RIX File Format

In Fallout 2 there are six RIX files. All are in master.dat, in the art\splash folder, and appear when loading the game.

RIX File Structure
Files with the RIX extension appear to be a kind of ColorRIX Image File. ColorRIX is an outdated graphics editor for VGA and SVGA cards, running under MS-DOS. There were about half a dozen formats, of which Fallout 2 only used one - SCF (renamed RIX). ColorRIX came with some VGA graphics cards and a description of the format can be found on some sites with FTP archives.

This format lets/allows us to save uncompressed images in 640x480 resolution, 256 colors (indexed). It's analogous to the Microsoft Windows Bitmap File format (BMP).

All of the control values it the file are stored in little-endian format. (I.e. least-significant byte first)

Header
The header consists of ten bytes. We'll use some C-style code to describe the structure - this isn't what's actually written in the file. struct RIXheader {		char signature[4];	//file signature (RIX3 in ASCII) WORD Width; 		//width of the image (640 pixels, 0x280) WORD Height; 		//height of the image (480 pixels, 0x1E0) WORD Unknown;		//Unknown. Possibly the number of colors used. //Fallout 2 uses only one value (0xAF) in the RIX file header. } Immediately after the header is the palette.

Palette
The palette contains RGB color codes used in the picture, and consists of 256 values (256 colors), three bytes for each. Therefore, the palette is 256*3=768 bytes and starts at offset 0xA in the RIX file. struct Palette {		RGB entries[256]; }

struct RGB {		unsigned char Red; 	// Intensity (0..255) of the red component. unsigned char Green; 	// The same, for green. unsigned char Blue; 	// The same, for blue. } Only the first six bits of each byte contain values, so the color depth is 18-bit. When trying to display the image in 24-bit color, it will look dark, so each byte must be shifted two bits to the left (<< 2). After the palette is the image data.

Data
The data occupies 640*480 = 307200 bytesand starts at offset 0x30A in the RIX file. The data is the bytes that comprise the actual image. One element of data, corresponding to one pixel on the screen, occupies one byte. The value of this byte is the serial number (index) of the color in the palette, made of 256 pieces. For example, if a byte in the image is 0x5, for the representation of that pixel on the screen you need to take the fifth color from the palette; i.e. 5(color number) * 3(number of bytes for a single color in the palette) = 15. In the palette, at offset 15 (0xF) from the start, are three bytes indicating the intensities of red, green, and blue light at that pixel respectively. Pixels are stored in order left to right, top to bottom on the screen.

Legal stuff
ColorRIX format is described in the manual for the program "ColorRIX VGA Paint". Last known address of RIX Softworks (program developer): RIX SoftWorks Inc. Attn: Richard Brownback or Paul Harker 18023 Sky Park Circle, Suite J Irvine, CA 92714 Voice: 714.476.8266 Voice: 714.476.8486

Original document at teamx.ru (in russian)