determine if file is an image

Question

I am looping through a directory and copying all files. Right now I am doing string.EndsWith checks for ".jpg" or ".png", etc . .

Is there a more elegant way of determining if a file is an image (any image type) without the hacky check above?

Answer 1

Check the file for a known header.

[Update: moving info out of comment]. The first eight bytes of a PNG file always contain the following (decimal) values: 137 80 78 71 13 10 26 10

Answer 2

Check out System.IO.Path.GetExtension

Here is a quick sample.

public static readonly List<string> ImageExtensions = new List<string> { ".JPG", ".JPE", ".BMP", ".GIF", ".PNG" };

private void button_Click(object sender, RoutedEventArgs e)
{
    var folder = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
    var files = Directory.GetFiles(folder);
    foreach(var f in files)
    {
        if (ImageExtensions.Contains(Path.GetExtension(f).ToUpperInvariant()))
        {
            // process image
        }
    }
}

Answer 3

See if this helps.

EDIT: Also, Image.FromFile(....).RawFormat might help. It could throw an exception if the file is not an image.

Answer 4

Not exactly the answer you need. But if it’s the Internet then MIME type.