1 files changed, 187 insertions, 0 deletions
diff --git a/mediagoblin/tools/exif.py b/mediagoblin/tools/exif.py
new file mode 100644
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+++ b/mediagoblin/tools/exif.py
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+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+try:
+    from EXIF import process_file, Ratio
+except ImportError:
+    from mediagoblin.tools.extlib.EXIF import process_file, Ratio
+
+from mediagoblin.processing import BadMediaFail
+from mediagoblin.tools.translate import pass_to_ugettext as _
+
+# A list of tags that should be stored for faster access
+USEFUL_TAGS = [
+    'Image Make',
+    'Image Model',
+    'EXIF FNumber',
+    'EXIF Flash',
+    'EXIF FocalLength',
+    'EXIF ExposureTime',
+    'EXIF ApertureValue',
+    'EXIF ExposureMode',
+    'EXIF ISOSpeedRatings',
+    'EXIF UserComment',
+    ]
+
+
+def exif_image_needs_rotation(exif_tags):
+    """
+    Returns True if EXIF orientation requires rotation
+    """
+    return 'Image Orientation' in exif_tags \
+        and exif_tags['Image Orientation'].values[0] != 1
+
+
+def exif_fix_image_orientation(im, exif_tags):
+    """
+    Translate any EXIF orientation to raw orientation
+
+    Cons:
+    - Well, it changes the image, which means we'll recompress
+      it... not a problem if scaling it down already anyway.  We might
+      lose some quality in recompressing if it's at the same-size
+      though
+
+    Pros:
+    - Prevents neck pain
+    """
+    # Rotate image
+    if 'Image Orientation' in exif_tags:
+        rotation_map = {
+            3: 180,
+            6: 270,
+            8: 90}
+        orientation = exif_tags['Image Orientation'].values[0]
+        if orientation in rotation_map:
+            im = im.rotate(
+                rotation_map[orientation])
+
+    return im
+
+
+def extract_exif(filename):
+    """
+    Returns EXIF tags found in file at ``filename``
+    """
+    try:
+        with file(filename) as image:
+            return process_file(image, details=False)
+    except IOError:
+        raise BadMediaFail(_('Could not read the image file.'))
+
+
+def clean_exif(exif):
+    '''
+    Clean the result from anything the database cannot handle
+    '''
+    # Discard any JPEG thumbnail, for database compatibility
+    # and that I cannot see a case when we would use it.
+    # It takes up some space too.
+    disabled_tags = [
+        'Thumbnail JPEGInterchangeFormatLength',
+        'JPEGThumbnail',
+        'Thumbnail JPEGInterchangeFormat']
+
+    return dict((key, _ifd_tag_to_dict(value)) for (key, value)
+            in exif.iteritems() if key not in disabled_tags)
+
+
+def _ifd_tag_to_dict(tag):
+    '''
+    Takes an IFD tag object from the EXIF library and converts it to a dict
+    that can be stored as JSON in the database.
+    '''
+    data = {
+        'printable': tag.printable,
+        'tag': tag.tag,
+        'field_type': tag.field_type,
+        'field_offset': tag.field_offset,
+        'field_length': tag.field_length,
+        'values': None}
+
+    if isinstance(tag.printable, str):
+        # Force it to be decoded as UTF-8 so that it'll fit into the DB
+        data['printable'] = tag.printable.decode('utf8', 'replace')
+
+    if type(tag.values) == list:
+        data['values'] = [_ratio_to_list(val) if isinstance(val, Ratio) else val
+                for val in tag.values]
+    else:
+        if isinstance(tag.values, str):
+            # Force UTF-8, so that it fits into the DB
+            data['values'] = tag.values.decode('utf8', 'replace')
+        else:
+            data['values'] = tag.values
+
+    return data
+
+
+def _ratio_to_list(ratio):
+    return [ratio.num, ratio.den]
+
+
+def get_useful(tags):
+    return dict((key, tag) for (key, tag) in tags.iteritems())
+
+
+def get_gps_data(tags):
+    """
+    Processes EXIF data returned by EXIF.py
+    """
+    gps_data = {}
+
+    if not 'Image GPSInfo' in tags:
+        return gps_data
+
+    try:
+        dms_data = {
+            'latitude': tags['GPS GPSLatitude'],
+            'longitude': tags['GPS GPSLongitude']}
+
+        for key, dat in dms_data.iteritems():
+            gps_data[key] = (
+                lambda v:
+                    float(v[0].num) / float(v[0].den) \
+                    + (float(v[1].num) / float(v[1].den) / 60) \
+                    + (float(v[2].num) / float(v[2].den) / (60 * 60))
+                )(dat.values)
+
+        if tags['GPS GPSLatitudeRef'].values == 'S':
+            gps_data['latitude'] /= -1
+
+        if tags['GPS GPSLongitudeRef'].values == 'W':
+            gps_data['longitude'] /= -1
+
+    except KeyError:
+        pass
+
+    try:
+        gps_data['direction'] = (
+            lambda d:
+                float(d.num) / float(d.den)
+            )(tags['GPS GPSImgDirection'].values[0])
+    except KeyError:
+        pass
+
+    try:
+        gps_data['altitude'] = (
+            lambda a:
+                float(a.num) / float(a.den)
+            )(tags['GPS GPSAltitude'].values[0])
+    except KeyError:
+        pass
+
+    return gps_data