import logging import struct import re from .utils import s2n_motorola, s2n_intel, Ratio from .tags import * logger = logging.getLogger('exifread') class IfdTag: """ Eases dealing with tags. """ def __init__(self, printable, tag, field_type, values, field_offset, field_length): # printable version of data self.printable = printable # tag ID number self.tag = tag # field type as index into FIELD_TYPES self.field_type = field_type # offset of start of field in bytes from beginning of IFD self.field_offset = field_offset # length of data field in bytes self.field_length = field_length # either a string or array of data items self.values = values def __str__(self): return self.printable def __repr__(self): try: s = '(0x%04X) %s=%s @ %d' % (self.tag, FIELD_TYPES[self.field_type][2], self.printable, self.field_offset) except: s = '(%s) %s=%s @ %s' % (str(self.tag), FIELD_TYPES[self.field_type][2], self.printable, str(self.field_offset)) return s class ExifHeader: """ Handle an EXIF header. """ def __init__(self, file, endian, offset, fake_exif, strict, debug=0, detailed=True): self.file = file self.endian = endian self.offset = offset self.fake_exif = fake_exif self.strict = strict self.debug = debug self.detailed = detailed self.tags = {} def s2n(self, offset, length, signed=0): """ Convert slice to integer, based on sign and endian flags. Usually this offset is assumed to be relative to the begining of the start of the EXIF information. For some cameras that use relative tags, this offset may be relative to some other starting point. """ self.file.seek(self.offset + offset) slice = self.file.read(length) if self.endian == 'I': val = s2n_intel(slice) else: val = s2n_motorola(slice) # Sign extension ? if signed: msb = 1 << (8*length-1) if val & msb: val = val-(msb << 1) return val def n2s(self, offset, length): """Convert offset to string.""" s = '' for dummy in range(length): if self.endian == 'I': s = s + chr(offset & 0xFF) else: s = chr(offset & 0xFF) + s offset = offset >> 8 return s def first_IFD(self): """Return first IFD.""" return self.s2n(4, 4) def next_IFD(self, ifd): """Return the pointer to next IFD.""" entries = self.s2n(ifd, 2) next_ifd = self.s2n(ifd+2+12*entries, 4) if next_ifd == ifd: return 0 else: return next_ifd def list_IFDs(self): """Return the list of IFDs in the header.""" i = self.first_IFD() ifds = [] while i: ifds.append(i) i = self.next_IFD(i) return ifds def dump_IFD(self, ifd, ifd_name, tag_dict=EXIF_TAGS, relative=0, stop_tag=DEFAULT_STOP_TAG): """Return a list of entries in the given IFD.""" entries = self.s2n(ifd, 2) for i in range(entries): # entry is index of start of this IFD in the file entry = ifd + 2 + 12 * i tag = self.s2n(entry, 2) # get tag name early to avoid errors, help debug tag_entry = tag_dict.get(tag) if tag_entry: tag_name = tag_entry[0] else: tag_name = 'Tag 0x%04X' % tag # ignore certain tags for faster processing if not (not self.detailed and tag in IGNORE_TAGS): field_type = self.s2n(entry + 2, 2) # unknown field type if not 0 < field_type < len(FIELD_TYPES): if not self.strict: continue else: raise ValueError('unknown type %d in tag 0x%04X' % (field_type, tag)) typelen = FIELD_TYPES[field_type][0] count = self.s2n(entry + 4, 4) # Adjust for tag id/type/count (2+2+4 bytes) # Now we point at either the data or the 2nd level offset offset = entry + 8 # If the value fits in 4 bytes, it is inlined, else we # need to jump ahead again. if count * typelen > 4: # offset is not the value; it's a pointer to the value # if relative we set things up so s2n will seek to the right # place when it adds self.offset. Note that this 'relative' # is for the Nikon type 3 makernote. Other cameras may use # other relative offsets, which would have to be computed here # slightly differently. if relative: tmp_offset = self.s2n(offset, 4) offset = tmp_offset + ifd - 8 if self.fake_exif: offset = offset + 18 else: offset = self.s2n(offset, 4) field_offset = offset values = None if field_type == 2: # special case: null-terminated ASCII string # XXX investigate # sometimes gets too big to fit in int value if count != 0: # and count < (2**31): # 2E31 is hardware dependant. --gd try: self.file.seek(self.offset + offset) values = self.file.read(count) #print values # Drop any garbage after a null. values = values.split('\x00', 1)[0] except OverflowError: values = '' else: values = [] signed = (field_type in [6, 8, 9, 10]) # XXX investigate # some entries get too big to handle could be malformed # file or problem with self.s2n if count < 1000: for dummy in range(count): if field_type in (5, 10): # a ratio value = Ratio(self.s2n(offset, 4, signed), self.s2n(offset + 4, 4, signed)) else: value = self.s2n(offset, typelen, signed) values.append(value) offset = offset + typelen # The test above causes problems with tags that are # supposed to have long values! Fix up one important case. elif tag_name in ('MakerNote', makernote.canon.CAMERA_INFO_TAG_NAME): for dummy in range(count): value = self.s2n(offset, typelen, signed) values.append(value) offset = offset + typelen #else : # print "Warning: dropping large tag:", tag, tag_name # now 'values' is either a string or an array if count == 1 and field_type != 2: printable = str(values[0]) elif count > 50 and len(values) > 20 : printable = str( values[0:20] )[0:-1] + ", ... ]" else: printable = str(values) # compute printable version of values if tag_entry: if len(tag_entry) != 1: # optional 2nd tag element is present if callable(tag_entry[1]): # call mapping function printable = tag_entry[1](values) else: printable = '' for i in values: # use lookup table for this tag printable += tag_entry[1].get(i, repr(i)) self.tags[ifd_name + ' ' + tag_name] = IfdTag(printable, tag, field_type, values, field_offset, count * typelen) logger.debug(" %s: %s", tag_name, repr(self.tags[ifd_name + ' ' + tag_name])) if tag_name == stop_tag: break def extract_tiff_thumbnail(self, thumb_ifd): """ Extract uncompressed TIFF thumbnail. Take advantage of the pre-existing layout in the thumbnail IFD as much as possible """ thumb = self.tags.get('Thumbnail Compression') if not thumb or thumb.printable != 'Uncompressed TIFF': return entries = self.s2n(thumb_ifd, 2) # this is header plus offset to IFD ... if self.endian == 'M': tiff = 'MM\x00*\x00\x00\x00\x08' else: tiff = 'II*\x00\x08\x00\x00\x00' # ... plus thumbnail IFD data plus a null "next IFD" pointer self.file.seek(self.offset + thumb_ifd) tiff += self.file.read(entries*12+2) + '\x00\x00\x00\x00' # fix up large value offset pointers into data area for i in range(entries): entry = thumb_ifd + 2 + 12 * i tag = self.s2n(entry, 2) field_type = self.s2n(entry+2, 2) typelen = FIELD_TYPES[field_type][0] count = self.s2n(entry+4, 4) oldoff = self.s2n(entry+8, 4) # start of the 4-byte pointer area in entry ptr = i * 12 + 18 # remember strip offsets location if tag == 0x0111: strip_off = ptr strip_len = count * typelen # is it in the data area? if count * typelen > 4: # update offset pointer (nasty "strings are immutable" crap) # should be able to say "tiff[ptr:ptr+4]=newoff" newoff = len(tiff) tiff = tiff[:ptr] + self.n2s(newoff, 4) + tiff[ptr+4:] # remember strip offsets location if tag == 0x0111: strip_off = newoff strip_len = 4 # get original data and store it self.file.seek(self.offset + oldoff) tiff += self.file.read(count * typelen) # add pixel strips and update strip offset info old_offsets = self.tags['Thumbnail StripOffsets'].values old_counts = self.tags['Thumbnail StripByteCounts'].values for i in range(len(old_offsets)): # update offset pointer (more nasty "strings are immutable" crap) offset = self.n2s(len(tiff), strip_len) tiff = tiff[:strip_off] + offset + tiff[strip_off + strip_len:] strip_off += strip_len # add pixel strip to end self.file.seek(self.offset + old_offsets[i]) tiff += self.file.read(old_counts[i]) self.tags['TIFFThumbnail'] = tiff def extract_jpeg_thumbnail(self): """ Extract JPEG thumbnail. (Thankfully the JPEG data is stored as a unit.) """ thumb_offset = self.tags.get('Thumbnail JPEGInterchangeFormat') if thumb_offset: self.file.seek(self.offset + thumb_offset.values[0]) size = self.tags['Thumbnail JPEGInterchangeFormatLength'].values[0] self.tags['JPEGThumbnail'] = self.file.read(size) # Sometimes in a TIFF file, a JPEG thumbnail is hidden in the MakerNote # since it's not allowed in a uncompressed TIFF IFD if 'JPEGThumbnail' not in self.tags: thumb_offset = self.tags.get('MakerNote JPEGThumbnail') if thumb_offset: self.file.seek(self.offset + thumb_offset.values[0]) self.tags['JPEGThumbnail'] = self.file.read(thumb_offset.field_length) def decode_maker_note(self): """ Decode all the camera-specific MakerNote formats Note is the data that comprises this MakerNote. The MakerNote will likely have pointers in it that point to other parts of the file. We'll use self.offset as the starting point for most of those pointers, since they are relative to the beginning of the file. If the MakerNote is in a newer format, it may use relative addressing within the MakerNote. In that case we'll use relative addresses for the pointers. As an aside: it's not just to be annoying that the manufacturers use relative offsets. It's so that if the makernote has to be moved by the picture software all of the offsets don't have to be adjusted. Overall, this is probably the right strategy for makernotes, though the spec is ambiguous. The spec does not appear to imagine that makernotes would follow EXIF format internally. Once they did, it's ambiguous whether the offsets should be from the header at the start of all the EXIF info, or from the header at the start of the makernote. """ note = self.tags['EXIF MakerNote'] # Some apps use MakerNote tags but do not use a format for which we # have a description, so just do a raw dump for these. #if self.tags.has_key('Image Make'): make = self.tags['Image Make'].printable #else: # make = '' # model = self.tags['Image Model'].printable # unused # Nikon # The maker note usually starts with the word Nikon, followed by the # type of the makernote (1 or 2, as a short). If the word Nikon is # not at the start of the makernote, it's probably type 2, since some # cameras work that way. if 'NIKON' in make: if note.values[0:7] == [78, 105, 107, 111, 110, 0, 1]: logger.debug("Looks like a type 1 Nikon MakerNote.") self.dump_IFD(note.field_offset+8, 'MakerNote', tag_dict=makernote.NIKON_OLD) elif note.values[0:7] == [78, 105, 107, 111, 110, 0, 2]: if self.debug: logger.debug("Looks like a labeled type 2 Nikon MakerNote") if note.values[12:14] != [0, 42] and note.values[12:14] != [42, 0]: raise ValueError("Missing marker tag '42' in MakerNote.") # skip the Makernote label and the TIFF header self.dump_IFD(note.field_offset+10+8, 'MakerNote', tag_dict=makernote.NIKON_NEW, relative=1) else: # E99x or D1 logger.debug("Looks like an unlabeled type 2 Nikon MakerNote") self.dump_IFD(note.field_offset, 'MakerNote', tag_dict=makernote.NIKON_NEW) return # Olympus if make.startswith('OLYMPUS'): self.dump_IFD(note.field_offset+8, 'MakerNote', tag_dict=makernote.OLYMPUS) # TODO #for i in (('MakerNote Tag 0x2020', makernote.OLYMPUS_TAG_0x2020),): # self.decode_olympus_tag(self.tags[i[0]].values, i[1]) #return # Casio if 'CASIO' in make or 'Casio' in make: self.dump_IFD(note.field_offset, 'MakerNote', tag_dict=makernote.CASIO) return # Fujifilm if make == 'FUJIFILM': # bug: everything else is "Motorola" endian, but the MakerNote # is "Intel" endian endian = self.endian self.endian = 'I' # bug: IFD offsets are from beginning of MakerNote, not # beginning of file header offset = self.offset self.offset += note.field_offset # process note with bogus values (note is actually at offset 12) self.dump_IFD(12, 'MakerNote', tag_dict=makernote.FUJIFILM) # reset to correct values self.endian = endian self.offset = offset return # Canon if make == 'Canon': self.dump_IFD(note.field_offset, 'MakerNote', tag_dict=makernote.canon.TAGS) for i in (('MakerNote Tag 0x0001', makernote.canon.CAMERA_SETTINGS), ('MakerNote Tag 0x0002', makernote.canon.FOCAL_LENGTH), ('MakerNote Tag 0x0004', makernote.canon.SHOT_INFO), ('MakerNote Tag 0x0026', makernote.canon.AF_INFO_2), ('MakerNote Tag 0x0093', makernote.canon.FILE_INFO)): if i[0] in self.tags: logger.debug('Canon ' + i[0]) self.canon_decode_tag(self.tags[i[0]].values, i[1]) del self.tags[i[0]] if makernote.canon.CAMERA_INFO_TAG_NAME in self.tags: tag = self.tags[makernote.canon.CAMERA_INFO_TAG_NAME] logger.debug('Canon CameraInfo') self.canon_decode_camera_info(tag) del self.tags[makernote.canon.CAMERA_INFO_TAG_NAME] return def olympus_decode_tag(self, value, mn_tags): """ TODO Decode Olympus MakerNote tag based on offset within tag.""" pass def canon_decode_tag(self, value, mn_tags): """ Decode Canon MakerNote tag based on offset within tag. See http://www.burren.cx/david/canon.html by David Burren """ for i in range(1, len(value)): tag = mn_tags.get(i, ('Unknown', )) name = tag[0] if len(tag) > 1: val = tag[1].get(value[i], 'Unknown') else: val = value[i] try: logger.debug(" %s %s %s", i, name, hex(value[i])) except TypeError: logger.debug(" %s %s %s", i, name, value[i]) # it's not a real IFD Tag but we fake one to make everybody # happy. this will have a "proprietary" type self.tags['MakerNote ' + name] = IfdTag(str(val), None, 0, None, None, None) def canon_decode_camera_info(self, camera_info_tag): """Decode the variable length encoded camera info section.""" model = self.tags.get('Image Model', None) if not model: return model = str(model.values) camera_info_tags = None for (model_name_re, tag_desc) in \ makernote.canon.CAMERA_INFO_MODEL_MAP.items(): if re.search(model_name_re, model): camera_info_tags = tag_desc break else: return # We are assuming here that these are all unsigned bytes (Byte or # Unknown) if camera_info_tag.field_type not in (1, 7): return camera_info = struct.pack('<%dB' % len(camera_info_tag.values), *camera_info_tag.values) # Look for each data value and decode it appropriately. for offset, tag in camera_info_tags.items(): tag_format = tag[1] tag_size = struct.calcsize(tag_format) if len(camera_info) < offset + tag_size: continue packed_tag_value = camera_info[offset:offset+tag_size] tag_value = struct.unpack(tag_format, packed_tag_value)[0] tag_name = tag[0] if len(tag) > 2: if callable(tag[2]): tag_value = tag[2](tag_value) else: tag_value = tag[2].get(tag_value, tag_value) logger.debug(" %s %s", tag_name, tag_value) self.tags['MakerNote ' + tag_name] = IfdTag(str(tag_value), None, 0, None, None, None)