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 p)        {            // An empty bitmap which will hold the cropped image            Bitmap bmp = new Bitmap(p.Width, p.Height);            //using (Bitmap bmp = new Bitmap(p.Width, p.Height))            {                Graphics g = Graphics.FromImage(bmp);                // Draw the given area (p) of the source image                // at location 0,0 on the empty bitmap (bmp)                g.DrawImage(source, 0, 0, p, 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 p)        {            // An empty bitmap which will hold the cropped image            Bitmap bmp = new Bitmap(p.Width, p.Height);            //using (Bitmap bmp = new Bitmap(p.Width, p.Height))            {                Graphics g = Graphics.FromImage(bmp);                // Draw the given area (p) of the source image                // at location 0,0 on the empty bitmap (bmp)                g.DrawImage(source, 0, 0, p, 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; }        /// 
        /// 長邊縮到指定長度        /// 
        public int ResizeMaxWidth { get; set; }        public bool Wait { get; set; }    }}

效果

完成，达到预期的效果。