While working on the content for the upcoming post about the musical resources of the LucasArts video game Indiana Jones and the Fate of Atlantis^[1] (or simply FOA), I wanted to develop a small tool to extract the color palettes and background images from the game.

I thought that having the background images for each environment in the game would eventually be useful to quickly recall the events of the game at any given moment in the story.

The Python code I wrote to export these images is hosted on my GitHub page, here^[2]. To make it work, you need to have the original FOA game files: the index file ATLANTIS.000 and the resource file ATLANTIS.001.

Below a table with all the room images and palettes extracted with the tool:

Room Number	Room Name	Background Image	Color Palette
1	col-offic
2	col-hall_
3	col-basem
4	col-attic
5	col-store
6	col-archi
7	col-catro
8	wallet___
9	natl-geo_
10	sop-theat
11	sop-stage
12	sop-sides
13	de-ice-ex
14	dig-top__
15	sop-study
16	a2-skelet
17	a2-digger
18	a2-rube__
19	de-azores
20	sahara___
21	a3-pit-to
22	a3-god-ma
23	a3-center
24	deadroom_
25	sub-volca
26	de-ice-in
27	mc-hotel_
28	mc-seance
29	af-cas-fl
30	a3-god-hi
31	a2-cu-rob
32	bal-deser
33	lab-crete
35	a1-2-bot_
36	a1-o-mach
37	a1-o-pool
39	sub-1-ins
40	sub-2-ins
41	sub-conn-
42	sal-surfa
43	cr-bro-ex
44	cr-bro-in
45	digger-ri
46	a1-canal_
47	cu-uberma
48	a1-darkro
49	th-dock__
50	labyrinth
51	catacombs
52	labwat-1_
53	lab-subwa
54	lab-hide_
55	a3-maze__
56	lab-eleva
57	lab-three
58	transit__
59	lab-mapro
60	lab-goldb
61	labwat-2_
62	nazi-labo
63	th-landsc
64	af-cas-st
65	af-cas-ho
66	sub-under
67	af-atl-ex
68	logo_____
69	th-dig-ex
70	mc-chase_
71	mc-smashu
72	th-dig-in
73	af-atl-in
74	cu-microt
75	map-world
76	de-yuc-ex
77	de-yuc-in
78	af-cas-ov
79	cu-neckla
80	af-launch
81	lockrock_
82	sal-under
83	cu-plato_
84	cu-rube__
85	a1-nw-top
86	a1-ne-top
87	a1-sw-top
88	a1-se-top
89	end-volca
90	end-v2___
91	a1-2-dark
92	atlan-1__
93	atlan-2__
94	a2-generi
95	bal-sea__
96	endscene_
97	a1-cagero
98	_________

• The game data does not include rooms 34 and 38;
• The room 15 (sop-study) contains a section that will never be visited within the game;
• I suspect that room 51 (catacombs) is never visited during the game, as if it were a work-in-progress that was mistakenly saved in the resources;
• What are the these three vertical strips 89, 90, and 98?

The images from LucasArts video games were stored in the resource file in a compressed format. They were "sliced" into vertical strips, each 8 pixels wide, and then the strip data was compressed using a sort of custom RLE algorithm^[3], which could change depending on the graphic content of each strip.

Building the decoder wasn’t exactly straightforward because I found few references online, and in some cases, even conflicting ones. During my experiments, I encountered interesting glitch effects, such as those caused by an incorrect increment of the color pointer within the palette in the codec1.

If the codec1 implementation is as follows

while pixel_left > 0:
  if bitReader.read_bit():
    if not bitReader.read_bit():
      color_index = bitReader.read_bits( palette_index_size )
      inc = -1
    else:
      if bitReader.read_bit():
        inc = -inc
      color_index += inc

  image_writer.write_pixel( i, COLOR_LOOKUP_TABLE[ color_index ], 1, direction )
  pixel_left -= 1

... everything works correctly, but if instead of inc = -1 we use inc = +1, here's what happens:

Codec1 glitch Image

The tool I developed was heavily inspired by other similar tools that can be found with a simple web search.

Moreover, it wouldn't have been possible to implement it without the vast amount of resources and documentation available on the ScummVM project website and elsewhere. Below is a non-exhaustive list:

• Some tool I found here and there: ScummEx, ScummRevisited, and LucasRipper to name a few;
• ScummVM tech ref: Room resources (Scumm V1);
• ScummVM tech ref: Image resources;
• Super useful article with a deep dive into image encoding and decoding;

^	[1]	Indiana Jones and the Fate of Atlantis wiki page
^	[2]	Custom python FOA palette and background images extraction tool
^	[3]	RLE algorithm wiki page