meta:
  id: pcx
  file-extension: pcx
  xref:
    justsolve: PCX
    mime:
      - image/vnd.zbrush.pcx
      - image/x-pcx
    pronom:
      # see `/enums/versions` map
      - fmt/86 # PCX 0
      - fmt/87 # PCX 2
      - fmt/88 # PCX 3
      - fmt/89 # PCX 4
      - fmt/90 # PCX 5
    wikidata: Q535473
  license: CC0-1.0
  endian: le
doc: |
  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.
doc-ref: https://web.archive.org/web/20100206055706/http://www.qzx.com/pc-gpe/pcx.txt
seq:
  - id: hdr
    type: header
    size: 128
instances:
  palette_256:
    pos: _io.size - 769
    type: t_palette_256
    if: hdr.version == versions::v3_0 and hdr.bits_per_pixel == 8 and hdr.num_planes == 1
    doc-ref: https://web.archive.org/web/20100206055706/http://www.qzx.com/pc-gpe/pcx.txt - "VGA 256 Color Palette Information"
types:
  header:
    doc-ref: https://web.archive.org/web/20100206055706/http://www.qzx.com/pc-gpe/pcx.txt - "ZSoft .PCX FILE HEADER FORMAT"
    seq:
      - id: magic
        contents: [0x0a]
        doc: |
          Technically, this field was supposed to be "manufacturer"
          mark to distinguish between various software vendors, and
          0x0a was supposed to mean "ZSoft", but everyone else ended
          up writing a 0x0a into this field, so that's what majority
          of modern software expects to have in this attribute.
      - id: version
        type: u1
        enum: versions
      - id: encoding
        type: u1
        enum: encodings
      - id: bits_per_pixel
        type: u1
      - id: img_x_min
        type: u2
      - id: img_y_min
        type: u2
      - id: img_x_max
        type: u2
      - id: img_y_max
        type: u2
      - id: hdpi
        type: u2
      - id: vdpi
        type: u2
      - id: palette_16
        size: 48
      - id: reserved
        contents: [0]
      - id: num_planes
        type: u1
      - id: bytes_per_line
        type: u2
      - id: palette_info
        type: u2
      - id: h_screen_size
        type: u2
      - id: v_screen_size
        type: u2
  t_palette_256:
    seq:
      - id: magic
        contents: [0x0c]
      - id: colors
        type: rgb
        repeat: expr
        repeat-expr: 256
  rgb:
    seq:
      - id: r
        type: u1
      - id: g
        type: u1
      - id: b
        type: u1
enums:
  versions:
    0: v2_5
    2: v2_8_with_palette
    3: v2_8_without_palette
    4: paintbrush_for_windows
    5: v3_0
  encodings:
    1: rle