get extension from System.Drawing.Imaging.ImageFormat (C#)

Question

Is it possible to get the extension, for any given System.Drawing.Imaging.ImageFormat? (C#)

Example:

System.Drawing.Imaging.ImageFormat.Tiff -> .tif
System.Drawing.Imaging.ImageFormat.Jpeg -> .jpg
...

This can easily be done as a lookup table, but wanted to know if there is anything natively in .Net.

Answer 1

I have now found 3 ways to do this, of which, the last 2 are equivalent. All are extension methods and intend to produce an extension in the form ".foo"

static class ImageFormatUtils
{
    //Attempt 1: Use ImageCodecInfo.GetImageEncoders
    public static string FileExtensionFromEncoder(this ImageFormat format)
    {
        try
        {
            return ImageCodecInfo.GetImageEncoders()
                    .First(x => x.FormatID == format.Guid)
                    .FilenameExtension
                    .Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries)
                    .First()
                    .Trim('*')
                    .ToLower();
        }
        catch (Exception)
        {
            return ".IDFK";
        }
    }

    //Attempt 2: Using ImageFormatConverter().ConvertToString()
    public static string FileExtensionFromConverter(this ImageFormat format)
    {
        return "." + new ImageFormatConverter().ConvertToString(format).ToLower();
    }

    //Attempt 3: Using ImageFormat.ToString()
    public static string FileExtensionFromToString(this ImageFormat format)
    {
        return "." + format.ToString().ToLower();
    }
}

Being extension methods they can be called like:

ImageFormat format = ImageFormat.Jpeg;
var filePath = "image" + format.FileExtensionFromEncoder();

The resulting string will be:

"image.jpg"

To compare these new methods I made a short console app:

class Program
{
    static void Main()
    {
        var formats = new[]
        {
            ImageFormat.Bmp, ImageFormat.Emf, ImageFormat.Exif, ImageFormat.Gif,
            ImageFormat.Icon, ImageFormat.Jpeg, ImageFormat.MemoryBmp, ImageFormat.Png,
            ImageFormat.Tiff, ImageFormat.Wmf
        };

        foreach (var format in formats)
        {
            Console.WriteLine("FromEncoder: '{0}', FromConverter: '{1}', FromToString: '{2}'", format.FileExtensionFromEncoder(), format.FileExtensionFromConverter(), format.FileExtensionFromToString());
        }
        Console.Read();
    }
}

Running this results in the following output:

FromEncoder: '.bmp', FromConverter: '.bmp', FromToString: '.bmp'
FromEncoder: '.IDFK', FromConverter: '.emf', FromToString: '.emf'
FromEncoder: '.IDFK', FromConverter: '.exif', FromToString: '.exif'
FromEncoder: '.gif', FromConverter: '.gif', FromToString: '.gif'
FromEncoder: '.IDFK', FromConverter: '.icon', FromToString: '.icon'
FromEncoder: '.jpg', FromConverter: '.jpeg', FromToString: '.jpeg'
FromEncoder: '.IDFK', FromConverter: '.memorybmp', FromToString: '.memorybmp'
FromEncoder: '.png', FromConverter: '.png', FromToString: '.png'
FromEncoder: '.tif', FromConverter: '.tiff', FromToString: '.tiff'
FromEncoder: '.IDFK', FromConverter: '.wmf', FromToString: '.wmf'

You can see that the original method fails and produces a '.IDFK' on the more obscure formats while the other methods are actually just using the name of the format; ImageFormat.Jpeg, '.jpeg'; ImageFormat.MemoryBmp, '.memorybmp'; etc..

So as the original question wants '.tif' rather then '.tiff', it would seem the first method is for you. Or maybe some combination of the 2 would be ideal:

    public static string FileExtensionFromEncoder(this ImageFormat format)
    {
        try
        {
            return ImageCodecInfo.GetImageEncoders()
                    .First(x => x.FormatID == format.Guid)
                    .FilenameExtension
                    .Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries)
                    .First()
                    .Trim('*')
                    .ToLower();
        }
        catch (Exception)
        {
            return "." + format.ToString().ToLower();
        }
    }

Answer 2

mayby this is what you are looking for?

    public static string GetFilenameExtension(ImageFormat format)
    {
        return ImageCodecInfo.GetImageEncoders().FirstOrDefault(x => x.FormatID == format.Guid).FilenameExtension;
    }

Answer 3

Kevin Bray's answer is great. I wasn't 100% happy with relying on catching an exception in this way though, so I tweaked his solution very slightly...

public static string GetFileExtension(this ImageFormat imageFormat)
{
    var extension = ImageCodecInfo.GetImageEncoders()
        .Where(ie => ie.FormatID == imageFormat.Guid)
        .Select(ie => ie.FilenameExtension
            .Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries)
            .First()
            .Trim('*')
            .ToLower())
        .FirstOrDefault();

    return extension ?? string.Format(".{0}", imageFormat.ToString().ToLower());
}