FileSystem Watcher- Checking if copied file is an Image

Question

I'm monitoring a Folder for File creation(Copied) event using FileSystem Watcher. I only want the program to process image Files.

FileSystemWatcher watcher = new FileSystemWatcher();
watcher.Filter = "*.*";
watcher.Created += new FileSystemEventHandler(watcher_FileCreated);
watcher.Path = path;

So I try to create a Bitmap and avoid the file if an exception is thrown

private static void watcher_FileCreated(object sender, FileSystemEventArgs e)
{
    try
    {
        using (Bitmap test = new Bitmap(Bitmap.FromFile(e.FullPath)))
        {
            mytoprocesslist.add(e.FullPath);
        }

        //do my processing with image 
        Console.WriteLine(e.FullPath);
    }
    catch (Exception error)
    {
       Console.WriteLine("File Error");
    }
 }

This throws Out of Memory exception even when a valid image file is copied, which I think happens because the event was raised before the file was copied completely. How can I get over this? I only want to add the valid image files to a to do list and I will process these images one by one later.

Answer 1

A bit cleaner solution than a Try-Catch might be this one. Im using this code without any exceptions raised.

private static bool IsImage(string path) {
      try {
        var result = false;

        using (var stream = new FileStream(path, FileMode.Open)) {
          stream.Seek(0, SeekOrigin.Begin);

          var jpg = new List<string> { "FF", "D8" };
          var bmp = new List<string> { "42", "4D" };
          var gif = new List<string> { "47", "49", "46" };
          var png = new List<string> { "89", "50", "4E", "47", "0D", "0A", "1A", "0A" };
          var imgTypes = new List<List<string>> { jpg, bmp, gif, png };

          var bytesIterated = new List<string>();

          for (var i = 0; i < 8; i++) {
            var bit = stream.ReadByte().ToString("X2");
            bytesIterated.Add(bit);

            var isImage = imgTypes.Any(img => !img.Except(bytesIterated).Any());
            if (isImage) {
              result = true;
              break;
            }
          }
        }
        return result;
      } catch (UnauthorizedAccessException) {
        return false;
      }
    }

Usage of code

foreach (var file in Directory.EnumerateFiles(@"pathToFlowersFolder"))
            {
                Console.WriteLine($"File: {file} Result:{IsImage(file)}");
            }

Edit

After playing around i got an IO-Exception (File already in use)
After reading this i'd offer you the following solution:

private void button1_Click(object sender, EventArgs e)
        {
            var watcher = new FileSystemWatcher();
            watcher.Created += new FileSystemEventHandler(fileSystemWatcher1_Changed);
            watcher.Path = @"c:\temp";
            watcher.NotifyFilter = NotifyFilters.FileName | NotifyFilters.Size;
            watcher.EnableRaisingEvents = true;
        }

        private void fileSystemWatcher1_Changed(object sender, System.IO.FileSystemEventArgs e)
        {
            Thread.Sleep(100); // <- give the Creator some time. Increase value for greate pause
            if (IsImage(e.FullPath))
            {
                Console.WriteLine("success----------->" + e.FullPath);
            }
        }

Note

This piece of code properly works on my machine. My HDD is an SSD, so you might need to increase the thread-sleeping time. It properly works for all images (jpg, bmp, gif, png) up to a size of 7 Mb (im quite sure and greater).

If this code doesnt works for you, please post the exception rather than uploading your code.

Answer 2

For the first requirement: "I only want the program to process image files"

private static void fileSystemWatcher1_Changed(object sender, FileSystemEventArgs e)
{
  string strFileExt = getFileExt(e.FullPath); 

  // filter file types 
  if (Regex.IsMatch(strFileExt, @"\.png|\.jpg", RegexOptions.IgnoreCase)) 
  { 
      //here Process the image file 
  }
} 

For the second requirement: "Out of Memory Exception"

Here what happens is, when the file is created (only file name and some attributes) the system is calling the created event. Then the file changed event is also called

So you have to do the processing in the changed event. Also to prevent duplicate calling you have to add a filter to your watcher.

The following is the complete code.

private void fileSystemWatcher1_Changed(object sender, System.IO.FileSystemEventArgs e)
        {

            FileInfo fileInfo = new FileInfo(e.FullPath);
            string strFileExt = fileInfo.Extension;

            // filter file types 
            if (Regex.IsMatch(strFileExt, @"\.png|\.jpg", RegexOptions.IgnoreCase))
            {
                //here Process the image file 
                try
                {
                    using (Bitmap test = new Bitmap(Bitmap.FromFile(e.FullPath)))
                    {
                        //Do your code here.
                    }
                }
                catch (Exception error)
                {
                    Console.WriteLine("File Error");
                }
            }


        }

        private void Form1_Load(object sender, EventArgs e)
        {
            fileSystemWatcher1.Path = @"C:\Users\Christlin\Desktop\res";

            //To Prevent duplicated calling of changed event
            fileSystemWatcher1.NotifyFilter = NotifyFilters.FileName | NotifyFilters.Size;
        }