Stringify GPS directions (N/W/S/E) as unquoted.

src/tag.rs

@@ -28,7 +28,7 @@ use std::fmt;
 
 use value;
 use value::Value;
-use util::atou16;
+use util::{atou16, isupper};
 
 /// A tag of a TIFF field.
 //
@@ -434,11 +434,11 @@ generate_well_known_tag_constants!(
     // Depends on the Exif version.
     (GPSVersionID, 0x0, DefaultValue::ContextDependent, d_gpsver,
      "GPS tag version"),
-    (GPSLatitudeRef, 0x1, DefaultValue::None, d_default,
+    (GPSLatitudeRef, 0x1, DefaultValue::None, d_gpslatlongref,
      "North or south latitude"),
     (GPSLatitude, 0x2, DefaultValue::None, d_gpsdms,
      "Latitude"),
-    (GPSLongitudeRef, 0x3, DefaultValue::None, d_default,
+    (GPSLongitudeRef, 0x3, DefaultValue::None, d_gpslatlongref,
      "East or West Longitude"),
     (GPSLongitude, 0x4, DefaultValue::None, d_gpsdms,
      "Longitude"),
@@ -470,11 +470,11 @@ generate_well_known_tag_constants!(
      "Direction of image"),
     (GPSMapDatum, 0x12, DefaultValue::None, d_default,
      "Geodetic survey data used"),
-    (GPSDestLatitudeRef, 0x13, DefaultValue::None, d_default,
+    (GPSDestLatitudeRef, 0x13, DefaultValue::None, d_gpslatlongref,
      "Reference for latitude of destination"),
     (GPSDestLatitude, 0x14, DefaultValue::None, d_gpsdms,
      "Latitude of destination"),
-    (GPSDestLongitudeRef, 0x15, DefaultValue::None, d_default,
+    (GPSDestLongitudeRef, 0x15, DefaultValue::None, d_gpslatlongref,
      "Reference for longitude of destination"),
     (GPSDestLongitude, 0x16, DefaultValue::None, d_gpsdms,
      "Longitude of destination"),
@@ -1023,6 +1023,17 @@ fn d_gpsver(w: &mut fmt::Write, value: &Value) -> fmt::Result {
     }
 }
 
+// GPSLatitudeRef (Exif/GPS 0x1), GPSLongitudeRef (Exif/GPS 0x3)
+// GPSDestLatitudeRef (Exif/GPS 0x13), GPSDestLongitudeRef (Exif/GPS 0x15)
+fn d_gpslatlongref(w: &mut fmt::Write, value: &Value) -> fmt::Result {
+    match *value {
+        Value::Ascii(ref v) if (v.len() == 1 && v[0].len() == 1 &&
+                                isupper(v[0][0])) =>
+            w.write_char(v[0][0] as char),
+        _ => d_default(w, value),
+    }
+}
+
 // GPSLatitude (Exif/GPS 0x2), GPSLongitude (Exif 0x4),
 // GPSDestLatitude (Exif/GPS 0x14), GPSDestLongitude (Exif 0x16)
 fn d_gpsdms(w: &mut fmt::Write, value: &Value) -> fmt::Result {

src/util.rs

@@ -28,6 +28,9 @@ use std::io;
 
 use error::Error;
 
+const ASCII_A: u8 = 0x41;
+const ASCII_Z: u8 = 0x5a;
+
 pub fn read8<R>(reader: &mut R) -> Result<u8, io::Error> where R: io::Read {
     let mut buf: [u8; 1] = unsafe { ::std::mem::uninitialized() };
     reader.read_exact(&mut buf).and(Ok(buf[0]))
@@ -60,6 +63,10 @@ pub fn atou16(bytes: &[u8]) -> Result<u16, Error> {
     Ok(n)
 }
 
+pub fn isupper(c: u8) -> bool {
+    ASCII_A <= c && c <= ASCII_Z
+}
+
 #[cfg(test)]
 mod tests {
     use std::io::Cursor;
@@ -105,4 +112,13 @@ mod tests {
         assert_err_pat!(atou16(b":"), Error::InvalidFormat(_));
         assert_err_pat!(atou16(b"-1"), Error::InvalidFormat(_));
     }
+
+    #[test]
+    fn isupper() {
+        assert!(super::isupper(b'A'));
+        assert!(super::isupper(b'Z'));
+        assert!(!super::isupper(b'A' - 1));
+        assert!(!super::isupper(b'Z' + 1));
+        assert!(!super::isupper(b'a'));
+    }
 }