tool SC3K Sprite Extractor

[thiekus 49]

So, In my spare time, I decided to decode SimCity 3000 *.IXF file (internally known as Indexed File) by reverse engineer SC3U Windows (which has PDB debug info embedded on retail SC3U.ICD, though only main executable and not complete) and SC3U Linux libSimSpr.so (not debug info but most functions and class methods were exposed). There's attempts to extracting SC3K sprites here and the same guy did share clues code which responsible to extracting SC3K from late Paul Pedriana (RIP). But so far, no one in has given working sprite extractor.

Sprite format isn't that complicated. It's actually small header that contains sprite size and color type (usually 16-bit RGB 565 or RGB 555), followed by compressed data stream. Compression used is different between SC3K and later SC3U re-release, which in SC3K sprites using MiniLZO in RGB 555 color format, and later SC3U using older iteration of RefPack (or known as Qfs in SimCity 4 and The Sims 2 community) in RGB 565 color format (some were still at RGB 555). After data stream were decompressed, there's another header contains size and transparent color used (or just straght to indexed data for sprite masks) followed by array of strides infomations. Each strides has variable length data that skips transparent color of stride beginnings. There's still unknown part which stride width often has 0x8000 flag which I ignore this time and sprites still rendered just fine. In addition it's also able to extracting buffer images which used mostly for UI elements.

My code is written on Free Pascal flavours of Object Pascal used in Lazarus. This because this project were subset of my bigger GUI application using Lazarus which I can't finish it for now due to current circumstances (hopefully at later time). There's including RefPack decompression routine which I ported Null's DBPFSharp from C#. I'm also port MiniLZO decompression function from C.

This sprite extractor source code in this Github repo or you can also use prebuilt exe from release page here. Now you can start see you favorites building sprites directly or just data mine of possibly unused sprites.

[CorinaMarie 29,618]

2 hours ago, thiekus said:

I decided to decode SimCity 3000 *.IXF file

Very impressive.  

(I've added the Gold Featured Star so your topic will also show up in the topic list on the Home Page.)

[Null 45 3,048]

2 hours ago, thiekus said:

I'm also port MiniLZO decompression function from C.

Note that the MiniLZO code is GPL 2.0, so any derived projects must have the same license. The author also offers a commercial license, which is probably what EA/Maxis were using.

[thiekus 49]

3 hours ago, Null 45 said:

Note that the MiniLZO code is GPL 2.0, so any derived projects must have the same license. The author also offers a commercial license, which is probably what EA/Maxis were using.

Yeah, that's also my concern regarding minilzo licensing. That's why I give minilzo as license exception on repo readme, though most of my other parts keep as MIT license. It's possible to build without GPL'd minilzo after stripped SC3K decompression part (obviously you'll missing ability to decompress SC3K sprites, only SC3U), though I didn't implement compiler switch to do so for this time. Since I did expose all source code needed for build under open source license, I think I didn't violate GPL.

For future ongoing "IXF Explorer" probably I'll use GPLv3 or later for GUI parts (and keep core classes/functions as MIT) because I prefer more restrictive license for bigger project.

Edit: I give some clarification on readme and some of dependent unit code which states built program is licensed as GPL v2 or later as well when linking minilzo code to comply this situation, while keep most code still under MIT.

[thiekus 49]

Updated to v0.0.2, which now able to extract sprites from *.sjs file generated by SimCity 3000 Unlimited Rendering Kit and fix quirk of SJS file itself which store sprites as resource type same as image buffer.

Now I'm wondering if I could recreate my own rendering kit program (after I implements sprites compression and bitmap importer functions of course), because current SC3URK didn't play nicely with modern Windows.

[asasnat 216]

Oh my goodness gracious. I've wanted this for so long. And it's finally here!

I hope this paves the way for reinsertion of modified sprites in the future.

[Alan Doherty 13]

Wow, what a great late Christmas present! I've been on/off looking into this for years, thought since Paul's passing that this might remain uncracked. 

Hopefully opens the door to some sort of OpenTTD-like development, which was my initial aim. Amazing work!

[Lab Rat 13]

Automated Notice Message

All posts after 1 March, 2026 @ 01:37 GMT were lost in the site crash.

We've added this message thread divider in every topic across all forums for what were then active threads. (We decided active is if the most recent extant post (from the backup) was on or after 1 January, 2026.)

This divider serves as notice that the conversation was interrupted. Answers and further discussion which used to be here have been lost. Keep this in mind when replying. Our hope is to rebuild what is missing.