terom@102: """
terom@102:     A custom EXIF parsing module, aimed at high performance.
terom@102: """
terom@102: 
terom@102: import struct, mmap, os
terom@102: 
terom@102: def read_struct (file, fmt) :
terom@102:     """
terom@102:         Utility function to read data from the a file using struct
terom@102:     """
terom@102:     
terom@102:     # length of data
terom@102:     fmt_size = struct.calcsize(fmt)
terom@102:     
terom@102:     # get data
terom@102:     file_data = file.read(fmt_size)
terom@102:     
terom@102:     # unpack single item, this should raise an error if file_data is too short
terom@102:     return struct.unpack(fmt, file_data)
terom@102: 
terom@102: class Buffer (object) :
terom@102:     """
terom@102:         Wraps a buffer object (anything that supports the python buffer protocol) for read-only access.
terom@102:         
terom@102:         Includes an offset for relative values, and an endianess for reading binary data.
terom@102:     """
terom@102:     
terom@102:     def __init__ (self, obj, offset=None, size=None, struct_prefix='=') :
terom@102:         """
terom@102:             Create a new Buffer object with a new underlying buffer, created from the given object, offset and size.
terom@102:             
terom@102:             The endiannes is given in the form of a struct-module prefix, which should be one of '<' or '>'.
terom@102:             Standard size/alignment are assumed.
terom@102:         """
terom@102: 
terom@102:         # store
terom@103:         self.buf = buffer(obj, *(arg for arg in (offset, size) if arg is not None))
terom@102:         self.offset = offset
terom@102:         self.size = size
terom@102:         self.prefix = struct_prefix
terom@102:     
terom@102:     def subregion (self, offset, length=None) :
terom@102:         """
terom@102:             Create a new sub-Buffer referencing a view of this buffer, at the given offset, and with the given
terom@102:             length, if any, and the same struct_prefix.
terom@102:         """
terom@102: 
terom@102:         return Buffer(self.buf, offset, length, struct_prefix=self.prefix)
terom@102:     
terom@102:     def pread (self, offset, length) :
terom@102:         """
terom@102:             Read a random-access region of raw data
terom@102:         """
terom@102: 
terom@102:         return self.buf[offset:offset + length]
terom@102:     
terom@102:     def pread_struct (self, offset, fmt) :
terom@102:         """
terom@102:             Read structured data using the given struct format from the given offset.
terom@102:         """
terom@102: 
terom@102:         return struct.unpack_from(self.prefix + fmt, self.buf, offset=offset)
terom@102: 
terom@102:     def pread_item (self, offset, fmt) :
terom@102:         """
terom@102:             Read a single item of structured data from the given offset.
terom@102:         """
terom@102: 
terom@102:         value, = self.pread_struct(offset, fmt)
terom@102: 
terom@102:         return value
terom@102: 
terom@102:     def iter_offsets (self, count, size, offset=0) :
terom@102:         """
terom@102:             Yield a series of offsets for `count` items of `size` bytes, beginning at `offset`.
terom@102:         """
terom@102: 
terom@102:         return xrange(offset, offset + count * size, size)
terom@102:     
terom@102:     def item_size (self, fmt) :
terom@102:         """
terom@102:             Returns the size in bytes of the given item format
terom@102:         """
terom@102: 
terom@102:         return struct.calcsize(self.prefix + fmt)
terom@102: 
terom@102:     def unpack_item (self, fmt, data) :
terom@102:         """
terom@102:             Unpacks a single item from the given data
terom@102:         """
terom@102: 
terom@102:         value, = struct.unpack(self.prefix + fmt, data)
terom@102:         
terom@102:         return value
terom@102: 
terom@102: def mmap_buffer (file, size) :
terom@102:     """
terom@102:         Create and return a new read-only mmap'd region
terom@102:     """
terom@102: 
terom@102:     return mmap.mmap(file.fileno(), size, access=mmap.ACCESS_READ)
terom@102: 
terom@102: import exif_data
terom@102: 
terom@102: class Tag (object) :
terom@102:     """
terom@102:         Represents a single Tag in an IFD
terom@102:     """
terom@102: 
terom@103:     def __init__ (self, offset, tag, type, count, data_raw) :
terom@102:         """
terom@102:             Build a Tag with the given binary items from the IFD entry
terom@102:         """
terom@102:         
terom@102:         self.offset = offset
terom@102:         self.tag = tag
terom@102:         self.type = type
terom@102:         self.count = count
terom@103:         self.data_raw = data_raw
terom@102:         
terom@102:         # lookup the type for this tag
terom@102:         self.type_data = exif_data.FIELD_TYPES.get(type)
terom@102: 
terom@102:         # unpack it
terom@102:         if self.type_data :
terom@103:             self.type_format, self.type_name, self.type_func = self.type_data
terom@102:     
terom@102:         # lookup the tag data for this tag
terom@102:         self.tag_data = exif_data.EXIF_TAGS.get(tag)
terom@102:         
terom@102:         # unpack it
terom@102:         if self.tag_data :
terom@102:             # the EXIF tag name
terom@104:             self.tag_name, self.tag_value_spec = self.tag_data
terom@102:             
terom@102:     @property
terom@102:     def name (self) :
terom@102:         """
terom@102:             Lookup the name of this tag via its code, returns None if unknown.
terom@102:         """
terom@102: 
terom@102:         if self.tag_data :
terom@102:             return self.tag_name
terom@102: 
terom@102:         else :
terom@102:             return None
terom@102:     
terom@103:     def process_values (self, raw_values) :
terom@103:         """
terom@103:             Process the given raw values unpacked from the file.
terom@103:         """
terom@103: 
terom@103:         if self.type_data and self.type_func :
terom@103:             # use the filter func
terom@103:             return self.type_func(raw_values)
terom@103: 
terom@103:         else :
terom@103:             # nada, just leave them
terom@103:             return raw_values
terom@103: 
terom@104:     def readable_value (self, values) :
terom@102:         """
terom@104:             Convert the given values for this tag into a human-readable string.
terom@102: 
terom@104:             Returns the comma-separated values by default.
terom@102:         """
terom@102: 
terom@104:         if self.tag_data :
terom@104:             spec = self.tag_value_spec
terom@102: 
terom@102:         else :
terom@104:             # fallback to default
terom@104:             spec = None
terom@104: 
terom@104:         # map it
terom@104:         return exif_data.map_values(spec, values)
terom@102: 
terom@102: # size of an IFD entry in bytes
terom@102: IFD_ENTRY_SIZE = 12
terom@102: 
terom@102: class IFD (Buffer) :
terom@102:     """
terom@102:         Represents an IFD (Image file directory) region in EXIF data.
terom@102:     """
terom@102: 
terom@102:     def __init__ (self, buffer, **buffer_opts) :
terom@102:         """
terom@102:             Access the IFD data from the given bufferable object with given buffer opts.
terom@102: 
terom@102:             This will read the `count` and `next_offset` values.
terom@102:         """
terom@102: 
terom@102:         # init
terom@102:         super(IFD, self).__init__(buffer, **buffer_opts)
terom@102:         
terom@102:         # read header
terom@102:         self.count = self.pread_item(0, 'H')
terom@102: 
terom@102:         # read next-offset
terom@102:         self.next_offset = self.pread_item(0x02 + self.count * IFD_ENTRY_SIZE, 'I')
terom@102:     
terom@102:     def iter_tags (self) :
terom@102:         """
terom@102:             Iterate over all the Tag objects in this IFD
terom@102:         """
terom@102:         
terom@102:         # read each tag
terom@102:         for offset in self.iter_offsets(self.count, IFD_ENTRY_SIZE, 0x02) :
terom@102:             # read the tag data
terom@103:             tag, type, count, data_raw = self.pread_struct(offset, 'HHI4s')
terom@102:             
terom@102:             # yield the new Tag
terom@103:             yield Tag(offset, tag, type, count, data_raw)
terom@102: 
terom@102: class EXIF (Buffer) :
terom@102:     """
terom@102:         Represents the EXIF data embedded in some image file in the form of a Region.
terom@102:     """
terom@102: 
terom@102:     def __init__ (self, buffer, tags=None, **buffer_opts) :
terom@102:         """
terom@102:             Access the EXIF data from the given bufferable object with the given buffer options.
terom@102: 
terom@102:             `tags`, if given, specifies that only the given named tags should be loaded.
terom@102:         """
terom@102: 
terom@102:         # init Buffer
terom@102:         super(EXIF, self).__init__(buffer, **buffer_opts)
terom@102: 
terom@102:         # store
terom@102:         self.buffer = buffer
terom@102:     
terom@102:     def iter_ifds (self) :
terom@102:         """
terom@104:             Iterate over the primary IFDs in this EXIF.
terom@102:         """
terom@102: 
terom@102:         # starting offset
terom@102:         offset = self.pread_item(0x04, 'I')
terom@102: 
terom@102:         while offset :
terom@103:             # create and read the IFD, operating on the right sub-buffer
terom@103:             ifd = IFD(self.buf, offset=offset)
terom@102: 
terom@102:             # yield it
terom@102:             yield ifd
terom@102: 
terom@102:             # skip to next offset
terom@102:             offset = ifd.next_offset
terom@102:     
terom@104:     def iter_all_ifds (self) :
terom@104:         """
terom@104:             Iterate over all of the IFDs contained within this EXIF, or within other IFDs.
terom@104:         """
terom@104: 
terom@102:     __iter__ = iter_ifds
terom@102:     
terom@103:     def tag_data_info (self, tag) :
terom@103:         """
terom@103:             Calculate the location, format and size of the given tag's data.
terom@103: 
terom@103:             Returns a (fmt, offset, size) tuple.
terom@103:         """
terom@103:         # unknown tag?
terom@103:         if not tag.type_data :
terom@103:             return None
terom@103: 
terom@103:         # data format
terom@103:         if len(tag.type_format) == 1 :
terom@103:             # let struct handle the count
terom@103:             fmt = "%d%s" % (tag.count, tag.type_format)
terom@103: 
terom@103:         else :
terom@103:             # handle the count ourselves
terom@103:             fmt = tag.type_format * tag.count
terom@103: 
terom@103:         # size of the data
terom@103:         size = self.item_size(fmt)
terom@103: 
terom@103:         # inline or external?
terom@103:         if size > 0x04 :
terom@103:             # point at the external data
terom@103:             offset = self.unpack_item('I', tag.data_raw)
terom@103: 
terom@103:         else :
terom@103:             # point at the inline data
terom@103:             offset = tag.offset + 0x08
terom@103:         
terom@103:         return fmt, offset, size
terom@103: 
terom@103:     def tag_values_raw (self, tag) :
terom@102:         """
terom@102:             Get the raw values for the given tag as a tuple.
terom@102: 
terom@102:             Returns None if the tag could not be recognized.
terom@102:         """
terom@102: 
terom@103:         # find the data
terom@103:         data_info = self.tag_data_info(tag)
terom@102: 
terom@103:         # not found?
terom@103:         if not data_info :
terom@103:             return None
terom@103:         
terom@103:         # unpack
terom@103:         data_fmt, data_offset, data_size = data_info
terom@102:         
terom@102:         # read values
terom@103:         return self.pread_struct(data_offset, data_fmt)
terom@102:     
terom@103:     def tag_values (self, tag) :
terom@103:         """
terom@103:             Gets the processed values for the given tag as a list.
terom@103:         """
terom@103: 
terom@103:         # read + process
terom@103:         return tag.process_values(self.tag_values_raw(tag))
terom@103: 
terom@102:     def tag_value (self, tag) :
terom@102:         """
terom@102:             Return the human-readable string value for the given tag.
terom@102:         """
terom@102:         
terom@102:         # load the raw values
terom@102:         values = self.tag_values(tag)
terom@102: 
terom@102:         # unknown?
terom@102:         if not values :
terom@102:             return ""
terom@102: 
terom@102:         # return as comma-separated formatted string, yes
terom@104:         return tag.readable_value(values)
terom@102: 
terom@102: # mapping from two-byte TIFF byte order marker to struct prefix
terom@102: TIFF_BYTE_ORDER = {
terom@102:     'II': '<',
terom@102:     'MM': '>',
terom@102: }
terom@102: 
terom@102: # "An arbitrary but carefully chosen number (42) that further identifies the file as a TIFF file"
terom@102: TIFF_BYTEORDER_MAGIC = 42 
terom@102: 
terom@102: def tiff_load (file, length=0, **opts) :
terom@102:     """
terom@102:         Load the Exif/TIFF data from the given file at its current position with optional length, using exif_load.
terom@102:     """
terom@102: 
terom@102:     # all Exif data offsets are relative to the beginning of this TIFF header
terom@102:     offset = file.tell()
terom@102: 
terom@102:     # mmap the region for the EXIF data
terom@103:     buffer = mmap_buffer(file, length)
terom@102: 
terom@102:     # read byte-order header
terom@102:     byte_order = file.read(2)
terom@102: 
terom@102:     # map to struct prefix
terom@102:     struct_prefix = TIFF_BYTE_ORDER[byte_order]
terom@102: 
terom@102:     # validate
terom@102:     check_value, = read_struct(file, struct_prefix + 'H')
terom@102: 
terom@102:     if check_value != TIFF_BYTEORDER_MAGIC  :
terom@102:         raise Exception("Invalid byte-order for TIFF: %2c -> %d" % (byte_order, check_value))
terom@102: 
terom@102:     # build and return the EXIF object with the correct offset/size from the mmap region
terom@102:     return EXIF(buffer, offset=offset, size=length, **opts)
terom@102: 
terom@102: # the JPEG markers that don't have any data
terom@102: JPEG_NOSIZE_MARKERS = (0xD8, 0xD9)
terom@102: 
terom@102: # the first marker in a JPEG File
terom@102: JPEG_START_MARKER = 0xD8
terom@102: 
terom@102: # the JPEG APP1 marker used for EXIF
terom@102: JPEG_EXIF_MARKER = 0xE1
terom@102: 
terom@102: # the JPEG APP1 Exif header
terom@102: JPEG_EXIF_HEADER = "Exif\x00\x00"
terom@102: 
terom@102: def jpeg_markers (file) :
terom@102:     """
terom@102:         Iterate over the JPEG markers in the given file, yielding (type_byte, size) tuples.
terom@102: 
terom@102:         The size fields will be 0 for markers with no data. The file will be positioned at the beginning of the data
terom@102:         region, and may be seek'd around if needed.
terom@102:         
terom@102:         XXX: find a real implementation of this somewhere?
terom@102:     """
terom@102: 
terom@102:     while True :
terom@102:         # read type
terom@102:         marker_byte, marker_type = read_struct(file, '!BB')
terom@102:         
terom@102:         # validate
terom@102:         if marker_byte != 0xff :
terom@102:             raise Exception("Not a JPEG marker: %x%x" % (marker_byte, marker_type))
terom@102: 
terom@102:         # special cases for no data
terom@103:         if marker_type in JPEG_NOSIZE_MARKERS :
terom@102:             size = 0
terom@102: 
terom@102:         else :
terom@102:             # read size field
terom@102:             size, = read_struct(file, '!H')
terom@102:             
terom@102:             # validate
terom@102:             if size < 0x02 :
terom@102:                 raise Exception("Invalid size for marker %x%x: %x" % (marker_byte, marker_type, size))
terom@102:             
terom@102:             else :
terom@102:                 # do not count the size field itself
terom@102:                 size = size - 2
terom@102:             
terom@102:         # ok, data is at current position
terom@102:         offset = file.tell()
terom@102:         
terom@102:         # yield
terom@102:         yield marker_type, size
terom@102: 
terom@102:         # absolute seek to next marker
terom@102:         file.seek(offset + size)
terom@102: 
terom@102: def jpeg_find_exif (file) :
terom@102:     """
terom@102:         Find the Exif/TIFF section in the given JPEG file.
terom@102: 
terom@102:         If found, the file will be seek'd to the start of the Exif/TIFF header, and the size of the Exif/TIFF data will
terom@102:         be returned.
terom@102:         
terom@102:         Returns None if no EXIF section was found.
terom@102:     """
terom@102: 
terom@102:     for count, (marker, size) in enumerate(jpeg_markers(file)) :
terom@102:         # verify that it's a JPEG file
terom@102:         if count == 0 :
terom@102:             # must start with the right marker
terom@102:             if marker != JPEG_START_MARKER :
terom@102:                 raise Exception("JPEG file must start with 0xFF%02x marker" % (marker, ))
terom@102: 
terom@102:         # look for APP1 marker (0xE1) with EXIF signature
terom@102:         elif marker == JPEG_EXIF_MARKER and file.read(len(JPEG_EXIF_HEADER)) == JPEG_EXIF_HEADER:
terom@102:             # skipped the initial Exif marker signature
terom@103:             return size - len(JPEG_EXIF_HEADER)
terom@102: 
terom@102:     # nothing
terom@102:     return None
terom@102: 
terom@102: def jpeg_load (file, **opts) :
terom@102:     """
terom@102:         Loads the embedded Exif TIFF data from the given JPEG file using tiff_load.
terom@102: 
terom@102:         Returns None if no EXIF data could be found.
terom@102:     """
terom@102:         
terom@102:     # look for the right section
terom@102:     size = jpeg_find_exif(file)
terom@102:     
terom@102:     # not found?
terom@103:     if not size :
terom@102:         # nothing
terom@102:         return
terom@102: 
terom@102:     else :    
terom@102:         # load it as TIFF data
terom@102:         return tiff_load(file, size, **opts)
terom@102: 
terom@102: def load_path (path, **opts) :
terom@102:     """
terom@102:         Loads an EXIF object from the given filesystem path.
terom@102: 
terom@102:         Returns None if it could not be parsed.
terom@102:     """
terom@102:     
terom@102:     # file extension
terom@102:     root, fext = os.path.splitext(path)
terom@102: 
terom@102:     # map
terom@102:     func = {
terom@102:         '.jpeg':    jpeg_load,
terom@102:         '.jpg':     jpeg_load,
terom@102:         '.tiff':    tiff_load,  # XXX: untested
terom@102:     }.get(fext.lower())
terom@102:     
terom@102:     # not recognized?
terom@102:     if not func :
terom@102:         # XXX: sniff the file
terom@102:         return None
terom@102: 
terom@102:     # open it
terom@102:     file = open(path, 'rb')
terom@102: 
terom@102:     # try and load it
terom@102:     return func(file, **opts)
terom@102: 
terom@102: def dump_exif (exif) :
terom@102:     """
terom@102:         Dump all tags from the given EXIF object to stdout
terom@102:     """
terom@102: 
terom@103:     print "EXIF offset=%#08x, size=%d:" % (exif.offset, exif.size)
terom@102: 
terom@102:     for i, ifd in enumerate(exif.iter_ifds()) :
terom@103:         print "\tIFD:%d offset=%#04x(%#08x), count=%d, next=%d:" % (
terom@103:             i, 
terom@103:             ifd.offset, ifd.offset + exif.offset,
terom@103:             ifd.count, 
terom@103:             ifd.next_offset
terom@103:         )
terom@102:         
terom@103:         for i, tag in enumerate(ifd.iter_tags()) :
terom@103:             data_info = exif.tag_data_info(tag)
terom@103: 
terom@103:             if data_info :
terom@103:                 data_fmt, data_offset, data_size = data_info
terom@103: 
terom@103:             else :
terom@103:                 data_fmt = data_offset = data_size = None
terom@103: 
terom@103:             print "\t\tTag:%d offset=%#04x(%#08x), tag=%d/%s, type=%d/%s, count=%d, fmt=%s, offset=%#04x, size=%s:" % (
terom@102:                 i, 
terom@103:                 tag.offset, tag.offset + exif.offset,
terom@103:                 tag.tag, tag.name or '???',
terom@102:                 tag.type, tag.type_name if tag.type_data else '???',
terom@102:                 tag.count,
terom@103:                 data_fmt, data_offset, data_size,
terom@102:             )
terom@104: 
terom@104:             values = exif.tag_values(tag)
terom@102:             
terom@104:             for i, value in enumerate(values) :
terom@104:                 print "\t\t\t%02d: %r" % (i, value)
terom@102: 
terom@104:             print "\t\t\t->  %s" % (tag.readable_value(values), )
terom@104: 
terom@104: def main (path, quiet=False) :
terom@102:     """
terom@102:         Load and dump EXIF data from the given path
terom@102:     """
terom@102:     
terom@102:     # try and load it
terom@102:     exif = load_path(path)
terom@102: 
terom@102:     if not exif :
terom@102:         raise Exception("No EXIF data found")
terom@102:     
terom@104:     if not quiet :
terom@104:         # dump it
terom@104:         print "%s: " % path
terom@104:         print
terom@102: 
terom@104:         dump_exif(exif)
terom@102: 
terom@102: if __name__ == '__main__' :
terom@102:     from sys import argv
terom@102: 
terom@104:     main(argv[1], '-q' in argv)
terom@102: