HTML轉(zhuǎn)PDF（C#---itextsharp）

HTML轉(zhuǎn)PDF（C#---itextsharp）

一、 需求：將HTML轉(zhuǎn)PDF打印。Web項目中總是有這樣的需求，很是讓人苦惱。
二、 分析：如何完成這個工作？
1、 需要解析HTML，然后利用itextsharp繪制pdf文檔。解析HTML是一個很難完成的任務(wù)，各個瀏覽器對HTML的解析五花八門就知道這不好解決。這條路不好走，但也是可以完成的，通過webbrowser類可以解析HTML獲取各對象的位置，然后繪制到pdf中。方法是可行，其中的復雜度不小。
2、 將HTML保存為圖片，然后插入到pdf文檔中，這里將介紹這種方法。隨之而來的問題：如何將HTML保存為圖片呢？
三、 解決辦法：
1、 將HTML保存為圖片：需要用到webbrower類，將指定的HTML載入webbrower，然后調(diào)用其DrawToBitmap方法獲取圖片。代碼如下：
private System.Drawing.Bitmap bitmap;
??? private string url;
??? private int w = 760, h = 900;//A4紙張對應(yīng)的分辨率大概就是760*900
??? public void setBitmap()
??? {
??????? using (WebBrowser wb = new WebBrowser())
??????? {
??????????? wb.Width = w;
??????????? wb.Height = h;
??????????? wb.ScrollBarsEnabled = false;
??????????? wb.Navigate(url);
??????????? //確保頁面被解析完全
??????????? while (wb.ReadyState != WebBrowserReadyState.Complete)
??????????? {
??????????????? System.Windows.Forms.Application.DoEvents();
??????????? }
??????????? bitmap = new System.Drawing.Bitmap(w, h);
??????????? wb.DrawToBitmap(bitmap, new System.Drawing.Rectangle(0, 0, w, h));
??????????? wb.Dispose();
??????? }
??? }
2、 如何調(diào)用WebBrowser？直接在web頁面用的話，會出現(xiàn)錯誤：“當前線程不在單線程單元中,因此無法實例化 ActiveX 控件”。這需要創(chuàng)建一個單線程單元，在此單元內(nèi)調(diào)用，方法如下while循環(huán)確保線程執(zhí)行完成，也就是確保bitmap已經(jīng)被初始化了：
??????????? url = Server.MapPath("s.html");
??????????? Thread thread = new Thread(new ThreadStart(setBitmap));
??????????? thread.SetApartmentState(ApartmentState.STA);
??????????? thread.Start();
??????????? while (thread.IsAlive)
??????????????? Thread.Sleep(100);
??????????? bitmap.Save(Server.MapPath("t.bmp"));
3、 插入圖片到PDF：
iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(bitmap, System.Drawing.Imaging.ImageFormat.Bmp);
??????????? img.ScalePercent(75);//pdf分辨率要大一些，需要縮小以恢復正常PDF是96DPI，IE是72DPI
??????????? doc.Add(img);
四、 完整代碼如下：
using System;
using System.Data;
using System.Web;
using iTextSharp.text.pdf;
using iTextSharp.text;
using System.IO;
using System.Windows.Forms;
using System.Threading;
public partial class HTML2PDF : System.Web.UI.Page
{
??? protected void Page_Load(object sender, EventArgs e)
??? {

??? }
??? protected void Button1_Click(object sender, EventArgs e)
??? {
??????? CreatPdf();
??? }
??? private System.Drawing.Bitmap bitmap;
??? private string url;
??? private int w = 760, h = 900;
??? public void setBitmap()
??? {
??????? using (WebBrowser wb = new WebBrowser())
??????? {
??????????? wb.Width = w;
??????????? wb.Height = h;
??????????? wb.ScrollBarsEnabled = false;
??????????? wb.Navigate(url);
??????????? //確保頁面被解析完全
??????????? while (wb.ReadyState != WebBrowserReadyState.Complete)
??????????? {
??????????????? System.Windows.Forms.Application.DoEvents();
??????????? }
??????????? bitmap = new System.Drawing.Bitmap(w, h);
??????????? wb.DrawToBitmap(bitmap, new System.Drawing.Rectangle(0, 0, w, h));
??????????? wb.Dispose();
??????? }
??? }
??? private void CreatPdf()
??? {
??????? Document doc = new Document(PageSize.A4, 9, 18, 36, 36);//左右上下
??????? MemoryStream ms = new MemoryStream();
??????? try
??????? {
??????????? PdfWriter writer = PdfWriter.GetInstance(doc, ms);
??????????? writer.CloseStream = false;
??????????? doc.Open();
??????????? url = Server.MapPath("s.html");
??????????? Thread thread = new Thread(new ThreadStart(setBitmap));
??????????? thread.SetApartmentState(ApartmentState.STA);
??????????? thread.Start();
??????????? while (thread.IsAlive)
??????????????? Thread.Sleep(100);
??????????? bitmap.Save(Server.MapPath("t.bmp"));
????????????
??????????? iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(bitmap, System.Drawing.Imaging.ImageFormat.Bmp);
??????????? img.ScalePercent(75);//560 630
??????????? doc.Add(img);
??????? }
??????? catch (Exception err)
??????? {
??????????? throw new Exception(err.Message);
??????? }
??????? finally
??????? {
??????????? doc.Close();
??????????? using (FileStream fs = new FileStream(Server.MapPath("out.pdf"), FileMode.Create))
??????????? {
??????????????? ms.Position = 0;
??????????????? byte[] bit = new byte[ms.Length];
??????????????? ms.Read(bit, 0, (int)ms.Length);
??????????????? fs.Write(bit, 0, bit.Length);
??????????? }
??????????? ViewPdf(ms);
??????? }
??? }

??? private void ViewPdf(Stream fs)
??? {
??????? Response.Clear();
??????? //中文名的話
??????? //Response.AppendHeader("Content-Disposition", "attachment;filename=" +
??????? //???????????? HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8) + ";charset=GB2312");
??????? Response.AddHeader("Content-Disposition", "attachment;FileName=out.pdf");
??????? Response.AddHeader("Content-Length", fs.Length.ToString());
??????? Response.ContentType = "application/pdf";
??????? long fileLength = fs.Length;
??????? int size = 10240;//10K一--分塊下載，10K為1塊
??????? byte[] readData = new byte[size];
??????? if (size > fileLength)
??????????? size = Convert.ToInt32(fileLength);
??????? long fPos = 0;
??????? bool isEnd = false;
??????? while (!isEnd)
??????? {
??????????? if ((fPos + size) >= fileLength)
??????????? {
??????????????? size = Convert.ToInt32(fileLength - fPos);
??????????????? isEnd = true;
??????????? }
??????????? readData = new byte[size];
??????????? fs.Position = fPos;
??????????? fs.Read(readData, 0, size);
??????????? Response.BinaryWrite(readData);
??????????? Response.OutputStream.Flush();
??????????? fPos += size;
??????? }
??????? fs.Close();
??????? Response.OutputStream.Close();
??????? Response.End();//非常重要，沒有這句的話，頁面的HTML代碼將會保存到文件中
??????? Response.Close();
??? }
}

五、至此工作完成，轉(zhuǎn)載注明出處，謝謝。

六、2009-12-23補充說明：增加pdf打印清晰度，對于圖片，要想在pdf上打印的更清晰需要生成大圖，然后等比例縮放存放在pdf里面，這樣pdf打印出來的圖會很清晰，基本是縮放比例越大越清晰，對于圖形報表特別有效。對于本文介紹的方法，也可以生成大圖縮放到pdf里面。

轉(zhuǎn)載于:https://www.cnblogs.com/-yxy/archive/2013/04/23/3038582.html

與50位技術(shù)專家面對面20年技術(shù)見證，附贈技術(shù)全景圖

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