最近在做一个需求，需要对网页生成预览图。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。

C#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);
 }

4、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.IsOrEmpty(url) && !string.IsOrEmpty(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; }
 }

}

5、实现效果