mediagoblin/tools/exif.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 from mediagoblin.tools.extlib.EXIF import process_file, Ratio
  18 from mediagoblin.processing import BadMediaFail
  19 from mediagoblin.tools.translate import pass_to_ugettext as _
  20
  21 # A list of tags that should be stored for faster access
  22 USEFUL_TAGS = [
  23     'Image Make',
  24     'Image Model',
  25     'EXIF FNumber',
  26     'EXIF Flash',
  27     'EXIF FocalLength',
  28     'EXIF ExposureTime',
  29     'EXIF ApertureValue',
  30     'EXIF ExposureMode',
  31     'EXIF ISOSpeedRatings',
  32     'EXIF UserComment',
  33     ]
  34
  35 def exif_fix_image_orientation(im, exif_tags):
  36     """
  37     Translate any EXIF orientation to raw orientation
  38
  39     Cons:
  40     - REDUCES IMAGE QUALITY by recompressig it
  41
  42     Pros:
  43     - Cures my neck pain
  44     """
  45     # Rotate image
  46     if 'Image Orientation' in exif_tags:
  47         rotation_map = {
  48             3: 180,
  49             6: 270,
  50             8: 90}
  51         orientation = exif_tags['Image Orientation'].values[0]
  52         if orientation in rotation_map.keys():
  53             im = im.rotate(
  54                 rotation_map[orientation])
  55
  56     return im
  57
  58 def extract_exif(filename):
  59     """
  60     Returns EXIF tags found in file at ``filename``
  61     """
  62     exif_tags = {}
  63
  64     try:
  65         image = open(filename)
  66         exif_tags = process_file(image)
  67     except IOError:
  68         raise BadMediaFail(_('Could not read the image file.'))
  69
  70     return exif_tags
  71
  72 def clean_exif(exif):
  73     '''
  74     Clean the result from anything the database cannot handle
  75     '''
  76     # Discard any JPEG thumbnail, for database compatibility
  77     # and that I cannot see a case when we would use it.
  78     # It takes up some space too.
  79     disabled_tags = [
  80         'Thumbnail JPEGInterchangeFormatLength',
  81         'JPEGThumbnail',
  82         'Thumbnail JPEGInterchangeFormat']
  83
  84     clean_exif = {}
  85
  86     for key, value in exif.items():
  87         if not key in disabled_tags:
  88             clean_exif[key] = _ifd_tag_to_dict(value)
  89
  90     return clean_exif
  91
  92 def _ifd_tag_to_dict(tag):
  93     data = {
  94         'printable': tag.printable,
  95         'tag': tag.tag,
  96         'field_type': tag.field_type,
  97         'field_offset': tag.field_offset,
  98         'field_length': tag.field_length,
  99         'values': None}
 100     if type(tag.values) == list:
 101         data['values'] = []
 102         for val in tag.values:
 103             if isinstance(val, Ratio):
 104                 data['values'].append(
 105                     _ratio_to_list(val))
 106             else:
 107                 data['values'].append(val)
 108     else:
 109         data['values'] = tag.values
 110
 111     return data
 112
 113 def _ratio_to_list(ratio):
 114     return [ratio.num, ratio.den]
 115
 116 def get_useful(tags):
 117     useful = {}
 118     for key, tag in tags.items():
 119         if key in USEFUL_TAGS:
 120             useful[key] = tag
 121
 122     return useful
 123
 124
 125 def get_gps_data(tags):
 126     """
 127     Processes EXIF data returned by EXIF.py
 128     """
 129     gps_data = {}
 130
 131     if not 'Image GPSInfo' in tags:
 132         return gps_data
 133
 134     try:
 135         dms_data = {
 136             'latitude': tags['GPS GPSLatitude'],
 137             'longitude': tags['GPS GPSLongitude']}
 138
 139         for key, dat in dms_data.items():
 140             gps_data[key] = (
 141                 lambda v:
 142                     float(v[0].num) / float(v[0].den) \
 143                     + (float(v[1].num) / float(v[1].den) / 60 )\
 144                     + (float(v[2].num) / float(v[2].den) / (60 * 60))
 145                 )(dat.values)
 146     except KeyError:
 147         pass
 148
 149     try:
 150         gps_data['direction'] = (
 151             lambda d:
 152                 float(d.num) / float(d.den)
 153             )(tags['GPS GPSImgDirection'].values[0])
 154     except KeyError:
 155         pass
 156
 157     try:
 158         gps_data['altitude'] = (
 159             lambda a:
 160                 float(a.num) / float(a.den)
 161             )(tags['GPS GPSAltitude'].values[0])
 162     except KeyError:
 163         pass
 164
 165     return gps_data