xwd (X Window Dump) bitmap image: Ruby parsing library

xwd is a file format written by eponymous X11 screen capture application (xwd stands for "X Window Dump"). Typically, an average user transforms xwd format into something more widespread by any of xwdtopnm and pnmto... utilities right away.

xwd format itself provides a raw uncompressed bitmap with some metainformation, like pixel format, width, height, bit depth, etc. Note that technically format includes machine-dependent fields and thus is probably a poor choice for true cross-platform usage.

Application

xwd

KS implementation details

License: CC0-1.0

This page hosts a formal specification of xwd (X Window Dump) bitmap image using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Parse a local file and get structure in memory:

data = Xwd.from_file("path/to/local/file.xwd (X Window Dump) bitmap image")

Or parse structure from a string of bytes:

bytes = "\x00\x01\x02..."
data = Xwd.new(Kaitai::Struct::Stream.new(bytes))

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

data.header_size # => Size of the header in bytes

Ruby source code to parse xwd (X Window Dump) bitmap image

xwd.rb

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

require 'kaitai/struct/struct'

unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.7')
  raise "Incompatible Kaitai Struct Ruby API: 0.7 or later is required, but you have #{Kaitai::Struct::VERSION}"
end


##
# xwd is a file format written by eponymous X11 screen capture
# application (xwd stands for "X Window Dump"). Typically, an average
# user transforms xwd format into something more widespread by any of
# `xwdtopnm` and `pnmto...` utilities right away.
# 
# xwd format itself provides a raw uncompressed bitmap with some
# metainformation, like pixel format, width, height, bit depth,
# etc. Note that technically format includes machine-dependent fields
# and thus is probably a poor choice for true cross-platform usage.
class Xwd < Kaitai::Struct::Struct

  PIXMAP_FORMAT = {
    0 => :pixmap_format_x_y_bitmap,
    1 => :pixmap_format_x_y_pixmap,
    2 => :pixmap_format_z_pixmap,
  }
  I__PIXMAP_FORMAT = PIXMAP_FORMAT.invert

  BYTE_ORDER = {
    0 => :byte_order_le,
    1 => :byte_order_be,
  }
  I__BYTE_ORDER = BYTE_ORDER.invert

  VISUAL_CLASS = {
    0 => :visual_class_static_gray,
    1 => :visual_class_gray_scale,
    2 => :visual_class_static_color,
    3 => :visual_class_pseudo_color,
    4 => :visual_class_true_color,
    5 => :visual_class_direct_color,
  }
  I__VISUAL_CLASS = VISUAL_CLASS.invert
  def initialize(_io, _parent = nil, _root = self)
    super(_io, _parent, _root)
    _read
  end

  def _read
    @header_size = @_io.read_u4be
    @_raw_hdr = @_io.read_bytes((header_size - 4))
    io = Kaitai::Struct::Stream.new(@_raw_hdr)
    @hdr = Header.new(io, self, @_root)
    @_raw_color_map = Array.new(hdr.color_map_entries)
    @color_map = Array.new(hdr.color_map_entries)
    (hdr.color_map_entries).times { |i|
      @_raw_color_map[i] = @_io.read_bytes(12)
      io = Kaitai::Struct::Stream.new(@_raw_color_map[i])
      @color_map[i] = ColorMapEntry.new(io, self, @_root)
    }
    self
  end
  class Header < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @file_version = @_io.read_u4be
      @pixmap_format = Kaitai::Struct::Stream::resolve_enum(PIXMAP_FORMAT, @_io.read_u4be)
      @pixmap_depth = @_io.read_u4be
      @pixmap_width = @_io.read_u4be
      @pixmap_height = @_io.read_u4be
      @x_offset = @_io.read_u4be
      @byte_order = Kaitai::Struct::Stream::resolve_enum(BYTE_ORDER, @_io.read_u4be)
      @bitmap_unit = @_io.read_u4be
      @bitmap_bit_order = @_io.read_u4be
      @bitmap_pad = @_io.read_u4be
      @bits_per_pixel = @_io.read_u4be
      @bytes_per_line = @_io.read_u4be
      @visual_class = Kaitai::Struct::Stream::resolve_enum(VISUAL_CLASS, @_io.read_u4be)
      @red_mask = @_io.read_u4be
      @green_mask = @_io.read_u4be
      @blue_mask = @_io.read_u4be
      @bits_per_rgb = @_io.read_u4be
      @number_of_colors = @_io.read_u4be
      @color_map_entries = @_io.read_u4be
      @window_width = @_io.read_u4be
      @window_height = @_io.read_u4be
      @window_x = @_io.read_s4be
      @window_y = @_io.read_s4be
      @window_border_width = @_io.read_u4be
      @creator = (@_io.read_bytes_term(0, false, true, true)).force_encoding("UTF-8")
      self
    end

    ##
    # X11WD file version (always 07h)
    attr_reader :file_version

    ##
    # Format of the image data
    attr_reader :pixmap_format

    ##
    # Pixmap depth in pixels - in practice, bits per pixel
    attr_reader :pixmap_depth

    ##
    # Pixmap width in pixels
    attr_reader :pixmap_width

    ##
    # Pixmap height in pixels
    attr_reader :pixmap_height

    ##
    # Bitmap X offset (number of pixels to ignore at the beginning of each scan-line)
    attr_reader :x_offset

    ##
    # Byte order of image data
    attr_reader :byte_order

    ##
    # Bitmap base data size
    attr_reader :bitmap_unit

    ##
    # Bit-order of image data
    attr_reader :bitmap_bit_order

    ##
    # Bitmap scan-line pad
    attr_reader :bitmap_pad

    ##
    # Bits per pixel
    attr_reader :bits_per_pixel

    ##
    # Bytes per scan-line
    attr_reader :bytes_per_line

    ##
    # Class of the image
    attr_reader :visual_class

    ##
    # Red mask
    attr_reader :red_mask

    ##
    # Green mask
    attr_reader :green_mask

    ##
    # Blue mask
    attr_reader :blue_mask

    ##
    # Size of each color mask in bits
    attr_reader :bits_per_rgb

    ##
    # Number of colors in image
    attr_reader :number_of_colors

    ##
    # Number of entries in color map
    attr_reader :color_map_entries

    ##
    # Window width
    attr_reader :window_width

    ##
    # Window height
    attr_reader :window_height

    ##
    # Window upper left X coordinate
    attr_reader :window_x

    ##
    # Window upper left Y coordinate
    attr_reader :window_y

    ##
    # Window border width
    attr_reader :window_border_width

    ##
    # Program that created this xwd file
    attr_reader :creator
  end
  class ColorMapEntry < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @entry_number = @_io.read_u4be
      @red = @_io.read_u2be
      @green = @_io.read_u2be
      @blue = @_io.read_u2be
      @flags = @_io.read_u1
      @padding = @_io.read_u1
      self
    end

    ##
    # Number of the color map entry
    attr_reader :entry_number
    attr_reader :red
    attr_reader :green
    attr_reader :blue
    attr_reader :flags
    attr_reader :padding
  end

  ##
  # Size of the header in bytes
  attr_reader :header_size
  attr_reader :hdr
  attr_reader :color_map
  attr_reader :_raw_hdr
  attr_reader :_raw_color_map
end