geotag action crash when trying to write the Exif_GPSInfo_GPSAltitudeRef tag

[Ruben]

source package:
**************
phatch-cli

ubuntu release:
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Description: Ubuntu 14.04 LTS
Release: 14.04

version:
*******
phatch:
  Instalados: 0.2.7.1-3
  Candidato: 0.2.7.1-3
  Tabla de versión:
 *** 0.2.7.1-3 0
        500 http://es.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
        100 /var/lib/dpkg/status

When trying to assing goetags to photos using a GARMIN GPX file y get this error for every photo (spanish version, sorry) and no geotag is modified:

Error 0:No se puede aplicar la acción Geoetiqueta a la imagen 'photo.JPG' en la carpeta:
/Testing/PhotoFolder

u'Imposible escribir marca "Exif_GPSInfo_GPSAltitudeRef":\nInvalid value for EXIF type [Byte]: [0]'

Action:{'fields': {'GPS Data (gpx)': u'/GPSTrack.gpx',
            'GPS Report (csv)': ' ',
            'Time Shift (seconds)': u'60',
            '__enabled__': 'yes'},
 'label': 'Geotag'}

Traceback (most recent call last):
  File "/usr/share/phatch/phatch/core/api.py", line 614, in apply_action_to_photo
    photo = action.apply(photo, read_only_settings, cache)
  File "/usr/share/phatch/phatch/actions/geotag.py", line 75, in apply
    info[key.replace('.', '_')] = value # writable
  File "/usr/share/phatch/phatch/core/pil.py", line 365, in __setitem__
    % (_('Impossible to write tag "%s"') % tag, message))
KeyError: u'Imposible escribir marca "Exif_GPSInfo_GPSAltitudeRef":\nInvalid value for EXIF type [Byte]: [0]'
*

The problem is that 'Exif_GPSInfo_GPSAltitudeRef' tag uses a byte type value while phatch is trying to write a int type value (eleR):

---------------------------------------------------------
in GPS.py at line 203

    latR = 'N'
    lonR = 'E'
    eleR = 0
    if lat < 0:
        lat = -lat
        latR = 'S'
    if lon < 0:
        lon = -lon
        lonR = 'W'
    sele = "%6.1f" % (ele)
    if ele < 0:
        ele = -ele
        eleR = 1

    slat = "%02d.%02d'" '%02d"%s' % (d(lat), m(lat), s(lat), latR)
    slon = "%02d.%02d'" '%02d"%s' % (d(lon), m(lon), s(lon), lonR)
    if report:
        report.write(",".join([stamp, timestamp, slat, slon, sele, path])\
            + "\n")
    # get Rational number for ele
    # don't know why r(ele) is causing trouble!
    # it might be that the denominator is overflowing 32 bits!
    # and this would also import lat and lon
    rele = pyexiv2.Rational(int(ele * 10.0), 10)
    # create and return the dictionary of tags to be added to the image
    metadata = {}
    metadata['Exif_GPSInfo_GPSAltitude'] = rele
    metadata['Exif_GPSInfo_GPSAltitudeRef'] = eleR:
---------------------------------------------------------

I have solved the problem by transforming eleR to byte with the bytes() constructor:

metadata['Exif_GPSInfo_GPSAltitudeRef'] = bytes(eleR)