fix: Write fully reduced Exif rationals with full precision

Add debug (verbose) messages on written tags

Author: JakeSmarter

mapillary_tools/exif_write.py

@@ -6,6 +6,7 @@
 import json
 import logging
 import math
+from fractions import Fraction
 from pathlib import Path
 
 import piexif
@@ -29,16 +30,19 @@ def __init__(self, filename_or_bytes: Path | bytes) -> None:
 
     @staticmethod
     def decimal_to_dms(
-        value: float, precision: int
-    ) -> tuple[tuple[float, int], tuple[float, int], tuple[float, int]]:
-        """
-        Convert decimal position to degrees, minutes, seconds in a fromat supported by EXIF
-        """
-        deg = math.floor(value)
-        min = math.floor((value - deg) * 60)
-        sec = math.floor((value - deg - min / 60) * 3600 * precision)
-
-        return (deg, 1), (min, 1), (sec, precision)
+        value: float,
+    ) -> tuple[tuple[int, int], tuple[int, int], tuple[int, int]]:
+        """Convert decimal position to Exif degrees, minutes, and seconds rationals"""
+
+        deg: int = int(value)
+        min: int = int(value := (value - deg) * 60)
+        sec: float = (value - min) * 60
+
+        return (
+            (deg, 1),
+            (min, 1),
+            (Fraction.from_float(sec).limit_denominator().as_integer_ratio()),
+        )
 
     def add_image_description(self, data: dict) -> None:
         """Add a dict to image description."""
@@ -83,41 +87,69 @@ def add_gps_datetime(self, dt: datetime.datetime) -> None:
         self._ef["GPS"][piexif.GPSIFD.GPSTimeStamp] = (
             (dt.hour, 1),
             (dt.minute, 1),
-            # num / den = (dt.second * 1e6 + dt.microsecond) / 1e6
-            (int(dt.second * 1e6 + dt.microsecond), int(1e6)),
+            (
+                Fraction.from_float(dt.second + dt.microsecond / 1e6)
+                .limit_denominator()
+                .as_integer_ratio()
+            ),
         )
-
-    def add_lat_lon(self, lat: float, lon: float, precision: float = 1e7) -> None:
+        if LOG.isEnabledFor(logging.DEBUG):
+            LOG.debug(
+                'GPSDateStamp: "%s"\tGPSTimeStamp: %s',
+                self._ef["GPS"][piexif.GPSIFD.GPSDateStamp],
+                self._ef["GPS"][piexif.GPSIFD.GPSTimeStamp],
+            )
+
+    def add_lat_lon(self, lat: float, lon: float) -> None:
         """Add lat, lon to gps (lat, lon in float)."""
+
         self._ef["GPS"][piexif.GPSIFD.GPSLatitudeRef] = "N" if lat > 0 else "S"
+        self._ef["GPS"][piexif.GPSIFD.GPSLatitude] = ExifEdit.decimal_to_dms(
+            math.fabs(lat)
+        )
         self._ef["GPS"][piexif.GPSIFD.GPSLongitudeRef] = "E" if lon > 0 else "W"
         self._ef["GPS"][piexif.GPSIFD.GPSLongitude] = ExifEdit.decimal_to_dms(
-            abs(lon), int(precision)
-        )
-        self._ef["GPS"][piexif.GPSIFD.GPSLatitude] = ExifEdit.decimal_to_dms(
-            abs(lat), int(precision)
+            math.fabs(lon)
         )
+        if LOG.isEnabledFor(logging.DEBUG):
+            LOG.debug(
+                "GPSLatitude: %s\tGPSLongitude: %s",
+                self._ef["GPS"][piexif.GPSIFD.GPSLatitude],
+                self._ef["GPS"][piexif.GPSIFD.GPSLongitude],
+            )
+
+    def add_altitude(self, altitude: float) -> None:
+        """Add altitude."""
 
-    def add_altitude(self, altitude: float, precision: int = 100) -> None:
-        """Add altitude (pre is the precision)."""
         ref = 0 if altitude > 0 else 1
         self._ef["GPS"][piexif.GPSIFD.GPSAltitude] = (
-            int(abs(altitude) * precision),
-            precision,
+            Fraction.from_float(math.fabs(altitude))
+            .limit_denominator()
+            .as_integer_ratio()
         )
         self._ef["GPS"][piexif.GPSIFD.GPSAltitudeRef] = ref
-
-    def add_direction(
-        self, direction: float, ref: str = "T", precision: int = 100
-    ) -> None:
+        if LOG.isEnabledFor(logging.DEBUG):
+            LOG.debug(
+                'GPSAltitudeRef: "%s"\tGPSAltitude: %s',
+                self._ef["GPS"][piexif.GPSIFD.GPSAltitudeRef],
+                self._ef["GPS"][piexif.GPSIFD.GPSAltitude],
+            )
+
+    def add_direction(self, direction: float, ref: str = "T") -> None:
         """Add image direction."""
+
         # normalize direction
-        direction = direction % 360.0
+        direction = math.fmod(direction, 360.0)
         self._ef["GPS"][piexif.GPSIFD.GPSImgDirection] = (
-            int(abs(direction) * precision),
-            precision,
+            Fraction.from_float(direction).limit_denominator().as_integer_ratio()
         )
         self._ef["GPS"][piexif.GPSIFD.GPSImgDirectionRef] = ref
+        if LOG.isEnabledFor(logging.DEBUG):
+            LOG.debug(
+                'GPSImgDirectionRef: "%s"\tGPSImgDirection: %s',
+                self._ef["GPS"][piexif.GPSIFD.GPSImgDirectionRef],
+                self._ef["GPS"][piexif.GPSIFD.GPSImgDirection],
+            )
 
     def add_make(self, make: str) -> None:
         if not make:

tests/unit/test_exifedit.py

@@ -68,11 +68,10 @@ def add_date_time_original_general(test_obj, filename: Path):
 def add_lat_lon_general(test_obj, filename):
     test_latitude = 50.5475894785
     test_longitude = 15.595866685
-    precision = 1e7
 
     empty_exifedit = ExifEdit(filename)
 
-    empty_exifedit.add_lat_lon(test_latitude, test_longitude, precision)
+    empty_exifedit.add_lat_lon(test_latitude, test_longitude)
     empty_exifedit.write(EMPTY_EXIF_FILE_TEST)
 
     exif_data = ExifRead(EMPTY_EXIF_FILE_TEST)
@@ -82,11 +81,10 @@ def add_lat_lon_general(test_obj, filename):
 
 def add_altitude_general(test_obj, filename: Path):
     test_altitude = 15.5
-    test_altitude_precision = 100
 
     empty_exifedit = ExifEdit(filename)
 
-    empty_exifedit.add_altitude(test_altitude, test_altitude_precision)
+    empty_exifedit.add_altitude(test_altitude)
     empty_exifedit.write(EMPTY_EXIF_FILE_TEST)
 
     exif_data = ExifRead(EMPTY_EXIF_FILE_TEST)
@@ -118,12 +116,11 @@ def add_repeatedly_time_original_general(test_obj, filename):
 def add_direction_general(test_obj, filename):
     test_direction = 1
     test_direction_ref = "T"
-    test_direction_precision = 100
 
     empty_exifedit = ExifEdit(filename)
 
     empty_exifedit.add_direction(
-        test_direction, test_direction_ref, test_direction_precision
+        test_direction, test_direction_ref
     )
     empty_exifedit.write(EMPTY_EXIF_FILE_TEST)
 
@@ -181,11 +178,10 @@ def test_add_repeatedly_time_original(self):
 
     def test_add_time_original_to_existing_exif(self):
         test_altitude = 15.5
-        test_altitude_precision = 100
 
         empty_exifedit = ExifEdit(EMPTY_EXIF_FILE_TEST)
 
-        empty_exifedit.add_altitude(test_altitude, test_altitude_precision)
+        empty_exifedit.add_altitude(test_altitude)
         empty_exifedit.write(EMPTY_EXIF_FILE_TEST)
 
         test_datetime = datetime.datetime(2016, 9, 30, 8, 29, 26, 249000)
@@ -205,11 +201,10 @@ def test_add_time_original_to_existing_exif(self):
     def test_add_negative_lat_lon(self):
         test_latitude = -50.5
         test_longitude = -15.5
-        precision = 1e7
 
         empty_exifedit = ExifEdit(EMPTY_EXIF_FILE_TEST)
 
-        empty_exifedit.add_lat_lon(test_latitude, test_longitude, precision)
+        empty_exifedit.add_lat_lon(test_latitude, test_longitude)
         empty_exifedit.write(EMPTY_EXIF_FILE_TEST)
 
         exif_data = ExifRead(EMPTY_EXIF_FILE_TEST)