Added write_exif function, calculates location in degree / minutes.

Assembles metadata info and writes them to the target_image.

functions.py

@@ -6,8 +6,8 @@
 from datetime import datetime
 import os
 import shutil
+from fractions import Fraction
 import pyexiv2
-import fractions
 
 class Radiation:
     ''' Handles CSV processing. '''
@@ -66,7 +66,17 @@ class Photo:
         return pic_aware_time
 
 class Exif:
-    ''' Converts, compiles and writes Exif-Tags from given values. '''
+    ''' Converts, compiles and writes Exif-Tags from given values. 
+    
+    Arguments:
+    photo: file name of photo to modify
+    radiation: radiation levels in µS/h
+    latitude: latitude as float
+    longitude: longitude as float
+    elevation: elevation as float
+    dry_run: whether to acutally write (True / False)
+    '''
+
     def __init__(self, photo, radiation, latitude, longitude, elevation, dry_run):
         # self.get_degree = self._to_degree(value, loc)
         self.write_exif = self._write_exif(photo, radiation, latitude, longitude, elevation, dry_run)
@@ -93,27 +103,39 @@ class Exif:
         metadata = pyexiv2.ImageMetadata(photo)
         metadata.read()
 
-        lat_deg = self._to_degree(latitude, ["S", "N"])
-        lng_deg = self._to_degree(longitude, ["W", "E"])
+        latitude_degree = self._to_degree(latitude, ["S", "N"])
+        longitude_degree = self._to_degree(longitude, ["W", "E"])
 
-        print(lat_deg)
-        print(lng_deg)
+        print(latitude_degree)
+        print(longitude_degree)
+        
+        # convert decimal coordinates into fractions required for pyexiv2
+        exiv2_latitude = (Fraction(latitude_degree[0] * 60 + latitude_degree[1], 60),
+                          Fraction(int(round(latitude_degree[2] * 100, 0)), 6000),
+                          Fraction(0, 1))
+        exiv2_longitude = (Fraction(longitude_degree[0] * 60 + longitude_degree[1], 60),
+                           Fraction(int(round(longitude_degree[2] * 100, 0)), 6000),
+                           Fraction(0, 1))
 
         # Set new UserComment
         new_comment = 'Radiation ☢ ' + str(radiation) + ' µS/h'
-        # Exif tags to write
-        keys = ['Exif.Photo.UserComment', 'Exif.Photo.latitude', 'Exif.Photo.longitude']
-        # Values to write
-        values = [new_comment, latitude, longitude]
         
-        # Create metadata object with all data to write
-        #for key, value in zip(keys, values):
-            # Only create object if there is anything to fill with
-        #    if value is not None:
-        #        metadata[key] = pyexiv2.ExifTag(key, value)
+        # Exif tags to write
+        metadata['Exif.GPSInfo.GPSLatitude'] = exiv2_latitude
+        metadata['Exif.GPSInfo.GPSLatitudeRef'] = latitude_degree[3]
+        metadata['Exif.GPSInfo.GPSLongitude'] = exiv2_longitude
+        metadata['Exif.GPSInfo.GPSLongitudeRef'] = longitude_degree[3]
+        metadata['Exif.GPSInfo.GPSAltitude'] = Fraction(elevation)
+        metadata['Exif.GPSInfo.GPSAltitudeRef'] = '0'
+        metadata['Exif.Image.GPSTag'] = 654
+        metadata['Exif.GPSInfo.GPSMapDatum'] = "WGS-84"
+        metadata['Exif.GPSInfo.GPSVersionID'] = '2 0 0 0'
+        metadata['Exif.Photo.UserComment'] = new_comment
+
+        print(new_comment)
 
         # Write Exif tags to file, if not in dry-run mode
-        #if dry_run is not True:
-        #    metadata.write()
+        if dry_run is not True:
+            metadata.write()
 
         return new_comment