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Merged
ptpt merged 1 commit into from
Sep 16, 2025
Merged

Write fully reduced Exif rationals with full precision #782

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90 changes: 61 additions & 29 deletions mapillary_tools/exif_write.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
import json
import logging
import math
from fractions import Fraction
from pathlib import Path

import piexif
Expand All @@ -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."""
Expand Down Expand Up @@ -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:
Expand Down
17 changes: 5 additions & 12 deletions tests/unit/test_exifedit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand All @@ -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)
Expand Down Expand Up @@ -118,13 +116,10 @@ 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
)
empty_exifedit.add_direction(test_direction, test_direction_ref)
empty_exifedit.write(EMPTY_EXIF_FILE_TEST)

exif_data = ExifRead(EMPTY_EXIF_FILE_TEST)
Expand Down Expand Up @@ -181,11 +176,10 @@ 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)
Expand All @@ -205,11 +199,10 @@ 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)
Expand Down
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