Spire.PDF常见问题解答

为方便使用者快速掌握和了解Spire.PDF，本文列举了PDF理控件Spire.pdf常见问题及解答欢迎下载最新版体验！

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如何将 HTML 代码转换为 PDF？

A：Spire.PDF 无法加载包含 html 代码的字符串。但是 Spire.Doc 可以加载它并且 Spire.Doc 支持 PDF 格式。所以你可以使用 Spire.Doc 来完成这项工作。完整代码：

string htmlstring = "<!DOCTYPE html><html><body><h1>Header 1</h1><p>First paragraph</p></body></html>";
Document doc = new Document();
Section sec = doc.AddSection();
Paragraph para = sec.AddParagraph();

//add html code to document
para.AppendHTML(htmlstring);

//save document as PDF format
doc.SaveToFile("result.pdf", FileFormat.PDF);

如何在表格的单元格中嵌入另一个表格？

A：表格是一个更简单的网格。在网格中，您可以操作每个单元格，为每个单元格设置不同的样式并嵌入另一个网格。所以你可以使用网格来完成这项工作。完整代码：

PdfDocument document = new PdfDocument();
PdfPageBase page = document.Pages.Add(PdfPageSize.A4);

PdfGrid grid = new PdfGrid();
grid.Columns.Add(1);
grid.Columns[0].Width = page.Canvas.ClientSize.Width;
PdfGridRow row0 = grid.Rows.Add();
row0.Cells[0].Value = "This is the first row.";
row0.Cells[0].StringFormat = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);
PdfGridRow row1 = grid.Rows.Add();
PdfLayoutResult result=grid.Draw(page, new PointF(0, 20));

PdfGrid grid2 = new PdfGrid();
grid2.Columns.Add(2);
PdfGridRow newrow = grid2.Rows.Add();
grid2.Columns[0].Width = grid.Columns[0].Width / 2;
grid2.Columns[1].Width = grid.Columns[0].Width / 2;
newrow.Cells[0].Value = "This is row two column one.";
newrow.Cells[0].StringFormat = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);
newrow.Cells[1].Value = "This is row two column two.";
newrow.Cells[1].StringFormat = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);

//assign grid2 to row1
row1.Cells[0].Value = grid2;

//drwa grid2
result = grid2.Draw(page, new PointF(0, result.Bounds.Location.Y + result.Bounds.Height));
document.SaveToFile("result.pdf");

如何合并网格中的单元格？

A：Spire.PDF 为您提供名为 RowSpan 和 ColumnSpan 的属性来合并单元格。完整代码：

PdfDocument doc = new PdfDocument();
PdfPageBase page = doc.Pages.Add();

PdfGrid grid = new PdfGrid();
grid.Columns.Add(5);
float width = page.Canvas.ClientSize.Width - (grid.Columns.Count + 1);
for (int i = 0; i < grid.Columns.Count; i++)
{
grid.Columns[i].Width = width * 0.20f;
}
PdfGridRow row0 = grid.Rows.Add();
PdfGridRow row1 = grid.Rows.Add();

row0.Style.Font = new PdfTrueTypeFont(new Font("Arial", 16f, FontStyle.Bold), true);
row1.Style.Font = new PdfTrueTypeFont(new Font("Arial", 16f, FontStyle.Italic), true);

row0.Cells[0].Value = "Corporation";

//merge with the downside cell
row0.Cells[0].RowSpan = 2;

row0.Cells[1].Value = "B&K Undersea Photo";
row0.Cells[1].StringFormat = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);

//merge with the right cell
row0.Cells[1].ColumnSpan = 3;

row0.Cells[4].Value = "World";
row0.Cells[4].Style.Font = new PdfTrueTypeFont(new Font("Arial", 10f, FontStyle.Bold | FontStyle.Italic), true);
row0.Cells[4].StringFormat = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);
row0.Cells[4].Style.BackgroundBrush = PdfBrushes.LightGreen;

row1.Cells[1].Value = "Diving International Unlimited";
row1.Cells[1].StringFormat = new PdfStringFormat(PdfTextAlignment.Center, PdfVerticalAlignment.Middle);
row1.Cells[1].ColumnSpan = 4;

grid.Draw(page, new PointF(0, 0));

doc.SaveToFile("result.pdf");

如何在 PDF 文件中添加签名？

A：首先，使用类 PdfCertificate 创建一个证书实例。证书实例将用于创建 PdfSignature 实例。然后使用类 PdfSignature 创建一个签名实例。并且您需要设置签名实例的属性。完整代码：

PdfDocument doc = new PdfDocument();
doc.LoadFromFile("sample.pdf");
PdfCertificate cert = new PdfCertificate("Demo.pfx", "e-iceblue");

//add signature to every page of PDF file
foreach (PdfPageBase page in doc.Pages)
{
PdfSignature signature = new PdfSignature(page.Document, page, cert, "demo");
signature.ContactInfo = "Harry";
signature.Certificated = true;
signature.DocumentPermissions = PdfCertificationFlags.AllowFormFill;
}

doc.SaveToFile("result.pdf");

如何重新排列 PDF 文件的页面？

A : 请调用 ReArrange 方法。该方法将一个 int 数组作为参数。int 数组表示页面的新顺序。完整代码：

PdfDocument document = new PdfDocument();

//sample.pdf has four pages
document.LoadFromFile("sample.pdf");

//rearrange the pages of the PDF file
int[] range = new int[] { 0, 2, 1, 3 };
document.Pages.ReArrange(range);
document.SaveToFile("result.pdf");

如何添加图片水印？

A : Spire.PDF 不直接支持图片水印。但是您可以将图像设置为 BackgroundImage。如果图像足够大，BackgroundImage 就像图像水印一样。完整代码：

PdfDocument document = new PdfDocument();
PdfPageBase page = document.Pages.Add(PdfPageSize.A4);
page.Canvas.DrawString("This is a demo about image watermark!",
new PdfFont(PdfFontFamily.Helvetica, 25f),
new PdfSolidBrush(Color.Green),
10, 40);

//set image as BackgroundImage to make image watermark
Image img = Image.FromFile("scene.bmp");
page.BackgroundImage = img;
document.SaveToFile("result.pdf");

如何在所有页面上重复标题？

A : PdfDocumentTemplate 中的内容将适用于 PDF 文件的每一页。您所要做的就是创建一个将标题添加到 PdfDocumentTemplate 的方法。然后标题将添加到每个页面。完整代码：

static void Main(string[] args)
{
PdfDocument doc = new PdfDocument();
PdfUnitConvertor unitCvtr = new PdfUnitConvertor();
PdfMargins margin = new PdfMargins();
margin.Top = unitCvtr.ConvertUnits(3.0f, PdfGraphicsUnit.Centimeter, PdfGraphicsUnit.Point);
margin.Bottom = margin.Top;
margin.Left = unitCvtr.ConvertUnits(3.17f, PdfGraphicsUnit.Centimeter, PdfGraphicsUnit.Point);
margin.Right = margin.Left;


// create three page
PdfPageBase page = doc.Pages.Add(PdfPageSize.A4, margin);
page = doc.Pages.Add(PdfPageSize.A4, margin);
page = doc.Pages.Add(PdfPageSize.A4, margin);

//apply template
SetDocumentTemplate(doc, PdfPageSize.A4, margin);
doc.SaveToFile("result.pdf");

}
//method to add header to every page
private static void SetDocumentTemplate(PdfDocument doc, SizeF pageSize, PdfMargins margin)
{
PdfPageTemplateElement leftSpace
= new PdfPageTemplateElement(margin.Left, pageSize.Height);
doc.Template.Left = leftSpace;

PdfPageTemplateElement topSpace
= new PdfPageTemplateElement(pageSize.Width, margin.Top);
topSpace.Foreground = true;
doc.Template.Top = topSpace;

//draw header label
PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Arial", 9f, FontStyle.Italic));
PdfStringFormat format = new PdfStringFormat(PdfTextAlignment.Right);
String label = "Demo about Header Repeating";

//set the header style
SizeF size = font.MeasureString(label, format);
float y = topSpace.Height - font.Height - 40;
PdfPen pen = new PdfPen(Color.Black, 0.75f);
topSpace.Graphics.SetTransparency(0.5f);
topSpace.Graphics.DrawLine(pen, margin.Left - 30, y, pageSize.Width - margin.Right + 30, y);
y = y - 1 - size.Height;
topSpace.Graphics.DrawString(label, font, PdfBrushes.Black, pageSize.Width - margin.Right, y, format);

PdfPageTemplateElement rightSpace
= new PdfPageTemplateElement(margin.Right, pageSize.Height);
doc.Template.Right = rightSpace;

PdfPageTemplateElement bottomSpace
= new PdfPageTemplateElement(pageSize.Width, margin.Bottom);
bottomSpace.Foreground = true;
doc.Template.Bottom = bottomSpace;
}

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