iTextSharp-PDF-调整文档大小以适应大图像

iText和iTextSharp中的Document对象是一个抽象，可以自动处理各种间距、填充和边距。不幸的是，这也意味着当您调用doc.Add()时，它会考虑文档的现有边距。（此外，如果你碰巧添加了其他任何东西，图像也会被添加。）

一个解决方案是只去除利润：

doc.SetMargins(0, 0, 0, 0);

相反，可以更容易地将图像直接添加到PdfWriter对象中，这是通过调用PdfWriter.GetInstance()获得的。你目前正在扔掉并没有存储该对象，但你可以很容易地将你的行更改为：

PdfWriter writer = PdfWriter.GetInstance(doc, new FileStream(saveFileDialog1.FileName,FileMode.Create));

然后您可以访问PdfWriter的DirectContent属性，并调用其AddImage()方法：

writer.DirectContent.AddImage(img);

在进行此操作之前，您还必须通过调用来绝对定位图像

img.SetAbsolutePosition(0, 0);

下面是一个完整的C#2010 WinForms应用程序，目标是iTextSharp 5.1.1.0，它显示了上面的DirectContent方法。它动态地创建了两个不同大小的图像，两个红色箭头垂直和水平延伸。您的代码显然只使用标准的图像加载，因此可以省略很多内容，但我想提供一个完整的工作示例。有关更多详细信息，请参阅代码中的注释。

using System;
using System.Drawing;
using System.Windows.Forms;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
namespace WindowsFormsApplication1 {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e) {
            //File to write out
            string outputFilename = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Images.pdf");
            //Standard PDF creation
            using (FileStream fs = new FileStream(outputFilename, FileMode.Create, FileAccess.Write, FileShare.None)) {
                //NOTE, we are not setting a document size here at all, we'll do that later
                using (Document doc = new Document()) {
                    using (PdfWriter writer = PdfWriter.GetInstance(doc, fs)) {
                        doc.Open();
                        //Create a simple bitmap with two red arrows stretching across it
                        using (Bitmap b1 = new Bitmap(100, 400)) {
                            using (Graphics g1 = Graphics.FromImage(b1)) {
                                using(Pen p1 = new Pen(Color.Red,10)){
                                    p1.StartCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;
                                    p1.EndCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;
                                    g1.DrawLine(p1, 0, b1.Height / 2, b1.Width, b1.Height / 2);
                                    g1.DrawLine(p1, b1.Width / 2, 0, b1.Width / 2, b1.Height);
                                    //Create an iTextSharp image from the bitmap (we need to specify a background color, I think it has to do with transparency)
                                    iTextSharp.text.Image img1 = iTextSharp.text.Image.GetInstance(b1, BaseColor.WHITE);
                                    //Absolutely position the image
                                    img1.SetAbsolutePosition(0, 0);
                                    //Change the page size for the next page added to match the source image
                                    doc.SetPageSize(new iTextSharp.text.Rectangle(0, 0, b1.Width, b1.Height, 0));
                                    //Add a new page
                                    doc.NewPage();
                                    //Add the image directly to the writer
                                    writer.DirectContent.AddImage(img1);
                                }
                            }
                        }
                        //Repeat the above but with a larger and wider image
                        using (Bitmap b2 = new Bitmap(4000, 1000)) {
                            using (Graphics g2 = Graphics.FromImage(b2)) {
                                using (Pen p2 = new Pen(Color.Red, 10)) {
                                    p2.StartCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;
                                    p2.EndCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;
                                    g2.DrawLine(p2, 0, b2.Height / 2, b2.Width, b2.Height / 2);
                                    g2.DrawLine(p2, b2.Width / 2, 0, b2.Width / 2, b2.Height);
                                    iTextSharp.text.Image img2 = iTextSharp.text.Image.GetInstance(b2, BaseColor.WHITE);
                                    img2.SetAbsolutePosition(0, 0);
                                    doc.SetPageSize(new iTextSharp.text.Rectangle(0, 0, b2.Width, b2.Height, 0));
                                    doc.NewPage();
                                    writer.DirectContent.AddImage(img2);
                                }
                            }
                        }

                        doc.Close();
                    }
                }
            }
            this.Close();
        }
    }
}

尝试这样的方法来纠正您的问题

foreach (var image in images)
{
    iTextSharp.text.Image pic = iTextSharp.text.Image.GetInstance(image, System.Drawing.Imaging.ImageFormat.Jpeg);
    if (pic.Height > pic.Width)
    {
        //Maximum height is 800 pixels.
        float percentage = 0.0f;
        percentage = 700 / pic.Height;
        pic.ScalePercent(percentage * 100);
    }
    else
    {
        //Maximum width is 600 pixels.
        float percentage = 0.0f;
        percentage = 540 / pic.Width;
        pic.ScalePercent(percentage * 100);
    }
    pic.Border = iTextSharp.text.Rectangle.BOX;
    pic.BorderColor = iTextSharp.text.BaseColor.BLACK;
    pic.BorderWidth = 3f;
    document.Add(pic);
    document.NewPage();
}

您没有说明是向文档中添加一个图像，还是添加多个以随时更改页面大小，但调用ONLY会在NEXT页面上生效。

换句话说，类似这样的东西：

<%@ WebHandler Language="C#" Class="scaleDocToImageSize" %>
using System;
using System.Web;
using iTextSharp.text;
using iTextSharp.text.pdf;
public class scaleDocToImageSize : IHttpHandler {
  public void ProcessRequest (HttpContext context) {
    HttpServerUtility Server = context.Server;
    HttpResponse Response = context.Response;
    Response.ContentType = "application/pdf";
    string[] imagePaths = {"./Image15.png", "./Image19.png"};
    using (Document document = new Document()) {
      PdfWriter.GetInstance(document, Response.OutputStream);
      document.Open();
      document.Add(new Paragraph("Page 1"));
      foreach (string path in imagePaths) {
        string imagePath = Server.MapPath(path);
        Image img = Image.GetInstance(imagePath);
        var width = img.ScaledWidth 
          + document.RightMargin
          + document.LeftMargin
        ;
        var height = img.ScaledHeight
          + document.TopMargin
          + document.BottomMargin
        ;
        Rectangle r = width > PageSize.A4.Width || height > PageSize.A4.Height
          ? new Rectangle(width, height)
          : PageSize.A4
        ;
/*
 * you __MUST__ call SetPageSize() __BEFORE__ calling NewPage()
 * AND __BEFORE__ adding the image to the document
 */
        document.SetPageSize(r);
        document.NewPage();
        document.Add(img);
      }
    }
  }
  public bool IsReusable { get { return false; } }
}

上面的工作示例是在web环境中（.ashx HTTP处理程序），因此您需要将上面的Response.OutputStream替换为FileStream（来自代码片段）。显然，您也需要替换文件路径。