GIF (Graphics Interchange Format) is an image file format, developed in 1987. It became popular in 1990s as one of the main image formats used in World Wide Web.
GIF format allows encoding of palette-based images up to 256 colors (each of the colors can be chosen from a 24-bit RGB colorspace). Image data stream uses LZW (Lempel-Ziv-Welch) lossless compression.
Over the years, several version of the format were published and several extensions to it were made, namely, a popular Netscape extension that allows to store several images in one file, switching between them, which produces crude form of animation.
Structurally, format consists of several mandatory headers and then a stream of blocks follows. Blocks can carry additional metainformation or image data.
This page hosts a formal specification of GIF (Graphics Interchange Format) image file using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
# type: ignore
import kaitaistruct
from kaitaistruct import ReadWriteKaitaiStruct, KaitaiStream, BytesIO
from enum import IntEnum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 11):
raise Exception("Incompatible Kaitai Struct Python API: 0.11 or later is required, but you have %s" % (kaitaistruct.__version__))
class Gif(ReadWriteKaitaiStruct):
"""GIF (Graphics Interchange Format) is an image file format, developed
in 1987. It became popular in 1990s as one of the main image formats
used in World Wide Web.
GIF format allows encoding of palette-based images up to 256 colors
(each of the colors can be chosen from a 24-bit RGB
colorspace). Image data stream uses LZW (Lempel-Ziv-Welch) lossless
compression.
Over the years, several version of the format were published and
several extensions to it were made, namely, a popular Netscape
extension that allows to store several images in one file, switching
between them, which produces crude form of animation.
Structurally, format consists of several mandatory headers and then
a stream of blocks follows. Blocks can carry additional
metainformation or image data.
"""
class BlockType(IntEnum):
extension = 33
local_image_descriptor = 44
end_of_file = 59
class ExtensionLabel(IntEnum):
graphic_control = 249
comment = 254
application = 255
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif, self).__init__(_io)
self._parent = _parent
self._root = _root or self
def _read(self):
self.hdr = Gif.Header(self._io, self, self._root)
self.hdr._read()
self.logical_screen_descriptor = Gif.LogicalScreenDescriptorStruct(self._io, self, self._root)
self.logical_screen_descriptor._read()
if self.logical_screen_descriptor.has_color_table:
pass
self._raw_global_color_table = self._io.read_bytes(self.logical_screen_descriptor.color_table_size * 3)
_io__raw_global_color_table = KaitaiStream(BytesIO(self._raw_global_color_table))
self.global_color_table = Gif.ColorTable(_io__raw_global_color_table, self, self._root)
self.global_color_table._read()
self.blocks = []
i = 0
while True:
_t_blocks = Gif.Block(self._io, self, self._root)
try:
_t_blocks._read()
finally:
_ = _t_blocks
self.blocks.append(_)
if ((self._io.is_eof()) or (_.block_type == Gif.BlockType.end_of_file)) :
break
i += 1
self._dirty = False
def _fetch_instances(self):
pass
self.hdr._fetch_instances()
self.logical_screen_descriptor._fetch_instances()
if self.logical_screen_descriptor.has_color_table:
pass
self.global_color_table._fetch_instances()
for i in range(len(self.blocks)):
pass
self.blocks[i]._fetch_instances()
def _write__seq(self, io=None):
super(Gif, self)._write__seq(io)
self.hdr._write__seq(self._io)
self.logical_screen_descriptor._write__seq(self._io)
if self.logical_screen_descriptor.has_color_table:
pass
_io__raw_global_color_table = KaitaiStream(BytesIO(bytearray(self.logical_screen_descriptor.color_table_size * 3)))
self._io.add_child_stream(_io__raw_global_color_table)
_pos2 = self._io.pos()
self._io.seek(self._io.pos() + (self.logical_screen_descriptor.color_table_size * 3))
def handler(parent, _io__raw_global_color_table=_io__raw_global_color_table):
self._raw_global_color_table = _io__raw_global_color_table.to_byte_array()
if len(self._raw_global_color_table) != self.logical_screen_descriptor.color_table_size * 3:
raise kaitaistruct.ConsistencyError(u"raw(global_color_table)", self.logical_screen_descriptor.color_table_size * 3, len(self._raw_global_color_table))
parent.write_bytes(self._raw_global_color_table)
_io__raw_global_color_table.write_back_handler = KaitaiStream.WriteBackHandler(_pos2, handler)
self.global_color_table._write__seq(_io__raw_global_color_table)
for i in range(len(self.blocks)):
pass
self.blocks[i]._write__seq(self._io)
_ = self.blocks[i]
if ((self._io.is_eof()) or (_.block_type == Gif.BlockType.end_of_file)) != (i == len(self.blocks) - 1):
raise kaitaistruct.ConsistencyError(u"blocks", i == len(self.blocks) - 1, ((self._io.is_eof()) or (_.block_type == Gif.BlockType.end_of_file)) )
def _check(self):
if self.hdr._root != self._root:
raise kaitaistruct.ConsistencyError(u"hdr", self._root, self.hdr._root)
if self.hdr._parent != self:
raise kaitaistruct.ConsistencyError(u"hdr", self, self.hdr._parent)
if self.logical_screen_descriptor._root != self._root:
raise kaitaistruct.ConsistencyError(u"logical_screen_descriptor", self._root, self.logical_screen_descriptor._root)
if self.logical_screen_descriptor._parent != self:
raise kaitaistruct.ConsistencyError(u"logical_screen_descriptor", self, self.logical_screen_descriptor._parent)
if self.logical_screen_descriptor.has_color_table:
pass
if self.global_color_table._root != self._root:
raise kaitaistruct.ConsistencyError(u"global_color_table", self._root, self.global_color_table._root)
if self.global_color_table._parent != self:
raise kaitaistruct.ConsistencyError(u"global_color_table", self, self.global_color_table._parent)
if len(self.blocks) == 0:
raise kaitaistruct.ConsistencyError(u"blocks", 0, len(self.blocks))
for i in range(len(self.blocks)):
pass
if self.blocks[i]._root != self._root:
raise kaitaistruct.ConsistencyError(u"blocks", self._root, self.blocks[i]._root)
if self.blocks[i]._parent != self:
raise kaitaistruct.ConsistencyError(u"blocks", self, self.blocks[i]._parent)
self._dirty = False
class ApplicationId(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.ApplicationId, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.len_bytes = self._io.read_u1()
if not self.len_bytes == 11:
raise kaitaistruct.ValidationNotEqualError(11, self.len_bytes, self._io, u"/types/application_id/seq/0")
self.application_identifier = (self._io.read_bytes(8)).decode(u"ASCII")
self.application_auth_code = self._io.read_bytes(3)
self._dirty = False
def _fetch_instances(self):
pass
def _write__seq(self, io=None):
super(Gif.ApplicationId, self)._write__seq(io)
self._io.write_u1(self.len_bytes)
self._io.write_bytes((self.application_identifier).encode(u"ASCII"))
self._io.write_bytes(self.application_auth_code)
def _check(self):
if not self.len_bytes == 11:
raise kaitaistruct.ValidationNotEqualError(11, self.len_bytes, None, u"/types/application_id/seq/0")
if len((self.application_identifier).encode(u"ASCII")) != 8:
raise kaitaistruct.ConsistencyError(u"application_identifier", 8, len((self.application_identifier).encode(u"ASCII")))
if len(self.application_auth_code) != 3:
raise kaitaistruct.ConsistencyError(u"application_auth_code", 3, len(self.application_auth_code))
self._dirty = False
class Block(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.Block, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.block_type = KaitaiStream.resolve_enum(Gif.BlockType, self._io.read_u1())
_on = self.block_type
if _on == Gif.BlockType.extension:
pass
self.body = Gif.Extension(self._io, self, self._root)
self.body._read()
elif _on == Gif.BlockType.local_image_descriptor:
pass
self.body = Gif.LocalImageDescriptor(self._io, self, self._root)
self.body._read()
self._dirty = False
def _fetch_instances(self):
pass
_on = self.block_type
if _on == Gif.BlockType.extension:
pass
self.body._fetch_instances()
elif _on == Gif.BlockType.local_image_descriptor:
pass
self.body._fetch_instances()
def _write__seq(self, io=None):
super(Gif.Block, self)._write__seq(io)
self._io.write_u1(int(self.block_type))
_on = self.block_type
if _on == Gif.BlockType.extension:
pass
self.body._write__seq(self._io)
elif _on == Gif.BlockType.local_image_descriptor:
pass
self.body._write__seq(self._io)
def _check(self):
_on = self.block_type
if _on == Gif.BlockType.extension:
pass
if self.body._root != self._root:
raise kaitaistruct.ConsistencyError(u"body", self._root, self.body._root)
if self.body._parent != self:
raise kaitaistruct.ConsistencyError(u"body", self, self.body._parent)
elif _on == Gif.BlockType.local_image_descriptor:
pass
if self.body._root != self._root:
raise kaitaistruct.ConsistencyError(u"body", self._root, self.body._root)
if self.body._parent != self:
raise kaitaistruct.ConsistencyError(u"body", self, self.body._parent)
self._dirty = False
class ColorTable(ReadWriteKaitaiStruct):
"""
.. seealso::
- section 19 - https://www.w3.org/Graphics/GIF/spec-gif89a.txt
"""
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.ColorTable, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.entries = []
i = 0
while not self._io.is_eof():
_t_entries = Gif.ColorTableEntry(self._io, self, self._root)
try:
_t_entries._read()
finally:
self.entries.append(_t_entries)
i += 1
self._dirty = False
def _fetch_instances(self):
pass
for i in range(len(self.entries)):
pass
self.entries[i]._fetch_instances()
def _write__seq(self, io=None):
super(Gif.ColorTable, self)._write__seq(io)
for i in range(len(self.entries)):
pass
if self._io.is_eof():
raise kaitaistruct.ConsistencyError(u"entries", 0, self._io.size() - self._io.pos())
self.entries[i]._write__seq(self._io)
if not self._io.is_eof():
raise kaitaistruct.ConsistencyError(u"entries", 0, self._io.size() - self._io.pos())
def _check(self):
for i in range(len(self.entries)):
pass
if self.entries[i]._root != self._root:
raise kaitaistruct.ConsistencyError(u"entries", self._root, self.entries[i]._root)
if self.entries[i]._parent != self:
raise kaitaistruct.ConsistencyError(u"entries", self, self.entries[i]._parent)
self._dirty = False
class ColorTableEntry(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.ColorTableEntry, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.red = self._io.read_u1()
self.green = self._io.read_u1()
self.blue = self._io.read_u1()
self._dirty = False
def _fetch_instances(self):
pass
def _write__seq(self, io=None):
super(Gif.ColorTableEntry, self)._write__seq(io)
self._io.write_u1(self.red)
self._io.write_u1(self.green)
self._io.write_u1(self.blue)
def _check(self):
self._dirty = False
class ExtApplication(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.ExtApplication, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.application_id = Gif.ApplicationId(self._io, self, self._root)
self.application_id._read()
self.subblocks = []
i = 0
while True:
_t_subblocks = Gif.Subblock(self._io, self, self._root)
try:
_t_subblocks._read()
finally:
_ = _t_subblocks
self.subblocks.append(_)
if _.len_bytes == 0:
break
i += 1
self._dirty = False
def _fetch_instances(self):
pass
self.application_id._fetch_instances()
for i in range(len(self.subblocks)):
pass
self.subblocks[i]._fetch_instances()
def _write__seq(self, io=None):
super(Gif.ExtApplication, self)._write__seq(io)
self.application_id._write__seq(self._io)
for i in range(len(self.subblocks)):
pass
self.subblocks[i]._write__seq(self._io)
def _check(self):
if self.application_id._root != self._root:
raise kaitaistruct.ConsistencyError(u"application_id", self._root, self.application_id._root)
if self.application_id._parent != self:
raise kaitaistruct.ConsistencyError(u"application_id", self, self.application_id._parent)
if len(self.subblocks) == 0:
raise kaitaistruct.ConsistencyError(u"subblocks", 0, len(self.subblocks))
for i in range(len(self.subblocks)):
pass
if self.subblocks[i]._root != self._root:
raise kaitaistruct.ConsistencyError(u"subblocks", self._root, self.subblocks[i]._root)
if self.subblocks[i]._parent != self:
raise kaitaistruct.ConsistencyError(u"subblocks", self, self.subblocks[i]._parent)
_ = self.subblocks[i]
if (_.len_bytes == 0) != (i == len(self.subblocks) - 1):
raise kaitaistruct.ConsistencyError(u"subblocks", i == len(self.subblocks) - 1, _.len_bytes == 0)
self._dirty = False
class ExtGraphicControl(ReadWriteKaitaiStruct):
"""
.. seealso::
- section 23 - https://www.w3.org/Graphics/GIF/spec-gif89a.txt
"""
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.ExtGraphicControl, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.block_size = self._io.read_bytes(1)
if not self.block_size == b"\x04":
raise kaitaistruct.ValidationNotEqualError(b"\x04", self.block_size, self._io, u"/types/ext_graphic_control/seq/0")
self.flags = self._io.read_u1()
self.delay_time = self._io.read_u2le()
self.transparent_idx = self._io.read_u1()
self.terminator = self._io.read_bytes(1)
if not self.terminator == b"\x00":
raise kaitaistruct.ValidationNotEqualError(b"\x00", self.terminator, self._io, u"/types/ext_graphic_control/seq/4")
self._dirty = False
def _fetch_instances(self):
pass
def _write__seq(self, io=None):
super(Gif.ExtGraphicControl, self)._write__seq(io)
self._io.write_bytes(self.block_size)
self._io.write_u1(self.flags)
self._io.write_u2le(self.delay_time)
self._io.write_u1(self.transparent_idx)
self._io.write_bytes(self.terminator)
def _check(self):
if len(self.block_size) != 1:
raise kaitaistruct.ConsistencyError(u"block_size", 1, len(self.block_size))
if not self.block_size == b"\x04":
raise kaitaistruct.ValidationNotEqualError(b"\x04", self.block_size, None, u"/types/ext_graphic_control/seq/0")
if len(self.terminator) != 1:
raise kaitaistruct.ConsistencyError(u"terminator", 1, len(self.terminator))
if not self.terminator == b"\x00":
raise kaitaistruct.ValidationNotEqualError(b"\x00", self.terminator, None, u"/types/ext_graphic_control/seq/4")
self._dirty = False
@property
def transparent_color_flag(self):
if hasattr(self, '_m_transparent_color_flag'):
return self._m_transparent_color_flag
self._m_transparent_color_flag = self.flags & 1 != 0
return getattr(self, '_m_transparent_color_flag', None)
def _invalidate_transparent_color_flag(self):
del self._m_transparent_color_flag
@property
def user_input_flag(self):
if hasattr(self, '_m_user_input_flag'):
return self._m_user_input_flag
self._m_user_input_flag = self.flags & 2 != 0
return getattr(self, '_m_user_input_flag', None)
def _invalidate_user_input_flag(self):
del self._m_user_input_flag
class Extension(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.Extension, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.label = KaitaiStream.resolve_enum(Gif.ExtensionLabel, self._io.read_u1())
_on = self.label
if _on == Gif.ExtensionLabel.application:
pass
self.body = Gif.ExtApplication(self._io, self, self._root)
self.body._read()
elif _on == Gif.ExtensionLabel.comment:
pass
self.body = Gif.Subblocks(self._io, self, self._root)
self.body._read()
elif _on == Gif.ExtensionLabel.graphic_control:
pass
self.body = Gif.ExtGraphicControl(self._io, self, self._root)
self.body._read()
else:
pass
self.body = Gif.Subblocks(self._io, self, self._root)
self.body._read()
self._dirty = False
def _fetch_instances(self):
pass
_on = self.label
if _on == Gif.ExtensionLabel.application:
pass
self.body._fetch_instances()
elif _on == Gif.ExtensionLabel.comment:
pass
self.body._fetch_instances()
elif _on == Gif.ExtensionLabel.graphic_control:
pass
self.body._fetch_instances()
else:
pass
self.body._fetch_instances()
def _write__seq(self, io=None):
super(Gif.Extension, self)._write__seq(io)
self._io.write_u1(int(self.label))
_on = self.label
if _on == Gif.ExtensionLabel.application:
pass
self.body._write__seq(self._io)
elif _on == Gif.ExtensionLabel.comment:
pass
self.body._write__seq(self._io)
elif _on == Gif.ExtensionLabel.graphic_control:
pass
self.body._write__seq(self._io)
else:
pass
self.body._write__seq(self._io)
def _check(self):
_on = self.label
if _on == Gif.ExtensionLabel.application:
pass
if self.body._root != self._root:
raise kaitaistruct.ConsistencyError(u"body", self._root, self.body._root)
if self.body._parent != self:
raise kaitaistruct.ConsistencyError(u"body", self, self.body._parent)
elif _on == Gif.ExtensionLabel.comment:
pass
if self.body._root != self._root:
raise kaitaistruct.ConsistencyError(u"body", self._root, self.body._root)
if self.body._parent != self:
raise kaitaistruct.ConsistencyError(u"body", self, self.body._parent)
elif _on == Gif.ExtensionLabel.graphic_control:
pass
if self.body._root != self._root:
raise kaitaistruct.ConsistencyError(u"body", self._root, self.body._root)
if self.body._parent != self:
raise kaitaistruct.ConsistencyError(u"body", self, self.body._parent)
else:
pass
if self.body._root != self._root:
raise kaitaistruct.ConsistencyError(u"body", self._root, self.body._root)
if self.body._parent != self:
raise kaitaistruct.ConsistencyError(u"body", self, self.body._parent)
self._dirty = False
class Header(ReadWriteKaitaiStruct):
"""
.. seealso::
- section 17 - https://www.w3.org/Graphics/GIF/spec-gif89a.txt
"""
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.Header, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.magic = self._io.read_bytes(3)
if not self.magic == b"\x47\x49\x46":
raise kaitaistruct.ValidationNotEqualError(b"\x47\x49\x46", self.magic, self._io, u"/types/header/seq/0")
self.version = (self._io.read_bytes(3)).decode(u"ASCII")
self._dirty = False
def _fetch_instances(self):
pass
def _write__seq(self, io=None):
super(Gif.Header, self)._write__seq(io)
self._io.write_bytes(self.magic)
self._io.write_bytes((self.version).encode(u"ASCII"))
def _check(self):
if len(self.magic) != 3:
raise kaitaistruct.ConsistencyError(u"magic", 3, len(self.magic))
if not self.magic == b"\x47\x49\x46":
raise kaitaistruct.ValidationNotEqualError(b"\x47\x49\x46", self.magic, None, u"/types/header/seq/0")
if len((self.version).encode(u"ASCII")) != 3:
raise kaitaistruct.ConsistencyError(u"version", 3, len((self.version).encode(u"ASCII")))
self._dirty = False
class ImageData(ReadWriteKaitaiStruct):
"""
.. seealso::
- section 22 - https://www.w3.org/Graphics/GIF/spec-gif89a.txt
"""
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.ImageData, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.lzw_min_code_size = self._io.read_u1()
self.subblocks = Gif.Subblocks(self._io, self, self._root)
self.subblocks._read()
self._dirty = False
def _fetch_instances(self):
pass
self.subblocks._fetch_instances()
def _write__seq(self, io=None):
super(Gif.ImageData, self)._write__seq(io)
self._io.write_u1(self.lzw_min_code_size)
self.subblocks._write__seq(self._io)
def _check(self):
if self.subblocks._root != self._root:
raise kaitaistruct.ConsistencyError(u"subblocks", self._root, self.subblocks._root)
if self.subblocks._parent != self:
raise kaitaistruct.ConsistencyError(u"subblocks", self, self.subblocks._parent)
self._dirty = False
class LocalImageDescriptor(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.LocalImageDescriptor, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.left = self._io.read_u2le()
self.top = self._io.read_u2le()
self.width = self._io.read_u2le()
self.height = self._io.read_u2le()
self.flags = self._io.read_u1()
if self.has_color_table:
pass
self._raw_local_color_table = self._io.read_bytes(self.color_table_size * 3)
_io__raw_local_color_table = KaitaiStream(BytesIO(self._raw_local_color_table))
self.local_color_table = Gif.ColorTable(_io__raw_local_color_table, self, self._root)
self.local_color_table._read()
self.image_data = Gif.ImageData(self._io, self, self._root)
self.image_data._read()
self._dirty = False
def _fetch_instances(self):
pass
if self.has_color_table:
pass
self.local_color_table._fetch_instances()
self.image_data._fetch_instances()
def _write__seq(self, io=None):
super(Gif.LocalImageDescriptor, self)._write__seq(io)
self._io.write_u2le(self.left)
self._io.write_u2le(self.top)
self._io.write_u2le(self.width)
self._io.write_u2le(self.height)
self._io.write_u1(self.flags)
if self.has_color_table:
pass
_io__raw_local_color_table = KaitaiStream(BytesIO(bytearray(self.color_table_size * 3)))
self._io.add_child_stream(_io__raw_local_color_table)
_pos2 = self._io.pos()
self._io.seek(self._io.pos() + (self.color_table_size * 3))
def handler(parent, _io__raw_local_color_table=_io__raw_local_color_table):
self._raw_local_color_table = _io__raw_local_color_table.to_byte_array()
if len(self._raw_local_color_table) != self.color_table_size * 3:
raise kaitaistruct.ConsistencyError(u"raw(local_color_table)", self.color_table_size * 3, len(self._raw_local_color_table))
parent.write_bytes(self._raw_local_color_table)
_io__raw_local_color_table.write_back_handler = KaitaiStream.WriteBackHandler(_pos2, handler)
self.local_color_table._write__seq(_io__raw_local_color_table)
self.image_data._write__seq(self._io)
def _check(self):
if self.has_color_table:
pass
if self.local_color_table._root != self._root:
raise kaitaistruct.ConsistencyError(u"local_color_table", self._root, self.local_color_table._root)
if self.local_color_table._parent != self:
raise kaitaistruct.ConsistencyError(u"local_color_table", self, self.local_color_table._parent)
if self.image_data._root != self._root:
raise kaitaistruct.ConsistencyError(u"image_data", self._root, self.image_data._root)
if self.image_data._parent != self:
raise kaitaistruct.ConsistencyError(u"image_data", self, self.image_data._parent)
self._dirty = False
@property
def color_table_size(self):
if hasattr(self, '_m_color_table_size'):
return self._m_color_table_size
self._m_color_table_size = 2 << (self.flags & 7)
return getattr(self, '_m_color_table_size', None)
def _invalidate_color_table_size(self):
del self._m_color_table_size
@property
def has_color_table(self):
if hasattr(self, '_m_has_color_table'):
return self._m_has_color_table
self._m_has_color_table = self.flags & 128 != 0
return getattr(self, '_m_has_color_table', None)
def _invalidate_has_color_table(self):
del self._m_has_color_table
@property
def has_interlace(self):
if hasattr(self, '_m_has_interlace'):
return self._m_has_interlace
self._m_has_interlace = self.flags & 64 != 0
return getattr(self, '_m_has_interlace', None)
def _invalidate_has_interlace(self):
del self._m_has_interlace
@property
def has_sorted_color_table(self):
if hasattr(self, '_m_has_sorted_color_table'):
return self._m_has_sorted_color_table
self._m_has_sorted_color_table = self.flags & 32 != 0
return getattr(self, '_m_has_sorted_color_table', None)
def _invalidate_has_sorted_color_table(self):
del self._m_has_sorted_color_table
class LogicalScreenDescriptorStruct(ReadWriteKaitaiStruct):
"""
.. seealso::
- section 18 - https://www.w3.org/Graphics/GIF/spec-gif89a.txt
"""
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.LogicalScreenDescriptorStruct, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.screen_width = self._io.read_u2le()
self.screen_height = self._io.read_u2le()
self.flags = self._io.read_u1()
self.bg_color_index = self._io.read_u1()
self.pixel_aspect_ratio = self._io.read_u1()
self._dirty = False
def _fetch_instances(self):
pass
def _write__seq(self, io=None):
super(Gif.LogicalScreenDescriptorStruct, self)._write__seq(io)
self._io.write_u2le(self.screen_width)
self._io.write_u2le(self.screen_height)
self._io.write_u1(self.flags)
self._io.write_u1(self.bg_color_index)
self._io.write_u1(self.pixel_aspect_ratio)
def _check(self):
self._dirty = False
@property
def color_table_size(self):
if hasattr(self, '_m_color_table_size'):
return self._m_color_table_size
self._m_color_table_size = 2 << (self.flags & 7)
return getattr(self, '_m_color_table_size', None)
def _invalidate_color_table_size(self):
del self._m_color_table_size
@property
def has_color_table(self):
if hasattr(self, '_m_has_color_table'):
return self._m_has_color_table
self._m_has_color_table = self.flags & 128 != 0
return getattr(self, '_m_has_color_table', None)
def _invalidate_has_color_table(self):
del self._m_has_color_table
class Subblock(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.Subblock, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.len_bytes = self._io.read_u1()
self.bytes = self._io.read_bytes(self.len_bytes)
self._dirty = False
def _fetch_instances(self):
pass
def _write__seq(self, io=None):
super(Gif.Subblock, self)._write__seq(io)
self._io.write_u1(self.len_bytes)
self._io.write_bytes(self.bytes)
def _check(self):
if len(self.bytes) != self.len_bytes:
raise kaitaistruct.ConsistencyError(u"bytes", self.len_bytes, len(self.bytes))
self._dirty = False
class Subblocks(ReadWriteKaitaiStruct):
def __init__(self, _io=None, _parent=None, _root=None):
super(Gif.Subblocks, self).__init__(_io)
self._parent = _parent
self._root = _root
def _read(self):
self.entries = []
i = 0
while True:
_t_entries = Gif.Subblock(self._io, self, self._root)
try:
_t_entries._read()
finally:
_ = _t_entries
self.entries.append(_)
if _.len_bytes == 0:
break
i += 1
self._dirty = False
def _fetch_instances(self):
pass
for i in range(len(self.entries)):
pass
self.entries[i]._fetch_instances()
def _write__seq(self, io=None):
super(Gif.Subblocks, self)._write__seq(io)
for i in range(len(self.entries)):
pass
self.entries[i]._write__seq(self._io)
def _check(self):
if len(self.entries) == 0:
raise kaitaistruct.ConsistencyError(u"entries", 0, len(self.entries))
for i in range(len(self.entries)):
pass
if self.entries[i]._root != self._root:
raise kaitaistruct.ConsistencyError(u"entries", self._root, self.entries[i]._root)
if self.entries[i]._parent != self:
raise kaitaistruct.ConsistencyError(u"entries", self, self.entries[i]._parent)
_ = self.entries[i]
if (_.len_bytes == 0) != (i == len(self.entries) - 1):
raise kaitaistruct.ConsistencyError(u"entries", i == len(self.entries) - 1, _.len_bytes == 0)
self._dirty = False