Extract sprite type 3-1 in TWG

extract_sprite_3-1.py

# -*- coding: utf-8 -*-

# Extract sprites

import argparse
import struct
import os

# mode 13h resolution
MONITOR_WIDTH = 320
MONITOR_HEIGHT = 200
# bright pink
SPRITE_BACKGROUND = (255, 0, 255)

parser = argparse.ArgumentParser(description='Extract sprites.')
parser.add_argument('-p', required=True, help='palette file', dest='pal')
parser.add_argument('-f', required=True, help='compressed sprites file',
                    dest='spr')
args = parser.parse_args()

# read palette
pal = []
with open(args.pal, 'rb') as f:
  for i in range(256):
    buf = f.read(3)
    buf = struct.unpack('<BBB', buf)
    pal.append((buf[0], buf[1], buf[2]))

# extract sprites
with open(args.spr, 'rb') as f:
  f.seek(0, os.SEEK_END)
  file_len = f.tell()
  f.seek(0, os.SEEK_SET)

  # header
  f.seek(0x42, os.SEEK_SET)

  # maybe, number of sprites.
  buf = f.read(2)
  buf = struct.unpack('<H', buf)
  num = buf[0]
  assert 44 >= num
  #print("number of sprites: " + str(num))

  # zero padding
  f.seek(60, os.SEEK_CUR)

  for n in range(num):
    buf = f.read(4)
    buf = struct.unpack('<I', buf)
    length = buf[0]
    
    # width
    buf = f.read(2)
    buf = struct.unpack('<H', buf)
    width = buf[0]
    assert MONITOR_WIDTH >= width

    # height
    buf = f.read(2)
    buf = struct.unpack('<H', buf)
    height = buf[0]
    assert MONITOR_HEIGHT >= height

    # unknown
    f.read(2)
    f.read(2)
    
    # unknown
    f.read(1)
    f.read(1)
    f.read(1)
    f.read(1)
    f.read(1)

    # number of compressed chunks
    buf = f.read(2)
    buf = struct.unpack('<H', buf)
    chunks = buf[0]

    # reset monitor
    monitor = range(MONITOR_WIDTH * MONITOR_HEIGHT)
    monitor = []
    for i in range(MONITOR_WIDTH * MONITOR_HEIGHT):
      monitor.append(SPRITE_BACKGROUND)

    # draw a sprite on monitor
    l = 0
    idx = 0
    for c in range(chunks):
      buf = f.read(2)
      buf = struct.unpack('<H', buf)
      blanks = buf[0]
      idx = idx + blanks

      buf = f.read(1)
      buf = struct.unpack('<B', buf)
      drawn = 4 * buf[0]

      buf = f.read(1)
      buf = struct.unpack('<B', buf)
      drawn = drawn + buf[0]
   
      l = l + 2 + 1 + 1 + drawn
 
      for d in range(drawn):
        buf = f.read(1)
        buf = struct.unpack('<B', buf)
        pal_idx = buf[0]
        monitor[idx] = pal[pal_idx]
        idx = idx + 1

    # I do not know why length is not match.
    # I have decided to ignore remain bytes.
    #
    # The characte/golem-f.bcr has mismatch.
    assert (2 + l) <= length
    if (2 + l) < length:
      f.read(length - 2 - l)

    # write a sprite to file
    out_name = os.path.basename(args.spr)
    out_name = out_name + '.%05d' % n + '.ppm'

    with open(out_name, 'w') as out:
      out.write('P3\n')
      out.write('%d %d\n' % (width, height))
      out.write('255\n')
      
      for h in range(height):
        for w in range(width):
          rgb = monitor[320 * h + w]
          out.write('%d %d %d\n' % (rgb[0], rgb[1], rgb[2]))

  assert f.tell() == file_len