Amiga version parsing

[RedMike]

It turns out that the Amiga version of the game (released slightly after the initial DOS release) has various changes, including:

• Some sort of map marker flagging on the combat screen pre-entering combat
• Some changes to combat sprite drawing (maybe runtime colour changing?)
• 32-colour (from a palette of 4096 possible colours) images and animations, only some of which were updated (e.g. TITLE2, BRIEFING)

While it would be interesting to be able to parse this data, it comes with the following challenges:

• Amiga is big-endian, therefore a lot of parsing code would need reworking to correctly handle endian-ness changes, which in C# is not exactly trivial
• The PIC file format is different and is turned into PIX, which has different data, packs pixel data to 1 pixel per byte (32 possible values), and has a different implementation of RLE/LZW than PIC (but also than PAN in Amiga in some ways!)
• The PAN file format is different, includes tagged chunks (easier to parse), PIX format images (but weirdly while the LZW implementation is the same as the DOS one, the RLE one is different, probably an implementation error); control data is similar but extended to u16s instead of bytes for some values

Personally I also have no idea about emulating Amiga nor working with it, to be able to run the game myself to check things out, which is a challenge in and of itself.

That said, CanadianAvenger may look into the PAN/PIX formats further and potentially document them on his site. He's already got the PAN background image being rendered which is a good start.

Overall this is very much not a priority, and would just be a nice thing to work on in future.

[RedMike]

CanadianAvenger finished the PIX/PAN investigation, and it doesn't look like the formats are too different. Important notes:

• Some images remain 16-colour images, but are still in the new format
• PIX images have a format flag similar to PIC that define if they are 16 or 32 colour
• The header for the PIX images is very different, as is the one for PAN (including a new header signature)
• The PIX image data is encoded oddly: the entire set of data is basically a set of 16-bit words, which because Amiga is Big Endian, end up flipped from Little Endian; this means the entire file basically needs streaming in to reverse the bytes to Little Endian, before processing, to prevent confusion (e.g. the last pre-image data byte, which is the 0B LZW dictionary size, appears after the first byte of the LZW data, as part of the same 16-bit word).
• The PAN data is not encoded in the same odd way
• Almost all numbers in the PAN data are 16-bit long (and stored Big Endian), including ones that make no sense like the animation Opcode/Step Type
• The jump instruction (not including jump animation step) parameter is still 16-bit long, but is stored Little Endian for some reason, despite being a pointer/offset for the jump; the animation step jump parameter and the Start Sprite parameter are also offsets and yet are stored Big Endian

Additionally, there were two separate versions of the Amiga game:

• v447.01 (2 disks) which came out soon after DOS release and is mostly the same (but includes e.g. the new briefing animation, and some really horrible music); I believe this version could not be installed on hard drive
• v447.101 (3 disks) which came out about a year later (1992) and contains some more changes: new title screen animation (not PAN or data file, seems to be code; but title2 pan is still included weirdly), new sounds for various actions that had no sounds before, simplified animations including removing a lot of the briefing sub-animations, new music track. And I believe this version could be installed on hard drive
  There seem to have been a couple small functional changes (some sort of markers on the map before entering, if the place is wire-tapped, at least), and there may or may not be graphical changes in-game outside of the image data (sprite drawing is quite odd and seems to allow for more runtime-level changes).

Still no plan to support it outright, but documenting in case people come across it later.