Loupe/src/image_metadata/gps.rs

#[derive(Debug, Clone, Copy)]
pub struct GPSLocation {
    pub latitude: GPSCoord,
    pub longitude: GPSCoord,
}

#[derive(Debug, Clone, Copy)]
pub struct GPSCoord {
    sing: bool,
    deg: f64,
    min: Option<f64>,
    sec: Option<f64>,
}

impl GPSCoord {
    fn to_f64(&self) -> f64 {
        let sign = if self.sing { 1. } else { -1. };

        let min = self.min.unwrap_or_default();
        let sec = self.sec.unwrap_or_default();

        sign * (self.deg + min / 60. + sec / 60. / 60.)
    }

    fn display(&self, reference: &str) -> String {
        let deg = self.deg;

        if let (Some(min), Some(sec)) = (self.min, self.sec) {
            format!("{deg}° {min}′ {sec}″ {reference}")
        } else if let Some(min) = self.min {
            format!("{deg}° {min}′ {reference}")
        } else {
            format!("{deg}° {reference}")
        }
    }

    fn latitude_sign(reference: &[Vec<u8>]) -> Option<bool> {
        let reference = reference.first().and_then(|x| x.first())?;
        match reference.to_ascii_uppercase() {
            b'N' => Some(true),
            b'S' => Some(false),
            _ => None,
        }
    }

    fn longitude_sign(reference: &[Vec<u8>]) -> Option<bool> {
        let reference = reference.first().and_then(|x| x.first())?;
        match reference.to_ascii_uppercase() {
            b'E' => Some(true),
            b'W' => Some(false),
            _ => None,
        }
    }

    fn position_exif(position: &[exif::Rational]) -> Option<(f64, Option<f64>, Option<f64>)> {
        Some((
            position.get(0).map(exif::Rational::to_f64)?,
            position.get(1).map(exif::Rational::to_f64),
            position.get(2).map(exif::Rational::to_f64),
        ))
    }
}

impl GPSLocation {
    pub fn for_exif(
        latitude: &[exif::Rational],
        latitude_ref: &[Vec<u8>],
        longitude: &[exif::Rational],
        longitude_ref: &[Vec<u8>],
    ) -> Option<Self> {
        let (lat_deg, lat_min, lat_sec) = GPSCoord::position_exif(latitude)?;
        let lat_sign = GPSCoord::latitude_sign(latitude_ref)?;

        let (lon_deg, lon_min, lon_sec) = GPSCoord::position_exif(longitude)?;
        let lon_sign = GPSCoord::longitude_sign(longitude_ref)?;

        Some(Self {
            latitude: GPSCoord {
                sing: lat_sign,
                deg: lat_deg,
                min: lat_min,
                sec: lat_sec,
            },
            longitude: GPSCoord {
                sing: lon_sign,
                deg: lon_deg,
                min: lon_min,
                sec: lon_sec,
            },
        })
    }

    pub fn display(&self) -> String {
        if let Some(world) = libgweather::Location::world() {
            let location = world.find_nearest_city(self.latitude.to_f64(), self.longitude.to_f64());
            if let (Some(city), Some(country)) = (location.city_name(), location.country_name()) {
                return format!("{city}, {country}");
            }
        }

        // fallback
        self.latitude_display() + "\n" + &self.longitude_display()
    }

    pub fn latitude_display(&self) -> String {
        let coord = self.latitude;
        let reference = if coord.sing { "N" } else { "S" };

        coord.display(reference)
    }

    pub fn longitude_display(&self) -> String {
        let coord = self.longitude;
        let reference = if coord.sing { "E" } else { "W" };

        coord.display(reference)
    }

    pub fn geo_uri(&self) -> String {
        let latitude = self.latitude.to_f64();
        let longitude = self.longitude.to_f64();
        // six decimal places gives as more than a meter accuracy
        format!("geo:{latitude:.6},{longitude:.6}")
    }
}