Extracting EXIF from JPEG

Question

I am getting hung up on reading EXIF data from my JPEGs. I thought it would be easy to do.

Thus far I have completed the following steps for my family's online image gallery (using C#/ASP.Net 3.5):

Upload a ZIP file containing JPEG's (that are from my iPhone 4)
Rename the JPEG's in the ZIP file using a preferred naming convention
Extract the JPEG's from the ZIP file to an images folder
Resize the images for various uses (such as thumbnails, etc.)
Save the filename and a selected category ID to SQL Server so that I can associate the two for display purposes

I would like to extract the latitude and longitude from the original JPEG image and then insert those values into my database in the same proc that inserts the filename and category ID (step # 5). I need these values to work with the Google Maps API. What is the simplest way to do it?

Update:

ExifLib looks great, but when I do the following:

double d; 
ExifReader er = new ExifReader(sFileName); 
er.GetTagValue<double>(ExifTags.GPSLatitude, out d);

I get this error on the last line:

Specified cast is not valid.

Any suggestions?

What are those Double[] value contain? You could try took ExifTags.GPSLatitude.First(), ExifTags.GPSLatitude.Average(), or you probably need to compose your own lambda expression if they're something else — Martheen, Jan 24 '11 at 04:42
The Double[] value contains the degrees, minutes and seconds. The following library handles it better, but EXIF metadata is a pain to work with! http://www.codeproject.com/KB/graphics/exiftagcol.aspx — Yoav, Jan 26 '11 at 02:39
So you want the latitude as plain double? Simply use ExifTags.GPSLatitude.Select(x=>x[0]+x[1]/60+x[2]/3600) — Martheen, Jan 26 '11 at 15:50

score 9 · Answer 1 · answered Jan 06 '12 at 09:02

To bring all the answers together, here is the completed solution.

using (ExifReader reader = new ExifReader(e.Target))
{
    Double[] GpsLongArray;
    Double[] GpsLatArray;
    Double GpsLongDouble;
    Double GpsLatDouble;

    if (reader.GetTagValue<Double[]>(ExifTags.GPSLongitude, out GpsLongArray) 
        && reader.GetTagValue<Double[]>(ExifTags.GPSLatitude, out GpsLatArray))
    {
        GpsLongDouble = GpsLongArray[0] + GpsLongArray[1] / 60 + GpsLongArray[2] / 3600;
        GpsLatDouble  = GpsLatArray[0]  + GpsLatArray[1]  / 60 + GpsLatArray[2]  / 3600;

        Console.WriteLine("The picture was taken at {0},{1}", GpsLongDouble, GpsLatDouble);

    }

}

Output:

    The picture was taken at 76.8593333333333,39.077

You must take ExifTags.GPSLongitudeRef, ExifTags.GPSLatitudeRef into account, otherwise you'll find yourself in China instead of California. — tsul, Feb 04 '17 at 07:59

score 2 · Answer 2 · answered Aug 12 '15 at 11:41

Another option for retrieving GPS metadata from images is to use the MetadataExtractor library. It's available on NuGet. It supports Exif GPS data from JPEG files, along with a tonne of other metadata types and file types.

To access the GPS location, use the following code:

var directories = ImageMetadataReader.ReadMetadata(jpegFilePath);

var gps = directories.OfType<GpsDirectory>().FirstOrDefault();

if (gps != null)
{
    var location = gps.GetGeoLocation();

    if (location != null)
        Console.WriteLine("Lat {0} Lng {1}", location.Latitude, location.Longitude);
}

Here's example output from an iPhone 6.

Extracting EXIF from JPEG

2 Answers2