Write EXIF DateTimeOriginal example, please

[GF-Huang]

How to do that?

[JimBobSquarePants]

Hi @GF-Huang here's an example.

using (var image = new Image<Rgba32>(100, 100))
{
    // Create a new profile, since we crated the image.
    image.Metadata.ExifProfile = new ExifProfile();

    const string format = "yyyy:MM:dd HH:mm:ss";
    var now = DateTime.Now;
    var dt = now.ToString(format);

    // Set the metadata value.
    image.Metadata.ExifProfile.SetValue(ExifTag.DateTimeOriginal, dt);

    // Get the value.
    var dt2 = image.Metadata.ExifProfile.GetValue(ExifTag.DateTimeOriginal).Value;
    DateTime.TryParseExact(dt2, format, CultureInfo.InvariantCulture, DateTimeStyles.AssumeLocal, out DateTime now2);
}

https://docs.sixlabors.com/api/ImageSharp/SixLabors.ImageSharp.Metadata.Profiles.Exif.ExifTag.html?q=DateTimeOriginal

@dlemstra I wonder.... date and times are always formatted in the same way yeah? Should we provide an abstraction that allows direct get/set of DateTime instances, having to parse is pretty ugly.

[dlemstra]

We could probably introduce an ExifDateTime ExifValue to handle this and do the conversion to and from string there. I do wonder what the timezone of that DateTime object should be though.

[JimBobSquarePants]

There's a TimeZoneOffset in 2.3.1 which we could use to offset DateTimeOriginal, ModifyDate and other local datetime tags. GPSDateStamp/GPSTimeStamp are stored in UTC so can be used (theoretically) for deducing the original timezone

[dlemstra]

But that would mean that the values would need to have knowledge about eachother and that would be strange to me. The value now has no knowledge of the profile it is in.

[JimBobSquarePants]

Yeah, you're right. that would be strange. We should just parse via DateTimeStyles.AssumeLocal. Any calculation can be performed by the user.

[JimBobSquarePants]

Yo @GF-Huang did that answer your question?

[GF-Huang]

Sorry, I forget to read this issue..