Add EXIF module.
This commit is contained in:
Tom Payne
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# igc2kmz/__init__.py igc2kmz EXIF module
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# Copyright (C) 2008 Tom Payne
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import struct
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BIG_ENDIAN, = struct.unpack('=H', 'MM')
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LITTLE_ENDIAN, = struct.unpack('=H', 'II')
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BYTE_ORDER_CHAR = {BIG_ENDIAN: '>', LITTLE_ENDIAN: '<'}
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BYTE = 1
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ASCII = 2
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SHORT = 3
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LONG = 4
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RATIONAL = 5
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UNDEFINED = 7
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SLONG = 9
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SRATIONAL = 10
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DATA_TYPE_LENGTH = {BYTE: 1, ASCII: 1, SHORT: 2, LONG: 4, RATIONAL: 8, UNDEFINED: 1, SLONG: 4, SRATIONAL: 8}
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DATA_TYPE_FORMAT = {BYTE: 'B', ASCII: 'c', SHORT: 'H', LONG: 'L', RATIONAL: 'L', UNDEFINED: 'B', SLONG: 'l', SRATIONAL: 'l'}
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class SyntaxError(RuntimeError):
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pass
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class Tiff(object):
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def __init__(self, data):
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self.data = data
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self.byte_order, = struct.unpack('=H', self.data[0:2])
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if not self.byte_order in BYTE_ORDER_CHAR:
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raise SyntaxError, 'Unsupported byte order %s' % repr(self.data[6:8])
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self.byte_order_char = BYTE_ORDER_CHAR[self.byte_order]
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self.version, self.first_ifd_offset = struct.unpack(self.byte_order_char + 'HL', self.data[2:8])
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if self.version != 42:
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raise SyntaxError, 'Unsupported version %s' % self.version
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def ifd_tags(self, offset):
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n, = struct.unpack(self.byte_order_char + 'H', self.data[offset:offset + 2])
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for i in xrange(0, n):
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id, data_type, count = struct.unpack(self.byte_order_char + 'HHL', self.data[offset + 2 + 12 * i:offset + 2 + 12 * i + 8])
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if not data_type in DATA_TYPE_LENGTH:
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raise SyntaxError, 'Unrecognised data type %d' % data_type
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data_length = DATA_TYPE_LENGTH[data_type] * count
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if data_length > 4:
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data_offset, = struct.unpack(self.byte_order_char + 'L', self.data[offset + 2 + 12 * i + 8:offset + 2 + 12 * i + 12])
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data_slice = slice(data_offset, data_offset + data_length)
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else:
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data_slice = slice(offset + 2 + 12 * i + 8, offset + 2 + 12 * i + 8 + data_length)
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if data_type == ASCII:
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data = self.data[data_slice]
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else:
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if data_type == RATIONAL or data_type == SRATIONAL:
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l = struct.unpack('%s%d%s' % (self.byte_order_char, 2 * count, DATA_TYPE_FORMAT[data_type]), self.data[data_slice])
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data = zip(l[0::2], l[1::2])
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else:
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data = struct.unpack('%s%d%s' % (self.byte_order_char, count, DATA_TYPE_FORMAT[data_type]), self.data[data_slice])
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if count == 1:
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data, = data
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yield (id, data)
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def ifd_offsets(self):
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offset = self.first_ifd_offset
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while offset:
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yield offset
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n, = struct.unpack(self.byte_order_char + 'H', self.data[offset:offset + 2])
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offset, = struct.unpack(self.byte_order_char + 'H', self.data[offset + 2 + 12 * n:offset + 2 + 12 * n + 2])
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TAGS = {
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0x8769: 'ExifIFDPointer',
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0x8825: 'GPSInfoIFDPointer',
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0xa005: 'InteroperabilityIFDPointer',
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0x0100: 'ImageWidth',
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0x0101: 'ImageHeight',
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0x0102: 'BitsPerSample',
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0x0103: 'Compression',
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0x0106: 'PhotometricInterpretation',
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0x0112: 'Orientation',
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0x0115: 'SamplesPerPixel',
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0x011c: 'PlanarConfiguration',
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0x0212: 'YCbCrSubSampling',
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0x0213: 'YCbCrPositioning',
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0x011a: 'XResolution',
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0x011b: 'YResolution',
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0x0128: 'ResolutionUnit',
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0x0111: 'StripOffsets',
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0x0116: 'RowsPerStrip',
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0x0117: 'StripByteCounts',
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0x0201: 'JPEGInterchangeFormat',
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0x0202: 'JPEGInterchangeFormatLength',
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0x012d: 'TransferFunction',
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0x013e: 'WhitePoint',
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0x013f: 'PrimaryChromaticities',
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0x0211: 'YCbCrCoefficients',
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0x0214: 'ReferenceBlackWhite',
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0x0132: 'DateTime',
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0x010e: 'ImageDescription',
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0x010f: 'Make',
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0x0110: 'Model',
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0x0131: 'Software',
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0x0138: 'Artist',
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0x8298: 'Copyright',
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}
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EXIF_IFD_TAGS = {
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0x9000: 'ExifVersion',
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0xa000: 'FlashpixVersion',
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0xa001: 'ColorSpace',
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0xa002: 'PixelXDimension',
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0xa003: 'PixelYDimension',
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0x9101: 'ComponentsConfiguration',
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0x9102: 'CompressedBitsPerPixel',
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0x927c: 'MakerNote',
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0x9286: 'UserComment',
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0xa004: 'RelatedSoundFile',
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0x9003: 'DateTimeOriginal',
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0x9004: 'DateTimeDigitized',
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0x9290: 'SubsecTime',
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0x9291: 'SubsecTimeOriginal',
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0x9292: 'SubsecTimeDigitized',
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0x928a: 'ExposureTime',
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0x829d: 'FNumber',
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0x8822: 'ExposureProgram',
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0x8824: 'SpectralSensitivity',
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0x8827: 'ISOSpeedRatings',
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0x8828: 'OECF',
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0x9201: 'ShutterSpeedValue',
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0x9202: 'ApertureValue',
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0x9203: 'BrightnessValue',
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0x9204: 'ExposureBiasValue',
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0x9205: 'MaxApertureValue',
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0x9206: 'SubjectDistance',
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0x9207: 'MeteringMode',
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0x9208: 'LightSource',
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0x9209: 'Flash',
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0x9214: 'SubjectArea',
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0x920a: 'FocalLength',
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0xa20b: 'FlashEnergy',
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0xa20c: 'SpatialFrequencyResponse',
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0xa20e: 'FocalPlaneXResolution',
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0xa20f: 'FocalPlaneYResolution',
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0xa210: 'FocalPlaneResolutionUnit',
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0xa214: 'SubjectLocation',
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0xa215: 'ExposureIndex',
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0xa217: 'SensingMethod',
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0xa300: 'FileSource',
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0xa301: 'SceneType',
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0xa302: 'CFAPattern',
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0xa401: 'CustomRendered',
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0xa402: 'ExposureMode',
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0xa403: 'WhiteBalance',
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0xa404: 'DigitalZoomRatio',
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0xa405: 'FocalLengthIn35mmFilm',
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0xa406: 'SceneCaptureType',
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0xa407: 'GainControl',
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0xa408: 'Contrast',
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0xa409: 'Saturation',
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0xa40a: 'Sharpness',
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0xa40b: 'DeviceSettingDescription',
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0xa40c: 'SubjectDistanceRange',
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0xa420: 'ImageUniqueID',
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}
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GPS_INFO_IFD_TAGS = {
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0x0000: 'GPSVersionID',
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0x0001: 'GPSLatitudeRef',
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0x0002: 'GPSLatitude',
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0x0003: 'GPSLongitudeRef',
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0x0004: 'GPSLongitude',
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0x0005: 'GPSAltitudeRef',
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0x0006: 'GPSAltitude',
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0x0007: 'GPSTimeStamp',
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0x0008: 'GPSSatellites',
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0x0009: 'GPSStatus',
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0x000a: 'GPSMeasureMode',
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0x000b: 'GPSDOP',
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0x000c: 'GPSSpeedRef',
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0x000d: 'GPSSpeed',
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0x000e: 'GPSTrackRef',
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0x000f: 'GPSTrack',
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0x0010: 'GPSImgDirectionRef',
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0x0011: 'GPSImgDirection',
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0x0012: 'GPSMapDatum',
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0x0013: 'GPSDestLatitudeRef',
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0x0014: 'GPSDestLatitude',
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0x0015: 'GPSDestLongitudeRef',
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0x0016: 'GPSDestLongitude',
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0x0017: 'GPSDestBearingRef',
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0x0018: 'GPSDestBearing',
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0x0019: 'GPSDestDistanceRef',
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0x001a: 'GPSDestDistance',
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0x001b: 'GPSProcessingMethod',
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0x001c: 'GPSAreaInformation',
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0x001d: 'GPSDateStamp',
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0x001e: 'GPSDifferential',
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}
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INTEROPERABILITY_INFO_IFD_TAGS = {
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# TODO
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}
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IFD_POINTER_IDS = {
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0x8769: EXIF_IFD_TAGS,
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0x8825: GPS_INFO_IFD_TAGS,
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0xa005: INTEROPERABILITY_INFO_IFD_TAGS,
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}
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class Exif(object):
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def __init__(self, data):
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if data[0:4] != 'Exif':
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raise SyntaxError, 'Unrecognised EXIF header %s' % repr(data[0:6])
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self.tiff = Tiff(data[6:])
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def tags(self):
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result = {}
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for ifd_offset in self.tiff.ifd_offsets():
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for id, value in self.tiff.ifd_tags(ifd_offset):
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if id in IFD_POINTER_IDS:
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ifd_id = id
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for id, value in self.tiff.ifd_tags(value):
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result[IFD_POINTER_IDS[ifd_id].get(id, id)] = value
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else:
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result[TAGS.get(id, id)] = value
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return result
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SOI = 0xffd8
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EOI = 0xffd9
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APP1 = 0xffe1
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class Jpeg(object):
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def __init__(self, file):
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self.file = file
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def chunks(self):
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# FIXME The SOS (0xffda) chunk seems not to follow the spec...
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if struct.unpack('>H', self.file.read(2)) != (SOI,):
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raise SyntaxError
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id, = struct.unpack('>H', self.file.read(2))
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while id != EOI:
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size, = struct.unpack('>H', self.file.read(2))
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yield (id, self.file.read(size - 2))
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id, = struct.unpack('>H', self.file.read(2))
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def exif(self):
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for id, data in self.chunks():
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if id == APP1:
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return Exif(data)
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return None
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