Exif Rational[] for GPSLongitude

[AndyWorral]

Hello,

I'm trying to figure out exactly how the Rational[] works with Latitude/Longitude.

I have an image I took with my phone with a Longitude of 78.764446. If I load the image into ImageSharp I get an array that looks like

(from LinqPad output)

If I save that image back to hard drive it is fine, and using and Exif Viewer the data is correct. When I am trying to set the longitude myself on a different photo I am just creating a new Rational[] { Rational.FromDouble(78.764446) }; This seems to also work when I save it, however I don't follow what happening with the original photo loading with the array and how it has two Whole numbers 78/1 and 45/1 in the array. The FromDouble when I call it looks a lot different.

Thanks!

[JimBobSquarePants]

Those 3 rational numbers represent a geographic location in sexagesimal degree units of degrees, minutes, and seconds

If you add this code to your LinqPad output

// degrees + (minutes / 60) + (seconds /3600)
(78 + (45 / 60D) + ((52004642 / 1000000D) / 3600D)).Dump();

You get the answer 78.76444573388889 which matches your input to 6 decimal places.

When you use a single rational in your array is it interpreted as a single decimal value.

[stamminator]

@JimBobSquarePants Just my opinion, but I think code snippets like this are so helpful that they'd be great to see in something like a Metadata Cookbook in the Wiki or as a helper method in the package.

static double? GetExifLatitude(ImageMetadata metadata)
{
    if (metadata.ExifProfile?.TryGetValue(ExifTag.GPSLatitude, out IExifValue<Rational[]>? latitudeParts) == true && latitudeParts?.Value?.Length == 3)
    {
        uint degrees = latitudeParts.Value[0].Numerator;
        double minutes = latitudeParts.Value[1].Numerator / 60D;
        double seconds = (latitudeParts.Value[2].Numerator / (double)latitudeParts.Value[2].Denominator) / 3600D;
        return degrees + minutes + seconds;
    }

    return null;
}