Width;
                const int BorderHeight = 1;

                // This sample shows how to convert existing PDF content in portrait orientation to landscape
                Debug.Assert(scale > 1);

                using (var dest = new PdfDocument())
                {
                    bool addDestPage = false;
                    double destPageY = topMargin;
                    for (int s = 0; s < src.PageCount; ++s)
                    {
                        if (s > 0)
                        {
                            srcPage = src.Pages[s];
                            words = srcPage.GetWords();
                        }

                        // skip empty pages
                        if (words.Count == 0)
                            continue;

                        // Get content of the source page, scale to landscape and draw on multiple pages
                        double textStartY = words[0].Bounds.Top;
                        
                        // Skip the header line of all pages except first
                        if (s > 0)
                        {
                            double? firstDataRowY = words.Select(w => w.Bounds.Top).FirstOrDefault(y => y > textStartY);
                            if (!firstDataRowY.HasValue)
                                continue;

                            textStartY = firstDataRowY.Value;
                        }

                        double[] lineBottomPositions = words
                            .Select(w => (w.Bounds.Bottom - textStartY + BorderHeight) * scale)
                            .Distinct()
                            .ToArray();
                        double contentHeight = lineBottomPositions[lineBottomPositions.Length - 1];

                        PdfXObject xobj = dest.CreateXObject(srcPage);

                        double remainingHeight = contentHeight;
                        while (true)
                        {
                            PdfPage destPage = addDestPage ? dest.AddPage() : dest.Pages[dest.PageCount - 1];
                            destPage.Width = srcPage.Height;
                            destPage.Height = srcPage.Width;
                            double availableHeight = destPage.Height - destPageY - bottomMargin;
                            if (remainingHeight > availableHeight)
                                availableHeight = adjustToNearestLine(availableHeight, lineBottomPositions);

                            PdfCanvas destCanvas = destPage.Canvas;
                            destCanvas.SaveState();

                            destCanvas.TranslateTransform(0, destPageY);
                            destCanvas.AppendRectangle(new PdfRectangle(0, 0, destPage.Width, availableHeight), 0);
                            destCanvas.SetClip(PdfFillMode.Winding);

                            double y = -textStartY * scale - (contentHeight - remainingHeight);
                            destCanvas.DrawXObject(xobj, 0, y, xobj.Width * scale, xobj.Height * scale, 0);

                            destCanvas.RestoreState();

                            if (remainingHeight <= availableHeight)
                            {
                                // Move to the next source page
                                addDestPage = false;
                                destPageY = remainingHeight + bottomMargin;
                                break;
                            }

                            // Need more pages in the resulting document
                            remainingHeight -= availableHeight;
                            addDestPage = true;
                            destPageY = topMargin;
                        }
                    }

                    // Optionally you can use Single Column layout by default
                    //dest.PageLayout = PdfPageLayout.OneColumn;

                    dest.Save("SplitToMultiplePages.pdf");
                }
            }
        }

        private static double adjustToNearestLine(double height, double[] lineHeights)
        {
            // TODO: Use binary search for better performance

            for (int i = lineHeights.Length - 1; i >= 0; --i)
            {
                double lh = lineHeights[i];
                if (height > lh)
                    return lh;
            }

            return lineHeights[0];
        }
    }
}

“skip headers”示例的结果文件:https://drive . Google . com/file/d/1v 9 lpyiposknngheuzz 8 KD 3 xswmxgbjiz/view？usp =共享