.pcx file format: Python parsing library

PCX is a bitmap image format originally used by PC Paintbrush from ZSoft Corporation. Originally, it was a relatively simple 128-byte header + uncompressed bitmap format, but latest versions introduced more complicated palette support and RLE compression.

There's an option to encode 32-bit or 16-bit RGBA pixels, and thus it can potentially include transparency. Theoretically, it's possible to encode resolution or pixel density in the some of the header fields too, but in reality there's no uniform standard for these, so different implementations treat these differently.

PCX format was never made a formal standard. "ZSoft Corporation Technical Reference Manual" for "Image File (.PCX) Format", last updated in 1991, is likely the closest authoritative source.

This page hosts a formal specification of .pcx file format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime 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 kaitaistruct

Code

Parse a local file and get structure in memory:

data = Pcx.from_file("path/to/local/file.pcx")

Or parse structure from a bytes:

from kaitaistruct import KaitaiStream, BytesIO

raw = b"\x00\x01\x02..."
data = Pcx(KaitaiStream(BytesIO(raw)))

After that, one can get various attributes from the structure by invoking getter methods like:

data.hdr # => get hdr

Python source code to parse .pcx file format

pcx.py

# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

from pkg_resources import parse_version
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum


if parse_version(kaitaistruct.__version__) < parse_version('0.9'):
    raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))

class Pcx(KaitaiStruct):
    """PCX is a bitmap image format originally used by PC Paintbrush from
    ZSoft Corporation. Originally, it was a relatively simple 128-byte
    header + uncompressed bitmap format, but latest versions introduced
    more complicated palette support and RLE compression.
    
    There's an option to encode 32-bit or 16-bit RGBA pixels, and thus
    it can potentially include transparency. Theoretically, it's
    possible to encode resolution or pixel density in the some of the
    header fields too, but in reality there's no uniform standard for
    these, so different implementations treat these differently.
    
    PCX format was never made a formal standard. "ZSoft Corporation
    Technical Reference Manual" for "Image File (.PCX) Format", last
    updated in 1991, is likely the closest authoritative source.
    
    .. seealso::
       Source - https://web.archive.org/web/20100206055706/http://www.qzx.com/pc-gpe/pcx.txt
    """

    class Versions(Enum):
        v2_5 = 0
        v2_8_with_palette = 2
        v2_8_without_palette = 3
        paintbrush_for_windows = 4
        v3_0 = 5

    class Encodings(Enum):
        rle = 1
    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._raw_hdr = self._io.read_bytes(128)
        _io__raw_hdr = KaitaiStream(BytesIO(self._raw_hdr))
        self.hdr = Pcx.Header(_io__raw_hdr, self, self._root)

    class Header(KaitaiStruct):
        """
        .. seealso::
           - "ZSoft .PCX FILE HEADER FORMAT" - https://web.archive.org/web/20100206055706/http://www.qzx.com/pc-gpe/pcx.txt
        """
        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"\x0A":
                raise kaitaistruct.ValidationNotEqualError(b"\x0A", self.magic, self._io, u"/types/header/seq/0")
            self.version = KaitaiStream.resolve_enum(Pcx.Versions, self._io.read_u1())
            self.encoding = KaitaiStream.resolve_enum(Pcx.Encodings, self._io.read_u1())
            self.bits_per_pixel = self._io.read_u1()
            self.img_x_min = self._io.read_u2le()
            self.img_y_min = self._io.read_u2le()
            self.img_x_max = self._io.read_u2le()
            self.img_y_max = self._io.read_u2le()
            self.hdpi = self._io.read_u2le()
            self.vdpi = self._io.read_u2le()
            self.palette_16 = self._io.read_bytes(48)
            self.reserved = self._io.read_bytes(1)
            if not self.reserved == b"\x00":
                raise kaitaistruct.ValidationNotEqualError(b"\x00", self.reserved, self._io, u"/types/header/seq/11")
            self.num_planes = self._io.read_u1()
            self.bytes_per_line = self._io.read_u2le()
            self.palette_info = self._io.read_u2le()
            self.h_screen_size = self._io.read_u2le()
            self.v_screen_size = self._io.read_u2le()


    class TPalette256(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(1)
            if not self.magic == b"\x0C":
                raise kaitaistruct.ValidationNotEqualError(b"\x0C", self.magic, self._io, u"/types/t_palette_256/seq/0")
            self.colors = [None] * (256)
            for i in range(256):
                self.colors[i] = Pcx.Rgb(self._io, self, self._root)



    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()


    @property
    def palette_256(self):
        """
        .. seealso::
           - "VGA 256 Color Palette Information" - https://web.archive.org/web/20100206055706/http://www.qzx.com/pc-gpe/pcx.txt
        """
        if hasattr(self, '_m_palette_256'):
            return self._m_palette_256 if hasattr(self, '_m_palette_256') else None

        if  ((self.hdr.version == Pcx.Versions.v3_0) and (self.hdr.bits_per_pixel == 8) and (self.hdr.num_planes == 1)) :
            _pos = self._io.pos()
            self._io.seek((self._io.size() - 769))
            self._m_palette_256 = Pcx.TPalette256(self._io, self, self._root)
            self._io.seek(_pos)

        return self._m_palette_256 if hasattr(self, '_m_palette_256') else None