c# 实现网页加载后将页面截取为长图片

背景

最近再做一个需求，需要对网页生成预览图，如下图

但是网页千千万，总不能一个个打开，截图吧；于是想着能不能使用代码来实现网页的截图。其实要实现这个功能，无非就是要么实现一个仿真浏览器，要么调用系统浏览器，再进行截图操作。

代码实现

1、启用线程Thread

void startPrintScreen(ScreenShotParam requestParam)
  {
   Thread thread = new Thread(new ParameterizedThreadStart(do_PrintScreen));
   thread.SetApartmentState(ApartmentState.STA);
   thread.Start(requestParam);
   if (requestParam.Wait)
   {
    thread.Join();
    FileInfo result = new FileInfo(requestParam.SavePath);
    long minSize = 1 * 1024;// 太小可能是空白圖，重抓
    int maxRepeat = 2;
    while ((!result.Exists || result.Length <= minSize) && maxRepeat > 0)
    {
     thread = new Thread(new ParameterizedThreadStart(do_PrintScreen));
     thread.SetApartmentState(ApartmentState.STA);
     thread.Start(requestParam);
     thread.Join();
     maxRepeat--;
    }
   }
  }

2、模拟浏览器WebBrowser

void do_PrintScreen(object param)
  {
   try
   {
    ScreenShotParam screenShotParam = (ScreenShotParam)param;
    string requestUrl = screenShotParam.Url;
    string savePath = screenShotParam.SavePath;
    WebBrowser wb = new WebBrowser();
    wb.ScrollBarsEnabled = false;
    wb.ScriptErrorsSuppressed = true;
    wb.Navigate(requestUrl);
    logger.Debug("wb.Navigate");
    DateTime startTime = DateTime.Now;
    TimeSpan waitTime = new TimeSpan(0, 0, 0, 10, 0);// 10 second
    while (wb.ReadyState != WebBrowserReadyState.Complete)
    {
     Application.DoEvents();
     if (DateTime.Now - startTime > waitTime)
     {
      wb.Dispose();
      logger.Debug("wb.Dispose() timeout");
      return;
     }
    }

    wb.Width = screenShotParam.Left + screenShotParam.Width + screenShotParam.Left; // wb.Document.Body.ScrollRectangle.Width (避掉左右側的邊線);
    wb.Height = screenShotParam.Top + screenShotParam.Height; // wb.Document.Body.ScrollRectangle.Height;
    wb.ScrollBarsEnabled = false;
    wb.Document.Body.Style = "overflow:hidden";//hide scroll bar
    var doc = (wb.Document.DomDocument) as mshtml.IHTMLDocument2;
    var style = doc.createStyleSheet("", 0);
    style.cssText = @"img { border-style: none; }";

    Bitmap bitmap = new Bitmap(wb.Width, wb.Height);
    wb.DrawToBitmap(bitmap, new Rectangle(0, 0, wb.Width, wb.Height));
    wb.Dispose();
    logger.Debug("wb.Dispose()");

    bitmap = CutImage(bitmap, new Rectangle(screenShotParam.Left, screenShotParam.Top, screenShotParam.Width, screenShotParam.Height));
    bool needResize = screenShotParam.Width > screenShotParam.ResizeMaxWidth || screenShotParam.Height > screenShotParam.ResizeMaxWidth;
    if (needResize)
    {
     double greaterLength = bitmap.Width > bitmap.Height ? bitmap.Width : bitmap.Height;
     double ratio = screenShotParam.ResizeMaxWidth / greaterLength;
     bitmap = Resize(bitmap, ratio);
    }

    bitmap.Save(savePath, System.Drawing.Imaging.ImageFormat.Gif);
    bitmap.Dispose();
    logger.Debug("bitmap.Dispose();");
    logger.Debug("finish");

   }
   catch (Exception ex)
   {
    logger.Info($"exception: {ex.Message}");
   }
  }

3、截图操作

private static Bitmap CutImage(Bitmap source, Rectangle section)
  {
   // An empty bitmap which will hold the cropped image
   Bitmap bmp = new Bitmap(section.Width, section.Height);
   //using (Bitmap bmp = new Bitmap(section.Width, section.Height))
   {
    Graphics g = Graphics.FromImage(bmp);

    // Draw the given area (section) of the source image
    // at location 0,0 on the empty bitmap (bmp)
    g.DrawImage(source, 0, 0, section, GraphicsUnit.Pixel);

    return bmp;
   }
  }

  private static Bitmap Resize(Bitmap originImage, Double times)
  {
   int width = Convert.ToInt32(originImage.Width * times);
   int height = Convert.ToInt32(originImage.Height * times);

   return ResizeProcess(originImage, originImage.Width, originImage.Height, width, height);
  }

完整代码

public static string ScreenShotAndSaveAmazonS3(string account, string locale, Guid rule_ID, Guid template_ID)
  {

   //新的Template
   var url = string.Format("https://xxxx/public/previewtemplate?showTemplateName=0&locale={0}&inputTemplateId={1}&inputThemeId=&Account={2}",
    locale,
    template_ID,
    account
    );

   var tempPath = Tools.GetAppSetting("TempPath");

   //路徑準備
   var userPath = AmazonS3.GetS3UploadDirectory(account, locale, AmazonS3.S3SubFolder.Template);
   var fileName = string.Format("{0}.gif", template_ID);
   var fullFilePath = Path.Combine(userPath.LocalDirectoryPath, fileName);
   logger.Debug("userPath: {0}, fileName: {1}, fullFilePath: {2}, url:{3}", userPath, fileName, fullFilePath, url);

   //開始截圖，並暫存在本機
   var screen = new Screen();
   screen.ScreenShot(url, fullFilePath);

   //將截圖，儲存到 Amazon S3
   //var previewImageUrl = AmazonS3.UploadFile(fullFilePath, userPath.RemotePath + fileName);

   return string.Empty;
  }

using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace PrintScreen.Common
{
 public class Screen
 {
  protected static NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger();

  public void ScreenShot(string url, string path
   , int width = 400, int height = 300
   , int left = 50, int top = 50
   , int resizeMaxWidth = 200, int wait = 1)
  {
   if (!string.IsNullOrEmpty(url) && !string.IsNullOrEmpty(path))
   {
    ScreenShotParam requestParam = new ScreenShotParam
    {
     Url = url,
     SavePath = path,
     Width = width,
     Height = height,
     Left = left,
     Top = top,
     ResizeMaxWidth = resizeMaxWidth,
     Wait = wait != 0
    };
    startPrintScreen(requestParam);
   }
  }

  void startPrintScreen(ScreenShotParam requestParam)
  {
   Thread thread = new Thread(new ParameterizedThreadStart(do_PrintScreen));
   thread.SetApartmentState(ApartmentState.STA);
   thread.Start(requestParam);
   if (requestParam.Wait)
   {
    thread.Join();
    FileInfo result = new FileInfo(requestParam.SavePath);
    long minSize = 1 * 1024;// 太小可能是空白圖，重抓
    int maxRepeat = 2;
    while ((!result.Exists || result.Length <= minSize) && maxRepeat > 0)
    {
     thread = new Thread(new ParameterizedThreadStart(do_PrintScreen));
     thread.SetApartmentState(ApartmentState.STA);
     thread.Start(requestParam);
     thread.Join();
     maxRepeat--;
    }
   }
  }

  void do_PrintScreen(object param)
  {
   try
   {
    ScreenShotParam screenShotParam = (ScreenShotParam)param;
    string requestUrl = screenShotParam.Url;
    string savePath = screenShotParam.SavePath;
    WebBrowser wb = new WebBrowser();
    wb.ScrollBarsEnabled = false;
    wb.ScriptErrorsSuppressed = true;
    wb.Navigate(requestUrl);
    logger.Debug("wb.Navigate");
    DateTime startTime = DateTime.Now;
    TimeSpan waitTime = new TimeSpan(0, 0, 0, 10, 0);// 10 second
    while (wb.ReadyState != WebBrowserReadyState.Complete)
    {
     Application.DoEvents();
     if (DateTime.Now - startTime > waitTime)
     {
      wb.Dispose();
      logger.Debug("wb.Dispose() timeout");
      return;
     }
    }

    wb.Width = screenShotParam.Left + screenShotParam.Width + screenShotParam.Left; // wb.Document.Body.ScrollRectangle.Width (避掉左右側的邊線);
    wb.Height = screenShotParam.Top + screenShotParam.Height; // wb.Document.Body.ScrollRectangle.Height;
    wb.ScrollBarsEnabled = false;
    wb.Document.Body.Style = "overflow:hidden";//hide scroll bar
    var doc = (wb.Document.DomDocument) as mshtml.IHTMLDocument2;
    var style = doc.createStyleSheet("", 0);
    style.cssText = @"img { border-style: none; }";

    Bitmap bitmap = new Bitmap(wb.Width, wb.Height);
    wb.DrawToBitmap(bitmap, new Rectangle(0, 0, wb.Width, wb.Height));
    wb.Dispose();
    logger.Debug("wb.Dispose()");

    bitmap = CutImage(bitmap, new Rectangle(screenShotParam.Left, screenShotParam.Top, screenShotParam.Width, screenShotParam.Height));
    bool needResize = screenShotParam.Width > screenShotParam.ResizeMaxWidth || screenShotParam.Height > screenShotParam.ResizeMaxWidth;
    if (needResize)
    {
     double greaterLength = bitmap.Width > bitmap.Height ? bitmap.Width : bitmap.Height;
     double ratio = screenShotParam.ResizeMaxWidth / greaterLength;
     bitmap = Resize(bitmap, ratio);
    }

    bitmap.Save(savePath, System.Drawing.Imaging.ImageFormat.Gif);
    bitmap.Dispose();
    logger.Debug("bitmap.Dispose();");
    logger.Debug("finish");

   }
   catch (Exception ex)
   {
    logger.Info($"exception: {ex.Message}");
   }
  }

  private static Bitmap CutImage(Bitmap source, Rectangle section)
  {
   // An empty bitmap which will hold the cropped image
   Bitmap bmp = new Bitmap(section.Width, section.Height);
   //using (Bitmap bmp = new Bitmap(section.Width, section.Height))
   {
    Graphics g = Graphics.FromImage(bmp);

    // Draw the given area (section) of the source image
    // at location 0,0 on the empty bitmap (bmp)
    g.DrawImage(source, 0, 0, section, GraphicsUnit.Pixel);

    return bmp;
   }
  }

  private static Bitmap Resize(Bitmap originImage, Double times)
  {
   int width = Convert.ToInt32(originImage.Width * times);
   int height = Convert.ToInt32(originImage.Height * times);

   return ResizeProcess(originImage, originImage.Width, originImage.Height, width, height);
  }

  private static Bitmap ResizeProcess(Bitmap originImage, int oriwidth, int oriheight, int width, int height)
  {
   Bitmap resizedbitmap = new Bitmap(width, height);
   //using (Bitmap resizedbitmap = new Bitmap(width, height))
   {
    Graphics g = Graphics.FromImage(resizedbitmap);
    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
    g.Clear(Color.Transparent);
    g.DrawImage(originImage, new Rectangle(0, 0, width, height), new Rectangle(0, 0, oriwidth, oriheight), GraphicsUnit.Pixel);
    return resizedbitmap;
   }
  }

 }

 class ScreenShotParam
 {
  public string Url { get; set; }
  public string SavePath { get; set; }
  public int Width { get; set; }
  public int Height { get; set; }
  public int Left { get; set; }
  public int Top { get; set; }
  /// <summary>
  /// 長邊縮到指定長度
  /// </summary>
  public int ResizeMaxWidth { get; set; }
  public bool Wait { get; set; }
 }

}

效果

以上就是c# 实现网页加载后将页面截取为长图片的详细内容，更多关于c# 页面截取为图片的资料请关注我们其它相关文章！