Get ImageFormat from File Extension

Question

Is there quick way to get the ImageFormat object associated to a particular file extension? I'm looking for quicker than string comparisons for each format.

richardtallent · Accepted Answer · 2020-06-07T22:48:19.067

35

Here's some old code I found that should do the trick:

 var inputSource = "mypic.png";
 var imgInput = System.Drawing.Image.FromFile(inputSource);
 var thisFormat = imgInput.RawFormat;

This requires actually opening and testing the image--the file extension is ignored. Assuming you are opening the file anyway, this is much more robust than trusting a file extension.

If you aren't opening the files, there's nothing "quicker" (in a performance sense) than a string comparison--certainly not calling into the OS to get file extension mappings.

edited Jun 07 '20 at 22:48

answered Aug 26 '09 at 22:04

richardtallent

34,724
14
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5

Why do you need the line `Graphics gInput = Graphics.FromImage(imgInput);`? `gInput` is not used at all. – Tim Schmelter Sep 25 '14 at 08:15
Maybe, he wanted to put all this in a Try-Catch and see if it works. – RealityDysfunction Oct 08 '14 at 15:58
This is rather useless for a "save as..." scenario, though. – Nyerguds Feb 26 '15 at 09:55
@TimSchmelter, good point, I've removed the extra call. It was there because this came from production code where I was using the image after detecting the type. – richardtallent Jun 07 '20 at 22:49

score 35 · Answer 2 · answered Nov 23 '12 at 05:30

private static ImageFormat GetImageFormat(string fileName)
{
    string extension = Path.GetExtension(fileName);
    if (string.IsNullOrEmpty(extension))
        throw new ArgumentException(
            string.Format("Unable to determine file extension for fileName: {0}", fileName));

    switch (extension.ToLower())
    {
        case @".bmp":
            return ImageFormat.Bmp;

        case @".gif":
            return ImageFormat.Gif;

        case @".ico":
            return ImageFormat.Icon;

        case @".jpg":
        case @".jpeg":
            return ImageFormat.Jpeg;

        case @".png":
            return ImageFormat.Png;

        case @".tif":
        case @".tiff":
            return ImageFormat.Tiff;

        case @".wmf":
            return ImageFormat.Wmf;

        default:
            throw new NotImplementedException();
    }
}

This is the better option if opening the file isn't possible. For example, loading a very large image may cause an `OutOfMemory` exception. This isn't as robust, will do for many use-cases. — TEK, May 09 '16 at 15:56

score 4 · Answer 3 · answered Nov 10 '14 at 14:32

4

    private static ImageFormat GetImageFormat(string format)
    {
        ImageFormat imageFormat = null;

        try
        {
            var imageFormatConverter = new ImageFormatConverter();
            imageFormat = (ImageFormat)imageFormatConverter.ConvertFromString(format);
        }
        catch (Exception)
        {

            throw;
        }

        return imageFormat;
    }

answered Nov 10 '14 at 14:32

Barda

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I don't understand why this is upvoted! imageFormatConverter.ConvertFromString is inherited from TypeConverter and always returns null or throws a NotSupportedException! [see this](https://stackoverflow.com/a/3594313/2803565) – S.Serpooshan Dec 10 '17 at 11:45

score 1 · Answer 4 · answered Aug 26 '09 at 22:02

1

see the CodeProject article on File Associations http://www.codeproject.com/KB/dotnet/System_File_Association.aspx

answered Aug 26 '09 at 22:02

Robert French

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Get ImageFormat from File Extension

4 Answers4

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