c# - 使用 WriteImageToSavedPhotosAlbum 时未保存 Gps exif 数据

Question

基本上我使用的示例代码来自 http://docs.xamarin.com/ios/recipes/Media/Video_and_Photos/Save_Photo_to_Album_with_Metadata

当我拍照并检查文件的 exif 数据时(通过 http://exifdata.com/ 或设备上的 Exif-Wizard)，我注意到 exif 数据不包含 GPS 信息，所以我手动收集位置信息、格式它，并将其添加到字典中，并将其包含在元字典中，如下所示。

btnCamera.Clicked += delegate {
TweetStation.Camera.TakePicture (this, (obj) => {
var photo = obj.ValueForKey (new NSString ("UIImagePickerControllerOriginalImage")) as    UIImage;
var meta = obj.ValueForKey (new NSString ("UIImagePickerControllerMediaMetadata")) as NSMutableDictionary;

var gpsDict = new NSMutableDictionary ();

...

gpsDict.SetValueForKey (NSObject.FromObject (GpsLong), new NSString ("GPSLongitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLongRef), new NSString ("GPSLongitudeRef"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLat), new NSString ("GPSLatitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLatRef), new NSString ("GPSLatitudeRef"));
gpsDict.SetValueForKey (NSObject.FromObject (DateTime.UtcNow.ToString ("HH:MM:ss.ff")),    new NSString ("GPSTimeStamp"));

meta.SetValueForKey (gpsDict, new NSString ("{GPS}"));

Console.WriteLine (meta.Description);

ALAssetsLibrary library = new ALAssetsLibrary ();
library.WriteImageToSavedPhotosAlbum (photo.CGImage, meta, (assetUrl, error) => {

if (error != null) {
Console.WriteLine ("error: "+ error.ToString ());
}
):

问题是，这似乎不起作用，if (error != null) {Console.WriteLine (error.ToString ());} 没有打印任何问题，并且在Console.WriteLine(meta.Description);输出如下

{
    DPIHeight = 72;
    DPIWidth = 72;
    Orientation = 6;
    "{Exif}" =     {
        ApertureValue = "2.970853654340484";
        BrightnessValue = "1.87496238139573";
        ColorSpace = 1;
        DateTimeDigitized = "2012:08:02 17:12:42";
        DateTimeOriginal = "2012:08:02 17:12:42";
        ExposureMode = 0;
        ExposureProgram = 2;
        ExposureTime = "0.06666666666666667";
        FNumber = "2.8";
        Flash = 24;
        FocalLength = "3.85";
        ISOSpeedRatings =         (
            160
        );
        MeteringMode = 5;
        PixelXDimension = 2592;
        PixelYDimension = 1936;
        SceneType = 1;
        SensingMethod = 2;
        Sharpness = 2;
        ShutterSpeedValue = "3.911199862602335";
        SubjectArea =         (
            1295,
            967,
            699,
            696
        );
        WhiteBalance = 0;
    };
    "{GPS}" =     {
        GPSLatitude = "30.35974270979283";
        GPSLatitudeRef = N;
        GPSLongitude = "91.13930279830274";
        GPSLongitudeRef = W;
        GPSTimeStamp = "22:08:44.66";
    };
    "{TIFF}" =     {
        DateTime = "2012:08:02 17:12:42";
        Make = Apple;
        Model = "iPhone 4";
        Software = "5.0.1";
        XResolution = 72;
        YResolution = 72;
    };
}

显示 GPS 数据。

所以，我很好奇我做错了什么，我对 monotouch(也是 mac)很陌生，所以请原谅一般的 WTF'ery。

Answer 1

问题解决:

似乎问题是我的 Exif Gps 数据 block 不正确，我使用了错误的名称，并且 block 不完整，正在更改

gpsDict.SetValueForKey (NSObject.FromObject (GpsLong), new NSString ("GPSLongitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLongRef), new NSString ("GPSLongitudeRef"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLat), new NSString ("GPSLatitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLatRef), new NSString ("GPSLatitudeRef"));
gpsDict.SetValueForKey (NSObject.FromObject (DateTime.UtcNow.ToString ("HH:MM:ss.ff")),    new NSString ("GPSTimeStamp"));

到

gpsDict.SetValueForKey(NSObject.FromObject(GpsAltitude),new NSString("Altitude"));
gpsDict.SetValueForKey(NSObject.FromObject(GpsAltitudeRef),new NSString("AltitudeRef"));

gpsDict.SetValueForKey(NSObject.FromObject(GpsImgDirection),new NSString("ImgDirection"));
gpsDict.SetValueForKey(NSObject.FromObject(GpsImgDirectionRef),new NSString("ImgDirectionRef"));

gpsDict.SetValueForKey (NSObject.FromObject (GpsLong), new NSString ("Longitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLongRef), new NSString ("LongitudeRef"));

gpsDict.SetValueForKey (NSObject.FromObject (GpsLat), new NSString ("Latitude"));
gpsDict.SetValueForKey (NSObject.FromObject (GpsLatRef), new NSString ("LatitudeRef"));

gpsDict.SetValueForKey (NSObject.FromObject (DateTime.UtcNow.ToString ("HH:MM:ss.ff")), new NSString ("TimeStamp"));

主要的变化是从所有标签名称中删除了 GPS 前缀，并添加了高度标签。

GPS exif block 应该如下所示

"{GPS}" =     {
    Altitude = "14.9281";
    AltitudeRef = 0;
    ImgDirection = "107.4554";
    ImgDirectionRef = T;
    Latitude = "30.35514548114219";
    LatitudeRef = N;
    Longitude = "91.13394105024713";
    LongitudeRef = W;
    TimeStamp = "15:08:57.93";
};