PCX FILES

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				DESCRIPTION
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  The PCX extention (.pcx) has become a standard used to specify graphic
files stored in the PCX File Format.  This file format is used to store
pictures efficiently using a run-length encoding (RLE) technique to compress
the image and save disk space.  This file format was originally developed for
the PC by Zsoft for a paint program called Paintbrush.  Most games today use
256-color PCX files.  The race simulators by Papyrus use 256-color PCX files
mainly to store the color palettes, but also to store those nifty images that
you see at the end of a race and at the end of the season.  The cars are
painted with colors 16-175 from the palette.

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				STRUCTURE
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  The PCX file is divided into three distint sections.  The first section in
the header which contains the attributes of the image.  The second section
contains the image data itself.  The third section contains the 256-color
palette.

SECTION ONE: The Header
-----------------------
    BYTE    PURPOSE
    ----    --------------------------------------------------
    000     Manufacturer: Always set to zero
    001     Version: Always set to five for 256-color
    002     Encoding: Always set to one
    003     Bits-per-pixel: Always set to 8 for 256-color
    004-005 X-MIN: Top left x-coordinate
    006-007 Y-MIN: Top left y-coordinate
    008-009 X-MAX: Width of the image
    010-011 Y-MAX: Height of the image
    012-013 H-RES: Horizontal resolution of the image
    014-015 V-RES: Vertical resolution of the image
    016-063 EGA Palette: Not used in 256-color files
    064     Reserved: For future use
    065     Color Planes: Number of color planes
    066-067 Bytes-per-line: Num of bytes in 1 line of pixels
    068-069 Palette Type: Always set to 2 for color palettes
    070-127 Filler: Used to round the header out to 128 bytes

SECTION TWO: The Image
----------------------
  The image of the PCX file begins at byte 128.  The PCX file uses a
run-length encoding (RLE) technique to compress the image and save disk
space.  If the first value P in the image is less than 192, it represents one
pixel of color value P.  If the first value is 192 or more, it represents the
count of pixels plus 192 that have the following byte's color value.  This is
repeated until every pixel in the image is accounted for.

SECTION THREE: The 256-Color Palette
------------------------------------
  Each color is represented by one value for red, one value for green, and
one value for blue.  Each of these values is stored as one byte in the
palette.  Since there are 256 colors, the 256-color palette is the last 768
bytes of the PCX file.  The range for each red/green/blue value is 0 to 63,
with 0 being darkest and 63 being the brightest.  A PCX file stores the
red/green/blue values multiplied by four.  For tracks, only the last 80
colors (176-255) are editable.  The first 175 colors are used for the cars
and other things such as the flagman's flags.

-------------------------
-Corey Rueckheim
-rueck_cw@cslab.uwlax.edu