JPEG File Interchange Format, or JFIF, or, more colloquially known as just "JPEG" or "JPG", is a popular 2D bitmap image file format, offering lossy compression which works reasonably well with photographic images.
Format is organized as a container format, serving multiple "segments", each starting with a magic and a marker. JFIF standard dictates order and mandatory apperance of segments:
This page hosts a formal specification of JPEG (Joint Photographic Experts Group) File Interchange Format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = Jpeg.from_file("path/to/local/file.jpg")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = Jpeg(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.segments # => get segments
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
import exif
class Jpeg(KaitaiStruct):
"""JPEG File Interchange Format, or JFIF, or, more colloquially known
as just "JPEG" or "JPG", is a popular 2D bitmap image file format,
offering lossy compression which works reasonably well with
photographic images.
Format is organized as a container format, serving multiple
"segments", each starting with a magic and a marker. JFIF standard
dictates order and mandatory apperance of segments:
* SOI
* APP0 (with JFIF magic)
* APP0 (with JFXX magic, optional)
* everything else
* SOS
* JPEG-compressed stream
* EOI
"""
class ComponentId(Enum):
y = 1
cb = 2
cr = 3
i = 4
q = 5
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.segments = []
i = 0
while not self._io.is_eof():
self.segments.append(Jpeg.Segment(self._io, self, self._root))
i += 1
class Segment(KaitaiStruct):
class MarkerEnum(Enum):
tem = 1
sof0 = 192
sof1 = 193
sof2 = 194
sof3 = 195
dht = 196
sof5 = 197
sof6 = 198
sof7 = 199
soi = 216
eoi = 217
sos = 218
dqt = 219
dnl = 220
dri = 221
dhp = 222
app0 = 224
app1 = 225
app2 = 226
app3 = 227
app4 = 228
app5 = 229
app6 = 230
app7 = 231
app8 = 232
app9 = 233
app10 = 234
app11 = 235
app12 = 236
app13 = 237
app14 = 238
app15 = 239
com = 254
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.magic = self._io.read_bytes(1)
if not self.magic == b"\xFF":
raise kaitaistruct.ValidationNotEqualError(b"\xFF", self.magic, self._io, u"/types/segment/seq/0")
self.marker = KaitaiStream.resolve_enum(Jpeg.Segment.MarkerEnum, self._io.read_u1())
if ((self.marker != Jpeg.Segment.MarkerEnum.soi) and (self.marker != Jpeg.Segment.MarkerEnum.eoi)) :
self.length = self._io.read_u2be()
if ((self.marker != Jpeg.Segment.MarkerEnum.soi) and (self.marker != Jpeg.Segment.MarkerEnum.eoi)) :
_on = self.marker
if _on == Jpeg.Segment.MarkerEnum.app1:
self._raw_data = self._io.read_bytes((self.length - 2))
_io__raw_data = KaitaiStream(BytesIO(self._raw_data))
self.data = Jpeg.SegmentApp1(_io__raw_data, self, self._root)
elif _on == Jpeg.Segment.MarkerEnum.app0:
self._raw_data = self._io.read_bytes((self.length - 2))
_io__raw_data = KaitaiStream(BytesIO(self._raw_data))
self.data = Jpeg.SegmentApp0(_io__raw_data, self, self._root)
elif _on == Jpeg.Segment.MarkerEnum.sof0:
self._raw_data = self._io.read_bytes((self.length - 2))
_io__raw_data = KaitaiStream(BytesIO(self._raw_data))
self.data = Jpeg.SegmentSof0(_io__raw_data, self, self._root)
elif _on == Jpeg.Segment.MarkerEnum.sos:
self._raw_data = self._io.read_bytes((self.length - 2))
_io__raw_data = KaitaiStream(BytesIO(self._raw_data))
self.data = Jpeg.SegmentSos(_io__raw_data, self, self._root)
else:
self.data = self._io.read_bytes((self.length - 2))
if self.marker == Jpeg.Segment.MarkerEnum.sos:
self.image_data = self._io.read_bytes_full()
class SegmentSos(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.num_components = self._io.read_u1()
self.components = []
for i in range(self.num_components):
self.components.append(Jpeg.SegmentSos.Component(self._io, self, self._root))
self.start_spectral_selection = self._io.read_u1()
self.end_spectral = self._io.read_u1()
self.appr_bit_pos = self._io.read_u1()
class Component(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.id = KaitaiStream.resolve_enum(Jpeg.ComponentId, self._io.read_u1())
self.huffman_table = self._io.read_u1()
class SegmentApp1(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.magic = (self._io.read_bytes_term(0, False, True, True)).decode(u"ASCII")
_on = self.magic
if _on == u"Exif":
self.body = Jpeg.ExifInJpeg(self._io, self, self._root)
class SegmentSof0(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.bits_per_sample = self._io.read_u1()
self.image_height = self._io.read_u2be()
self.image_width = self._io.read_u2be()
self.num_components = self._io.read_u1()
self.components = []
for i in range(self.num_components):
self.components.append(Jpeg.SegmentSof0.Component(self._io, self, self._root))
class Component(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.id = KaitaiStream.resolve_enum(Jpeg.ComponentId, self._io.read_u1())
self.sampling_factors = self._io.read_u1()
self.quantization_table_id = self._io.read_u1()
@property
def sampling_x(self):
if hasattr(self, '_m_sampling_x'):
return self._m_sampling_x
self._m_sampling_x = ((self.sampling_factors & 240) >> 4)
return getattr(self, '_m_sampling_x', None)
@property
def sampling_y(self):
if hasattr(self, '_m_sampling_y'):
return self._m_sampling_y
self._m_sampling_y = (self.sampling_factors & 15)
return getattr(self, '_m_sampling_y', None)
class ExifInJpeg(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.extra_zero = self._io.read_bytes(1)
if not self.extra_zero == b"\x00":
raise kaitaistruct.ValidationNotEqualError(b"\x00", self.extra_zero, self._io, u"/types/exif_in_jpeg/seq/0")
self._raw_data = self._io.read_bytes_full()
_io__raw_data = KaitaiStream(BytesIO(self._raw_data))
self.data = exif.Exif(_io__raw_data)
class SegmentApp0(KaitaiStruct):
class DensityUnit(Enum):
no_units = 0
pixels_per_inch = 1
pixels_per_cm = 2
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.magic = (self._io.read_bytes(5)).decode(u"ASCII")
self.version_major = self._io.read_u1()
self.version_minor = self._io.read_u1()
self.density_units = KaitaiStream.resolve_enum(Jpeg.SegmentApp0.DensityUnit, self._io.read_u1())
self.density_x = self._io.read_u2be()
self.density_y = self._io.read_u2be()
self.thumbnail_x = self._io.read_u1()
self.thumbnail_y = self._io.read_u1()
self.thumbnail = self._io.read_bytes(((self.thumbnail_x * self.thumbnail_y) * 3))