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Image Metadata

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This article shows how to read and write image metadata properties and how to geotag files using the GeotagHelper utility class.

Image properties

The StorageFile.Properties property returns a StorageItemContentProperties object that provides access to content-related information about the file. Get the image-specific properties by calling GetImagePropertiesAsync. The returned ImageProperties object exposes members that contain basic image metadata fields, like the title of the image and the capture date.

private async void GetImageProperties(StorageFile imageFile)
{
    ImageProperties props = await imageFile.Properties.GetImagePropertiesAsync();

    string title = props.Title;
    if (title == null)
    {
        // Format does not support, or image does not contain Title property
    }

    DateTimeOffset date = props.DateTaken;
    if (date == null)
    {
        // Format does not support, or image does not contain DateTaken property
    }
}

To access a larger set of file metadata, use the Windows Property System, a set of file metadata properties that can be retrieved with a unique string identifier. Create a list of strings and add the identifier for each property you want to retrieve. The ImageProperties.RetrievePropertiesAsync method takes this list of strings and returns a dictionary of key/value pairs where the key is the property identifier and the value is the property value.

ImageProperties props = await imageFile.Properties.GetImagePropertiesAsync();

var requests = new System.Collections.Generic.List<string>();
requests.Add("System.Photo.Orientation");
requests.Add("System.Photo.Aperture");

IDictionary<string, object> retrievedProps = await props.RetrievePropertiesAsync(requests);

ushort orientation;
if (retrievedProps.ContainsKey("System.Photo.Orientation"))
{
    orientation = (ushort)retrievedProps["System.Photo.Orientation"];
}

double aperture;
if (retrievedProps.ContainsKey("System.Photo.Aperture"))
{
    aperture = (double)retrievedProps["System.Photo.Aperture"];
}

  • For a complete list of Windows Properties, including the identifiers and type for each property, see Windows Properties.

  • Some properties are only supported for certain file containers and image codecs. For a listing of the image metadata supported for each image type, see Photo Metadata Policies.

  • Because properties that are unsupported may return a null value when retrieved, always check for null before using a returned metadata value.

Geotag helper

GeotagHelper is a utility class that makes it easy to tag images with geographic data using the Windows.Devices.Geolocation APIs directly, without having to manually parse or construct the metadata format.

If you already have a Geopoint object representing the location you want to tag in the image, either from a previous use of the geolocation APIs or some other source, you can set the geotag data by calling GeotagHelper.SetGeotagAsync and passing in a StorageFile and the Geopoint.

var point = new Geopoint(
new BasicGeoposition
{
    Latitude = 48.8567,
    Longitude = 2.3508,
});

await GeotagHelper.SetGeotagAsync(imageFile, point);

To set the geotag data using the device's current location, create a new Geolocator object and call GeotagHelper.SetGeotagFromGeolocatorAsync passing in the Geolocator and the file to be tagged.

var locator = new Geolocator();

// Shows the user consent UI if needed
var accessStatus = await Geolocator.RequestAccessAsync();
if (accessStatus == GeolocationAccessStatus.Allowed)
{
    await GeotagHelper.SetGeotagFromGeolocatorAsync(imageFile, locator);
}

To get a GeoPoint representing the geotagged location of an image file, call GetGeotagAsync.

Geopoint geoPoint = await GeotagHelper.GetGeotagAsync(imageFile);

Decode and encode image metadata

The most advanced way of working with image data is to read and write the properties on the stream level using a BitmapDecoder or a BitmapEncoder. For these operations you can use Windows Properties to specify the data you are reading or writing, but you can also use the metadata query language provided by the Windows Imaging Component (WIC) to specify the path to a requested property.

Reading image metadata using this technique requires you to have a BitmapDecoder that was created with the source image file stream. For information on how to do this, see Imaging.

Once you have the decoder, create a list of strings and add a new entry for each metadata property you want to retrieve, using either the Windows Property identifier string or a WIC metadata query. Call the BitmapPropertiesView.GetPropertiesAsync method on the decoder's BitmapProperties member to request the specified properties. The properties are returned in a dictionary of key/value pairs containing the property name or path and the property value.

private async void ReadImageMetadata(BitmapDecoder bitmapDecoder)
{

    var requests = new System.Collections.Generic.List<string>();
    requests.Add("System.Photo.Orientation"); // Windows property key for EXIF orientation
    requests.Add("/xmp/dc:creator"); // WIC metadata query for Dublin Core creator

    try
    {
        var retrievedProps = await bitmapDecoder.BitmapProperties.GetPropertiesAsync(requests);

        ushort orientation;
        if (retrievedProps.ContainsKey("System.Photo.Orientation"))
        {
            orientation = (ushort)retrievedProps["System.Photo.Orientation"].Value;
        }

        string creator;
        if (retrievedProps.ContainsKey("/xmp/dc:creator"))
        {
            creator = (string)retrievedProps["/xmp/dc:creator"].Value;
        }
    }
    catch (Exception err)
    {
        switch (err.HResult)
        {
            case unchecked((int)0x88982F41): // WINCODEC_ERR_PROPERTYNOTSUPPORTED
                                             // The file format does not support the requested metadata.
                break;
            case unchecked((int)0x88982F81): // WINCODEC_ERR_UNSUPPORTEDOPERATION
                                             // The file format does not support any metadata.
            default:
                throw err;
        }
    }
}

  • For information on the WIC metadata query language and the properties supported, see WIC image format native metadata queries.

  • Many metadata properties are only supported by a subset of image types. GetPropertiesAsync will fail with the error code 0x88982F41 if one of the requested properties is not supported by the image associated with the decoder and 0x88982F81 if the image does not support metadata at all. The constants associated with these error codes are WINCODEC_ERR_PROPERTYNOTSUPPORTED and WINCODEC_ERR_UNSUPPORTEDOPERATION and are defined in the winerror.h header file.

  • Because an image may or may not contain a value for a particular property, use the IDictionary.ContainsKey to verify that a property is present in the results before attempting to access it.

Writing image metadata to the stream requires a BitmapEncoder associated with the image output file.

Create a BitmapPropertySet object to contain the property values you want set. Create a BitmapTypedValue object to represent the property value. This object uses an object as the value and member of the PropertyType enumeration that defines the type of the value. Add the BitmapTypedValue to the BitmapPropertySet and then call BitmapProperties.SetPropertiesAsync to cause the encoder to write the properties to the stream.

private async void WriteImageMetadata(BitmapEncoder bitmapEncoder)
{
    var propertySet = new Windows.Graphics.Imaging.BitmapPropertySet();
    var orientationValue = new Windows.Graphics.Imaging.BitmapTypedValue(
        1, // Defined as EXIF orientation = "normal"
        Windows.Foundation.PropertyType.UInt16
        );

    propertySet.Add("System.Photo.Orientation", orientationValue);

    try
    {
        await bitmapEncoder.BitmapProperties.SetPropertiesAsync(propertySet);
    }
    catch (Exception err)
    {
        switch (err.HResult)
        {
            case unchecked((int)0x88982F41): // WINCODEC_ERR_PROPERTYNOTSUPPORTED
                                             // The file format does not support this property.
                break;
            default:
                throw err;
        }
    }
}