Test files for APNG can be found at the following locations:
This page hosts a formal specification of PNG (Portable Network Graphics) file 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 = Png.from_file("path/to/local/file.png")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = Png(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.magic # => get magic
# 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
import zlib
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__))
class Png(KaitaiStruct):
"""Test files for APNG can be found at the following locations:
* <https://philip.html5.org/tests/apng/tests.html>
* <http://littlesvr.ca/apng/>
"""
class PhysUnit(Enum):
unknown = 0
meter = 1
class BlendOpValues(Enum):
source = 0
over = 1
class CompressionMethods(Enum):
zlib = 0
class DisposeOpValues(Enum):
none = 0
background = 1
previous = 2
class ColorType(Enum):
greyscale = 0
truecolor = 2
indexed = 3
greyscale_alpha = 4
truecolor_alpha = 6
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(8)
if not self.magic == b"\x89\x50\x4E\x47\x0D\x0A\x1A\x0A":
raise kaitaistruct.ValidationNotEqualError(b"\x89\x50\x4E\x47\x0D\x0A\x1A\x0A", self.magic, self._io, u"/seq/0")
self.ihdr_len = self._io.read_u4be()
if not self.ihdr_len == 13:
raise kaitaistruct.ValidationNotEqualError(13, self.ihdr_len, self._io, u"/seq/1")
self.ihdr_type = self._io.read_bytes(4)
if not self.ihdr_type == b"\x49\x48\x44\x52":
raise kaitaistruct.ValidationNotEqualError(b"\x49\x48\x44\x52", self.ihdr_type, self._io, u"/seq/2")
self.ihdr = Png.IhdrChunk(self._io, self, self._root)
self.ihdr_crc = self._io.read_bytes(4)
self.chunks = []
i = 0
while True:
_ = Png.Chunk(self._io, self, self._root)
self.chunks.append(_)
if ((_.type == u"IEND") or (self._io.is_eof())) :
break
i += 1
class Rgb(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.r = self._io.read_u1()
self.g = self._io.read_u1()
self.b = self._io.read_u1()
class Chunk(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.len = self._io.read_u4be()
self.type = (self._io.read_bytes(4)).decode(u"UTF-8")
_on = self.type
if _on == u"iTXt":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.InternationalTextChunk(_io__raw_body, self, self._root)
elif _on == u"gAMA":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.GamaChunk(_io__raw_body, self, self._root)
elif _on == u"tIME":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.TimeChunk(_io__raw_body, self, self._root)
elif _on == u"PLTE":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.PlteChunk(_io__raw_body, self, self._root)
elif _on == u"bKGD":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.BkgdChunk(_io__raw_body, self, self._root)
elif _on == u"pHYs":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.PhysChunk(_io__raw_body, self, self._root)
elif _on == u"fdAT":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.FrameDataChunk(_io__raw_body, self, self._root)
elif _on == u"tEXt":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.TextChunk(_io__raw_body, self, self._root)
elif _on == u"cHRM":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.ChrmChunk(_io__raw_body, self, self._root)
elif _on == u"acTL":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.AnimationControlChunk(_io__raw_body, self, self._root)
elif _on == u"sRGB":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.SrgbChunk(_io__raw_body, self, self._root)
elif _on == u"zTXt":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.CompressedTextChunk(_io__raw_body, self, self._root)
elif _on == u"fcTL":
self._raw_body = self._io.read_bytes(self.len)
_io__raw_body = KaitaiStream(BytesIO(self._raw_body))
self.body = Png.FrameControlChunk(_io__raw_body, self, self._root)
else:
self.body = self._io.read_bytes(self.len)
self.crc = self._io.read_bytes(4)
class BkgdIndexed(KaitaiStruct):
"""Background chunk for images with indexed palette."""
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.palette_index = self._io.read_u1()
class Point(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.x_int = self._io.read_u4be()
self.y_int = self._io.read_u4be()
@property
def x(self):
if hasattr(self, '_m_x'):
return self._m_x
self._m_x = (self.x_int / 100000.0)
return getattr(self, '_m_x', None)
@property
def y(self):
if hasattr(self, '_m_y'):
return self._m_y
self._m_y = (self.y_int / 100000.0)
return getattr(self, '_m_y', None)
class BkgdGreyscale(KaitaiStruct):
"""Background chunk for greyscale images."""
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.value = self._io.read_u2be()
class ChrmChunk(KaitaiStruct):
"""
.. seealso::
Source - https://www.w3.org/TR/png/#11cHRM
"""
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.white_point = Png.Point(self._io, self, self._root)
self.red = Png.Point(self._io, self, self._root)
self.green = Png.Point(self._io, self, self._root)
self.blue = Png.Point(self._io, self, self._root)
class IhdrChunk(KaitaiStruct):
"""
.. seealso::
Source - https://www.w3.org/TR/png/#11IHDR
"""
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.width = self._io.read_u4be()
self.height = self._io.read_u4be()
self.bit_depth = self._io.read_u1()
self.color_type = KaitaiStream.resolve_enum(Png.ColorType, self._io.read_u1())
self.compression_method = self._io.read_u1()
self.filter_method = self._io.read_u1()
self.interlace_method = self._io.read_u1()
class PlteChunk(KaitaiStruct):
"""
.. seealso::
Source - https://www.w3.org/TR/png/#11PLTE
"""
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.entries = []
i = 0
while not self._io.is_eof():
self.entries.append(Png.Rgb(self._io, self, self._root))
i += 1
class SrgbChunk(KaitaiStruct):
"""
.. seealso::
Source - https://www.w3.org/TR/png/#11sRGB
"""
class Intent(Enum):
perceptual = 0
relative_colorimetric = 1
saturation = 2
absolute_colorimetric = 3
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.render_intent = KaitaiStream.resolve_enum(Png.SrgbChunk.Intent, self._io.read_u1())
class CompressedTextChunk(KaitaiStruct):
"""Compressed text chunk effectively allows to store key-value
string pairs in PNG container, compressing "value" part (which
can be quite lengthy) with zlib compression.
.. seealso::
Source - https://www.w3.org/TR/png/#11zTXt
"""
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.keyword = (self._io.read_bytes_term(0, False, True, True)).decode(u"UTF-8")
self.compression_method = KaitaiStream.resolve_enum(Png.CompressionMethods, self._io.read_u1())
self._raw_text_datastream = self._io.read_bytes_full()
self.text_datastream = zlib.decompress(self._raw_text_datastream)
class FrameDataChunk(KaitaiStruct):
"""
.. seealso::
Source - https://wiki.mozilla.org/APNG_Specification#.60fdAT.60:_The_Frame_Data_Chunk
"""
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.sequence_number = self._io.read_u4be()
self.frame_data = self._io.read_bytes_full()
class BkgdTruecolor(KaitaiStruct):
"""Background chunk for truecolor images."""
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.red = self._io.read_u2be()
self.green = self._io.read_u2be()
self.blue = self._io.read_u2be()
class GamaChunk(KaitaiStruct):
"""
.. seealso::
Source - https://www.w3.org/TR/png/#11gAMA
"""
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.gamma_int = self._io.read_u4be()
@property
def gamma_ratio(self):
if hasattr(self, '_m_gamma_ratio'):
return self._m_gamma_ratio
self._m_gamma_ratio = (100000.0 / self.gamma_int)
return getattr(self, '_m_gamma_ratio', None)
class BkgdChunk(KaitaiStruct):
"""Background chunk stores default background color to display this
image against. Contents depend on `color_type` of the image.
.. seealso::
Source - https://www.w3.org/TR/png/#11bKGD
"""
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):
_on = self._root.ihdr.color_type
if _on == Png.ColorType.indexed:
self.bkgd = Png.BkgdIndexed(self._io, self, self._root)
elif _on == Png.ColorType.truecolor_alpha:
self.bkgd = Png.BkgdTruecolor(self._io, self, self._root)
elif _on == Png.ColorType.greyscale_alpha:
self.bkgd = Png.BkgdGreyscale(self._io, self, self._root)
elif _on == Png.ColorType.truecolor:
self.bkgd = Png.BkgdTruecolor(self._io, self, self._root)
elif _on == Png.ColorType.greyscale:
self.bkgd = Png.BkgdGreyscale(self._io, self, self._root)
class PhysChunk(KaitaiStruct):
""""Physical size" chunk stores data that allows to translate
logical pixels into physical units (meters, etc) and vice-versa.
.. seealso::
Source - https://www.w3.org/TR/png/#11pHYs
"""
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.pixels_per_unit_x = self._io.read_u4be()
self.pixels_per_unit_y = self._io.read_u4be()
self.unit = KaitaiStream.resolve_enum(Png.PhysUnit, self._io.read_u1())
class FrameControlChunk(KaitaiStruct):
"""
.. seealso::
Source - https://wiki.mozilla.org/APNG_Specification#.60fcTL.60:_The_Frame_Control_Chunk
"""
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.sequence_number = self._io.read_u4be()
self.width = self._io.read_u4be()
if not self.width >= 1:
raise kaitaistruct.ValidationLessThanError(1, self.width, self._io, u"/types/frame_control_chunk/seq/1")
if not self.width <= self._root.ihdr.width:
raise kaitaistruct.ValidationGreaterThanError(self._root.ihdr.width, self.width, self._io, u"/types/frame_control_chunk/seq/1")
self.height = self._io.read_u4be()
if not self.height >= 1:
raise kaitaistruct.ValidationLessThanError(1, self.height, self._io, u"/types/frame_control_chunk/seq/2")
if not self.height <= self._root.ihdr.height:
raise kaitaistruct.ValidationGreaterThanError(self._root.ihdr.height, self.height, self._io, u"/types/frame_control_chunk/seq/2")
self.x_offset = self._io.read_u4be()
if not self.x_offset <= (self._root.ihdr.width - self.width):
raise kaitaistruct.ValidationGreaterThanError((self._root.ihdr.width - self.width), self.x_offset, self._io, u"/types/frame_control_chunk/seq/3")
self.y_offset = self._io.read_u4be()
if not self.y_offset <= (self._root.ihdr.height - self.height):
raise kaitaistruct.ValidationGreaterThanError((self._root.ihdr.height - self.height), self.y_offset, self._io, u"/types/frame_control_chunk/seq/4")
self.delay_num = self._io.read_u2be()
self.delay_den = self._io.read_u2be()
self.dispose_op = KaitaiStream.resolve_enum(Png.DisposeOpValues, self._io.read_u1())
self.blend_op = KaitaiStream.resolve_enum(Png.BlendOpValues, self._io.read_u1())
@property
def delay(self):
"""Time to display this frame, in seconds."""
if hasattr(self, '_m_delay'):
return self._m_delay
self._m_delay = (self.delay_num / (100.0 if self.delay_den == 0 else self.delay_den))
return getattr(self, '_m_delay', None)
class InternationalTextChunk(KaitaiStruct):
"""International text chunk effectively allows to store key-value string pairs in
PNG container. Both "key" (keyword) and "value" (text) parts are
given in pre-defined subset of iso8859-1 without control
characters.
.. seealso::
Source - https://www.w3.org/TR/png/#11iTXt
"""
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.keyword = (self._io.read_bytes_term(0, False, True, True)).decode(u"UTF-8")
self.compression_flag = self._io.read_u1()
self.compression_method = KaitaiStream.resolve_enum(Png.CompressionMethods, self._io.read_u1())
self.language_tag = (self._io.read_bytes_term(0, False, True, True)).decode(u"ASCII")
self.translated_keyword = (self._io.read_bytes_term(0, False, True, True)).decode(u"UTF-8")
self.text = (self._io.read_bytes_full()).decode(u"UTF-8")
class TextChunk(KaitaiStruct):
"""Text chunk effectively allows to store key-value string pairs in
PNG container. Both "key" (keyword) and "value" (text) parts are
given in pre-defined subset of iso8859-1 without control
characters.
.. seealso::
Source - https://www.w3.org/TR/png/#11tEXt
"""
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.keyword = (self._io.read_bytes_term(0, False, True, True)).decode(u"iso8859-1")
self.text = (self._io.read_bytes_full()).decode(u"iso8859-1")
class AnimationControlChunk(KaitaiStruct):
"""
.. seealso::
Source - https://wiki.mozilla.org/APNG_Specification#.60acTL.60:_The_Animation_Control_Chunk
"""
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_frames = self._io.read_u4be()
self.num_plays = self._io.read_u4be()
class TimeChunk(KaitaiStruct):
"""Time chunk stores time stamp of last modification of this image,
up to 1 second precision in UTC timezone.
.. seealso::
Source - https://www.w3.org/TR/png/#11tIME
"""
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.year = self._io.read_u2be()
self.month = self._io.read_u1()
self.day = self._io.read_u1()
self.hour = self._io.read_u1()
self.minute = self._io.read_u1()
self.second = self._io.read_u1()