Reading metadata from images in WPF

Question

I\'m aware that WPF allows you to use images that require WIC codecs to view (for the sake of argument, say a digital camera RAW file); however I can only see that it lets y

Answer 1

Check out my Intuipic project. In particular, the BitmapOrientationConverter class, which reads metadata to determine the image's orientation:

private const string _orientationQuery = "System.Photo.Orientation";
...

using (FileStream fileStream = new FileStream(path, FileMode.Open, FileAccess.Read))
{
    BitmapFrame bitmapFrame = BitmapFrame.Create(fileStream, BitmapCreateOptions.DelayCreation, BitmapCacheOption.None);
    BitmapMetadata bitmapMetadata = bitmapFrame.Metadata as BitmapMetadata;

    if ((bitmapMetadata != null) && (bitmapMetadata.ContainsQuery(_orientationQuery)))
    {
        object o = bitmapMetadata.GetQuery(_orientationQuery);

        if (o != null)
        {
            //refer to http://www.impulseadventure.com/photo/exif-orientation.html for details on orientation values
            switch ((ushort) o)
            {
                case 6:
                    return 90D;
                case 3:
                    return 180D;
                case 8:
                    return 270D;
            }
        }
    }
}

Answer 2

Whilst WPF does provide these APIs, they're not very friendly and they're not particularly fast. I suspect they're doing a lot of interop.

I maintain a simple open-source library for extracting metadata from images and videos. It's 100% C# with no P/Invoke.

// Read all metadata from the image
var directories = ImageMetadataReader.ReadMetadata(stream);

// Find the so-called Exif "SubIFD" (which may be null)
var subIfdDirectory = directories.OfType<ExifSubIfdDirectory>().FirstOrDefault();

// Read the orientation
var orientation = subIfdDirectory?.GetInt(ExifDirectoryBase.TagOrientation);

switch (orientation)
{
    case 6:
        return 90D;
    case 3:
        return 180D;
    case 8:
        return 270D;
}

In my benchmarks, this is 17 times faster than the WPF API. If you only want Exif from JPEG, use the following and it's over 30 times faster:

var directories = JpegMetadataReader.ReadMetadata(stream, new[] { new ExifReader() });

The metadata-extractor library is available via NuGet and the code's on GitHub.

Credit is due to the many contributors who've helped the project since it started in 2002.