exif.py

from __future__ import division

import datetime
import exifread
import logging
import xmltodict as x2d
from codecs import encode, decode

from six import string_types

from opensfm.sensors import sensor_data
from opensfm import types
from opensfm import pygeometry


logger = logging.getLogger(__name__)

inch_in_mm = 25.4
cm_in_mm = 10
um_in_mm = 0.001
default_projection = 'perspective'


def eval_frac(value):
    try:
        return float(value.num) / float(value.den)
    except ZeroDivisionError:
        return None


def gps_to_decimal(values, reference):
    sign = 1 if reference in 'NE' else -1
    degrees = eval_frac(values[0])
    minutes = eval_frac(values[1])
    seconds = eval_frac(values[2])
    return sign * (degrees + minutes / 60 + seconds / 3600)


def get_tag_as_float(tags, key, index=0):
    if key in tags:
        val = tags[key].values[index]
        if isinstance(val, exifread.utils.Ratio):
            ret_val = eval_frac(val)
            if ret_val is None:
                logger.error(
                    'The rational "{2}" of tag "{0:s}" at index {1:d} c'
                    'aused a division by zero error'.format(
                        key, index, val))
            return ret_val
        else:
            return float(val)
    else:
        return None


def compute_focal(focal_35, focal, sensor_width, sensor_string):
    if focal_35 is not None and focal_35 > 0:
        focal_ratio = focal_35 / 36.0  # 35mm film produces 36x24mm pictures.
    else:
        if not sensor_width:
            sensor_width = sensor_data.get(sensor_string, None)
        if sensor_width and focal:
            focal_ratio = focal / sensor_width
            focal_35 = 36.0 * focal_ratio
        else:
            focal_35 = 0
            focal_ratio = 0
    return focal_35, focal_ratio


def sensor_string(make, model):
    if make != 'unknown':
        # remove duplicate 'make' information in 'model'
        model = model.replace(make, '')
    return (make.strip() + ' ' + model.strip()).strip().lower()


def camera_id(exif):
    return camera_id_(exif['make'], exif['model'],
                      exif['width'], exif['height'],
                      exif['projection_type'], exif['focal_ratio'])


def camera_id_(make, model, width, height, projection_type, focal):
    if make != 'unknown':
        # remove duplicate 'make' information in 'model'
        model = model.replace(make, '')
    return ' '.join([
        'v2',
        make.strip(),
        model.strip(),
        str(int(width)),
        str(int(height)),
        projection_type,
        str(focal)[:6],
    ]).lower()


def extract_exif_from_file(fileobj):
    if isinstance(fileobj, string_types):
        with open(fileobj) as f:
            exif_data = EXIF(f)
    else:
        exif_data = EXIF(fileobj)

    d = exif_data.extract_exif()
    return d


def unescape_string(s):
    return decode(encode(s, 'latin-1', 'backslashreplace'), 'unicode-escape')


def parse_xmp_string(xmp_str):
    for _ in range(2):
        try:
            return x2d.parse(xmp_str)
        except:
            xmp_str = unescape_string(xmp_str)
    return None


def get_xmp(fileobj):
    '''Extracts XMP metadata from and image fileobj
    '''
    img_str = str(fileobj.read())
    xmp_start = img_str.find('<x:xmpmeta')
    xmp_end = img_str.find('</x:xmpmeta')

    if xmp_start < xmp_end:
        xmp_str = img_str[xmp_start:xmp_end + 12]
        xdict = parse_xmp_string(xmp_str)
        if xdict is None:
            return []
        xdict = xdict.get('x:xmpmeta', {})
        xdict = xdict.get('rdf:RDF', {})
        xdict = xdict.get('rdf:Description', {})
        if isinstance(xdict, list):
            return xdict
        else:
            return [xdict]
    else:
        return []


def get_gpano_from_xmp(xmp):
    for i in xmp:
        for k in i:
            if 'GPano' in k:
                return i
    return {}


class EXIF:
    def __init__(self, fileobj):
        self.fileobj = fileobj
        self.tags = exifread.process_file(fileobj, details=False)
        fileobj.seek(0)
        self.xmp = get_xmp(fileobj)

    def extract_image_size(self):
        # Image Width and Image Height
        if ('EXIF ExifImageWidth' in self.tags and # PixelXDimension
                'EXIF ExifImageLength' in self.tags):  # PixelYDimension
            width, height = (int(self.tags['EXIF ExifImageWidth'].values[0]),
                             int(self.tags['EXIF ExifImageLength'].values[0]))
        elif ('Image ImageWidth' in self.tags and
              'Image ImageLength' in self.tags):
            width, height = (int(self.tags['Image ImageWidth'].values[0]),
                             int(self.tags['Image ImageLength'].values[0]))
        else:
            width, height = -1, -1
        return width, height

    def _decode_make_model(self, value):
        """Python 2/3 compatible decoding of make/model field."""
        if hasattr(value, 'decode'):
            try:
                return value.decode('utf-8')
            except UnicodeDecodeError:
                return 'unknown'
        else:
            return value

    def extract_make(self):
        # Camera make and model
        if 'EXIF LensMake' in self.tags:
            make = self.tags['EXIF LensMake'].values
        elif 'Image Make' in self.tags:
            make = self.tags['Image Make'].values
        else:
            make = 'unknown'
        return self._decode_make_model(make)

    def extract_model(self):
        if 'EXIF LensModel' in self.tags:
            model = self.tags['EXIF LensModel'].values
        elif 'Image Model' in self.tags:
            model = self.tags['Image Model'].values
        else:
            model = 'unknown'
        return self._decode_make_model(model)

    def extract_projection_type(self):
        gpano = get_gpano_from_xmp(self.xmp)
        return gpano.get('GPano:ProjectionType', 'perspective')

    def extract_focal(self):
        make, model = self.extract_make(), self.extract_model()
        focal_35, focal_ratio = compute_focal(
            get_tag_as_float(self.tags, 'EXIF FocalLengthIn35mmFilm'),
            get_tag_as_float(self.tags, 'EXIF FocalLength'),
            self.extract_sensor_width(),
            sensor_string(make, model))
        return focal_35, focal_ratio

    def extract_sensor_width(self):
        """Compute sensor with from width and resolution."""
        if ('EXIF FocalPlaneResolutionUnit' not in self.tags or
                'EXIF FocalPlaneXResolution' not in self.tags):
            return None
        resolution_unit = self.tags['EXIF FocalPlaneResolutionUnit'].values[0]
        mm_per_unit = self.get_mm_per_unit(resolution_unit)
        if not mm_per_unit:
            return None
        pixels_per_unit = get_tag_as_float(self.tags, 'EXIF FocalPlaneXResolution')
        if pixels_per_unit <= 0:
            pixels_per_unit = get_tag_as_float(self.tags, 'EXIF FocalPlaneYResolution')
            if pixels_per_unit <= 0:
                return None
        units_per_pixel = 1 / pixels_per_unit
        width_in_pixels = self.extract_image_size()[0]
        return width_in_pixels * units_per_pixel * mm_per_unit

    def get_mm_per_unit(self, resolution_unit):
        """Length of a resolution unit in millimeters.

        Uses the values from the EXIF specs in
        https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/EXIF.html

        Args:
            resolution_unit: the resolution unit value given in the EXIF
        """
        if resolution_unit == 2:    # inch
            return inch_in_mm
        elif resolution_unit == 3:  # cm
            return cm_in_mm
        elif resolution_unit == 4:  # mm
            return 1
        elif resolution_unit == 5:  # um
            return um_in_mm
        else:
            logger.warning('Unknown EXIF resolution unit value: {}'.format(resolution_unit))
            return None

    def extract_orientation(self):
        orientation = 1
        if 'Image Orientation' in self.tags:
            value = self.tags.get('Image Orientation').values[0]
            if type(value) == int:
                orientation = value
        return orientation

    def extract_ref_lon_lat(self):
        if 'GPS GPSLatitudeRef' in self.tags:
            reflat = self.tags['GPS GPSLatitudeRef'].values
        else:
            reflat = 'N'
        if 'GPS GPSLongitudeRef' in self.tags:
            reflon = self.tags['GPS GPSLongitudeRef'].values
        else:
            reflon = 'E'
        return reflon, reflat

    def extract_dji_lon_lat(self):
        lon = self.xmp[0]['@drone-dji:Longitude']
        lat = self.xmp[0]['@drone-dji:Latitude']
        lon_number = float(lon[1:])
        lat_number = float(lat[1:])
        lon_number = lon_number if lon[0] == '+' else -lon_number
        lat_number = lat_number if lat[0] == '+' else -lat_number
        return lon_number, lat_number

    def extract_dji_altitude(self):
        return float(self.xmp[0]['@drone-dji:AbsoluteAltitude'])

    def has_dji_xmp(self):
        return (len(self.xmp) > 0) and ('@drone-dji:Latitude' in self.xmp[0])

    def extract_lon_lat(self):
        if self.has_dji_xmp():
            lon, lat = self.extract_dji_lon_lat()
        elif 'GPS GPSLatitude' in self.tags:
            reflon, reflat = self.extract_ref_lon_lat()
            lat = gps_to_decimal(self.tags['GPS GPSLatitude'].values, reflat)
            lon = gps_to_decimal(self.tags['GPS GPSLongitude'].values, reflon)
        else:
            lon, lat = None, None
        return lon, lat

    def extract_altitude(self):
        if self.has_dji_xmp():
            altitude = self.extract_dji_altitude()
        elif 'GPS GPSAltitude' in self.tags:
            altitude = eval_frac(self.tags['GPS GPSAltitude'].values[0])
        else:
            altitude = None
        return altitude

    def extract_dop(self):
        if 'GPS GPSDOP' in self.tags:
            dop = eval_frac(self.tags['GPS GPSDOP'].values[0])
        else:
            dop = None
        return dop

    def extract_geo(self):
        altitude = self.extract_altitude()
        dop = self.extract_dop()
        lon, lat = self.extract_lon_lat()
        d = {}

        if lon is not None and lat is not None:
            d['latitude'] = lat
            d['longitude'] = lon
        if altitude is not None:
            d['altitude'] = altitude
        if dop is not None:
            d['dop'] = dop
        return d

    def extract_capture_time(self):
        if ('GPS GPSDate' in self.tags and  # Actually GPSDateStamp
                'GPS GPSTimeStamp' in self.tags):
            try:
                hours = int(get_tag_as_float(self.tags, 'GPS GPSTimeStamp', 0))
                minutes = int(get_tag_as_float(self.tags, 'GPS GPSTimeStamp', 1))
                seconds = get_tag_as_float(self.tags, 'GPS GPSTimeStamp', 2)
                gps_timestamp_string = ('{0:s} {1:02d}:{2:02d}:{3:02f}'.format(
                    self.tags['GPS GPSDate'].values,
                    hours,
                    minutes,
                    seconds))
                return (datetime.datetime.strptime(
                    gps_timestamp_string, '%Y:%m:%d %H:%M:%S.%f') -
                    datetime.datetime(1970, 1, 1)).total_seconds()
            except (TypeError, ValueError):
                logger.info(
                    'The GPS time stamp in image file "{0:s}" is invalid. '
                    'Falling back to DateTime*'.format(self.fileobj.name))

        time_strings = [('EXIF DateTimeOriginal', 'EXIF SubSecTimeOriginal', 'EXIF Tag 0x9011'),
                        ('EXIF DateTimeDigitized', 'EXIF SubSecTimeDigitized', 'EXIF Tag 0x9012'),
                        ('Image DateTime', 'Image SubSecTime', 'Image Tag 0x9010')]
        for datetime_tag, subsec_tag, offset_tag in time_strings:
            if datetime_tag in self.tags:
                date_time = self.tags[datetime_tag].values
                if subsec_tag in self.tags:
                    subsec_time = self.tags[subsec_tag].values
                else:
                    subsec_time = '0'
                try:
                    s = '{0:s}.{1:s}'.format(date_time, subsec_time)
                    d = datetime.datetime.strptime(s, '%Y:%m:%d %H:%M:%S.%f')
                except ValueError:
                    logger.debug(
                        'The "{1:s}" time stamp or \"{2:s}\" tag is invalid in '
                        'image file "{0:s}"'.format(
                            self.fileobj.name, datetime_tag, subsec_tag))
                    continue
                # Test for OffsetTimeOriginal | OffsetTimeDigitized | OffsetTime
                if offset_tag in self.tags:
                    offset_time = self.tags[offset_tag].values
                    try:
                        d += datetime.timedelta(hours=-int(offset_time[0:3]),
                                                minutes=int(offset_time[4:6]))
                    except (TypeError, ValueError):
                        logger.debug(
                            'The "{0:s}" time zone offset in image file "{1:s}"'
                            ' is invalid'.format(
                                offset_tag, self.fileobj.name))
                        logger.debug(
                            'Naively assuming UTC on "{0:s}" in image file '
                            '"{1:s}"'.format(datetime_tag, self.fileobj.name))
                else:
                    logger.debug(
                        'No GPS time stamp and no time zone offset in image '
                        'file "{0:s}"'.format(self.fileobj.name))
                    logger.debug(
                        'Naively assuming UTC on "{0:s}" in image file "{1:s}"'
                        .format(datetime_tag, self.fileobj.name))
                return (d - datetime.datetime(1970, 1, 1)).total_seconds()
        logger.info(
            'Image file "{0:s}" has no valid time stamp'.format(
                self.fileobj.name))
        return 0.0

    def extract_exif(self):
        width, height = self.extract_image_size()
        projection_type = self.extract_projection_type()
        focal_35, focal_ratio = self.extract_focal()
        make, model = self.extract_make(), self.extract_model()
        orientation = self.extract_orientation()
        geo = self.extract_geo()
        capture_time = self.extract_capture_time()
        d = {
            'make': make,
            'model': model,
            'width': width,
            'height': height,
            'projection_type': projection_type,
            'focal_ratio': focal_ratio,
            'orientation': orientation,
            'capture_time': capture_time,
            'gps': geo
        }
        d['camera'] = camera_id(d)
        return d


def hard_coded_calibration(exif):
    focal = exif['focal_ratio']
    fmm35 = int(round(focal * 36.0))
    make = exif['make'].strip().lower()
    model = exif['model'].strip().lower()
    if 'gopro' in make:
        if fmm35 == 20:
            # GoPro Hero 3, 7MP medium
            return {'focal': focal, 'k1': -0.37, 'k2': 0.28}
        elif fmm35 == 15:
            # GoPro Hero 3, 7MP wide
            # "v2 gopro hero3+ black edition 3000 2250 perspective 0.4166"
            return {'focal': 0.466, 'k1': -0.195, 'k2': 0.030}
        elif fmm35 == 23:
            # GoPro Hero 2, 5MP medium
            return {'focal': focal, 'k1': -0.38, 'k2': 0.24}
        elif fmm35 == 16:
            # GoPro Hero 2, 5MP wide
            return {'focal': focal, 'k1': -0.39, 'k2': 0.22}
    elif 'bullet5s' in make:
        return {'focal': 0.57, 'k1': -0.30, 'k2': 0.06}
    elif 'garmin' == make:
        if 'virb' == model:
            # "v2 garmin virb 4608 3456 perspective 0"
            return {'focal': 0.5, 'k1': -0.08, 'k2': 0.005}
        elif 'virbxe' == model:
            # "v2 garmin virbxe 3477 1950 perspective 0.3888"
            # "v2 garmin virbxe 1600 1200 perspective 0.3888"
            # "v2 garmin virbxe 4000 3000 perspective 0.3888"
            # Calibration when using camera's undistortion
            return {'focal': 0.466, 'k1': -0.08, 'k2': 0.0}
            # Calibration when not using camera's undistortion
            # return {'focal': 0.466, 'k1': -0.195, 'k2'; 0.030}
    elif 'drift' == make:
        if 'ghost s' == model:
            return {'focal': 0.47, 'k1': -0.22, 'k2': 0.03}
    elif 'xiaoyi' in make:
        return {'focal': 0.5, 'k1': -0.19, 'k2': 0.028}
    elif 'geo' == make and 'frames' == model:
        return {'focal': 0.5, 'k1': -0.24, 'k2': 0.04}
    elif 'sony' == make:
        if 'hdr-as200v' == model:
            return {'focal': 0.55, 'k1': -0.30, 'k2': 0.08}
        elif 'hdr-as300' in model:
            return {"focal":  0.3958, "k1": -0.1496, "k2": 0.0201}


def focal_ratio_calibration(exif):
    if exif.get('focal_ratio'):
        return {
            'focal': exif['focal_ratio'],
            'k1': 0.0,
            'k2': 0.0,
            'p1': 0.0,
            'p2': 0.0,
            'k3': 0.0
        }


def focal_xy_calibration(exif):
    focal = exif.get('focal_x', exif.get('focal_ratio'))
    if focal:
        return {
            'focal_x': focal,
            'focal_y': focal,
            'c_x': exif.get('c_x', 0.0),
            'c_y': exif.get('c_y', 0.0),
            'k1': 0.0,
            'k2': 0.0,
            'p1': 0.0,
            'p2': 0.0,
            'k3': 0.0
        }


def default_calibration(data):
    return {
        'focal': data.config['default_focal_prior'],
        'focal_x': data.config['default_focal_prior'],
        'focal_y': data.config['default_focal_prior'],
        'c_x': 0.0,
        'c_y': 0.0,
        'k1': 0.0,
        'k2': 0.0,
        'p1': 0.0,
        'p2': 0.0,
        'k3': 0.0
    }


def calibration_from_metadata(metadata, data):
    """Finds the best calibration in one of the calibration sources."""
    pt = metadata.get('projection_type', default_projection).lower()
    if pt == 'brown':
        calib = (hard_coded_calibration(metadata)
                 or focal_xy_calibration(metadata)
                 or default_calibration(data))
    else:
        calib = (hard_coded_calibration(metadata)
                 or focal_ratio_calibration(metadata)
                 or default_calibration(data))
    calib['projection_type'] = pt
    return calib


def camera_from_exif_metadata(metadata, data,
                              calibration_func=calibration_from_metadata):
    '''
    Create a camera object from exif metadata and the calibration
    function that turns metadata into usable calibration parameters.
    '''

    calib = calibration_func(metadata, data)
    calib_pt = calib.get('projection_type', default_projection).lower()

    camera = None
    if calib_pt == 'perspective':
        camera = pygeometry.Camera.create_perspective(
            calib['focal'], calib['k1'], calib['k2'])
    elif calib_pt == 'brown':
        camera = pygeometry.Camera.create_brown(
            calib['focal_x'], calib['focal_y'] / calib['focal_x'],
            [calib['c_x'], calib['c_y']],
            [calib['k1'], calib['k3'], calib['k3'],
             calib['p1'], calib['p2']])
    elif calib_pt == 'fisheye':
        camera = pygeometry.Camera.create_fisheye(
            calib['focal'], calib['k1'], calib['k2'])
    elif calib_pt == 'dual':
        camera = pygeometry.Camera.create_dual(
            calib['transition'], calib['focal'], calib['k1'], calib['k2'])
    elif calib_pt in ['equirectangular', 'spherical']:
        camera = pygeometry.Camera.create_spherical()
    else:
        raise ValueError("Unknown projection type: {}".format(pt))

    camera.id = metadata['camera']
    camera.width = metadata['width']
    camera.height = metadata['height']
    return camera