💭 How to access GPS location tags in photo metadata?

iamnotreddy commented 3 months ago

Question

I'm trying to access the GPS metadata from the photo metadata property but am unable to locate it. My understanding is that it should appear in the metadata object in a property called '{GPS}'.

I went into the native code and I was able to log the expected GPS metadata, so I'm unsure if this is an actual issue or just something I'm doing wrong so I'll post my findings. Curious if anyone else has run into these issues with accessing GPS metadata and / or figured a way to resolve it.

When I log the metadata property from the photo inside react native:

const photo = await camera.current?.takePhoto();
const metadata = photo?.metadata;
console.log('Raw Metadata:', JSON.stringify(metadata));

I don't see the GPS metadata tag (removed some fields for brevity):

Raw Metadata: {
  "DPIWidth": 72,
  "{TIFF}": {
    "ResolutionUnit": 2,
    "Software": "17.4.1",
    "Make": "Apple",
    "DateTime": "2024:05:24 10:25:21",
    "XResolution": 72,
    "HostComputer": "iPhone 13",
    "Model": "iPhone 13",
    "YResolution": 72
  },
  "kCGImageDestinationICCProfile": null,
  "{MakerApple}": {
   ...
  },
  "DPIHeight": 72,
  "Orientation": 6,
  "{Exif}": {
    "DateTimeOriginal": "2024:05:24 10:25:21",
    "ExposureTime": 0.0017699115044247787,
    "FNumber": 1.6,
    ...
  }
}

I went into the native code and I was able to log the GPS data inside the MetadataProvider file. This is what itsreplacementMetadata function returns (also abridged some fields):

["DPIHeight": 72, 
"kCGImageDestinationICCProfile": ..., 
"{MakerApple}": {
    1 = 14;
    ...
}, 
"DPIWidth": 72, 
"{Exif}": 
["WhiteBalance": 0, "UserComment": "Captured with VisionCamera by mrousavy", 
....
"DateTimeDigitized": 2024:05:24 10:25:21], 
"Orientation": 6, 
"{TIFF}": {
    DateTime = "2024:05:24 10:25:21";
    HostComputer = "iPhone 13";
    ...
}, 
"{GPS}": {
    Altitude = "10.41956996917725";
    AltitudeRef = 0;
    DOP = [redacted]
    DateStamp = "2024:05:24";
    ImgDirection = "188.7100982666016";
    ImgDirectionRef = T;
    Latitude = [redacted]
    LatitudeRef = N;
    Longitude = [redacted];
    LongitudeRef = W;
    TimeStamp = "10:25:21";
}]

The GPS data above appears to be correct and is what I would hope to see inside the photo metadata. This also makes me think it's not a location permissions issue on my end.

Something else I noticed in the native code: when I log photo.metadata inside the photoOutput function inside PhotoCaptureDelegate file, the GPS tag does NOT appear (but I see EXIF, TIFF etc.).

I don't have too much understanding of the native code and how it all ties together but hoping this information is helpful. Please let me know if any additional context is needed from my side.

What I tried

I've ensured the following:

enableLocation is set to true in the <Camera> component
added NSLocationWhenInUseUsageDescription to Info.plist
confirmed I'm correctly obtaining location permissions: hasPermission is true from the useLocationPermission hook

VisionCamera Version

4.0.5

Additional information

[ ] I am using Expo
[X] I have read the Troubleshooting Guide
[X] I agree to follow this project's Code of Conduct
[X] I searched for similar questions in the issues page as well as in the discussions page and found none.

mrousavy commented 3 months ago

Hm well maybe it just doesn't have the replacement data at this point yet. It's definitely in the file, so if you read it you will get GPS metadata.

Also on Android there's no way to get that metadata currently - which sucks. So this is not really a public API at all.

iamnotreddy commented 3 months ago

@mrousavy - appreciate you getting back to me!

just to clarify, are referring to reading the GPS metadata from this photo file? my original understanding was that I could read the GPS metadata from the photo metadata so that might make sense why I'm not seeing it

aesqe commented 3 months ago

@iamnotreddy I also don't see the GPS data if I console.log the camera.takePhoto output. However, @mrousavy is right and the data is contained in the file metadata. https://github.com/francisco-sanchez-molina/react-native-exif can read that data and the values are correct in my case, at least on the latest iOS using iPhone 13.

iamnotreddy commented 3 months ago

Thanks for confirming on the takePhoto output @aesqe! That makes sense, I will try to get the GPS tag from the file metadata

mrousavy / react-native-vision-camera