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<HTML>
<HEAD><TITLE>RCT Graphics Files</TITLE></HEAD>
<BODY BGCOLOR="#ffffff" BACKGROUND="bkground.jpg">
<H1 ALIGN="Center">RCT GRAPHICS FILES</H1>
<H5><A HREF="index.html">Back to RCT home</A></H5>
<P>
Henry Winkelstein has provided invaluable information about the csg1i.dat
and csg1.dat RollerCoaster Tycoon graphics files. A reproduction of the original
forum discussion is <A HREF="/web/20130104221643/http://www.strategyplanet.com/rctuk/tid/csg/csg1dat.html">here</A>! I have expanded that
information some and the material presented here is more complete and, hopefully,
more understandable. This material is intended for programmers so if you
don't know the difference between a "word" and a "signed two byte variable"
then you need to learn some basics before tyring to use this information
in any way.
<P>
The csg1.dat file consists of 16 byte structures as follows (in Delphi code):
<P>
<CODE>TGraphicRecord = packed record</CODE><BR>
<CODE> StartAddress : longword;</CODE><BR>
<CODE> Width, Height, Xoffset, Yoffset : smallint; // signed two byte
variables</CODE><BR>
<CODE> Flags : word; </CODE><BR>
<CODE> unused : word // to pad the structure to 16 bytes</CODE><BR>
<CODE>end;</CODE>
<P>
The <B>StartAddress</B> is the starting address in csg1.dat for this graphic.
<B>Width</B> and <B>Height</B> are the width and height of the extracted
graphic image. <B>Xoffset</B> is the horizontal distance from the "reference
point" of the graphic to its left edge. Since most of the graphics are for
isometric tiles, the reference point is usually the base height of the corner
of the isometric diamond facing the viewer. <B>Yoffset</B> is a similar value
for the vertical (top) of the graphic. <B>Flags</B> indicates the type of
graphic contained at this location. Only the lowest nibble (4 bits) is
significant, mask out the upper twelve bits. A value of 1 indicates a direct
bitmap image. A value of 5 indicates a compacted bitmap image. A value of
8 indicates palette definitions.
<P>
Note: within the pixel information, a value of 00 indicates "transparent"
and the remapable colors are indicated by index values in the ranges: 0A
to 15, CA to D5 and F3 to FE. These are the colors of ride parts that a user
can select within the game. When the graphic is loaded, the user's color
selection will determine which palette values are actually used.
<P>
<B>Flags</B> = 1: Direct bitmap - Use the Width and Height to scan the bytes
of csg1.dat the appropriate number of times. Each byte of csg1.dat is a palette
index for that pixel.
<P>
<B>Flags</B> = 5: Compacted bitmap - the <B>StartAddress</B> points to a
table of row start offsets (word wide). You can jump to
StartAddress+RowStartOffset0 to start looking at the data. Each row line
consists of one or more scan elements. Each scan element begins with a two
byte header. The first byte indicates the number of bytes of data for that
element. In addition, the MSB of the first byte is a flag. If set, this is
the last scan element on this row. If not set, there will be another scan
element following this one. The second byte of the scan element header is
an offset value. The scan element begins at that offset from the left edge
of the graphic. Pixels which are skipped are to be "transparent". To illustrate,
imagine a graphic of a vertical ladder. Most of the scan lines contain
transparent pixels except for two scan elements of the ladder rails.
Consequently, there would be two scan elements for such rows. The first might
be: 04 06 67 7B 7B 61 where the header(04 06) indicates this scan element
contains four pixels which begin six pixels from the left edge. The pixels
are to be drawn with the palette colors specified by the palette indices
67, 7B, 7B, 61. This might be followed be another scan element such as: 84
16 67 7B 7B 61. The high bit of the first byte is set to indicate that this
element in the last element on the scan line. In this scan element; there
are four pixels and they begin twentytwo pixels from the left edge.
<P>
<B>Flags</B> = 8: palette entries - <B>Width</B> indicates how many three
byte entries (Blue, Green, Red) will be obtained. The starting index for
the palette entries is determined by <B>Xoffset</B>.
<P>
Here are the locations of Palette definitions within my version of csg1.dat
(for LL)
<P>
00076569: 236 entries start at: 10<BR>
0007682D: 236 entries start at: 10<BR>
00076AF1: 15 entries start at: 16<BR>
00076B1E: 15 entries start at: 32<BR>
00076B4B: 15 entries start at: 48<BR>
00076B78: 15 entries start at: 80<BR>
00076BA5: 15 entries start at: 96<BR>
00076BD2: 15 entries start at: 112<BR>
00076BFF: 15 entries start at: 16<BR>
00076C2C: 15 entries start at: 32<BR>
00076C59: 15 entries start at: 48<BR>
00076C86: 15 entries start at: 80<BR>
00076CB3: 15 entries start at: 96<BR>
00076CE0: 15 entries start at: 112<BR>
00076D0D: 3 entries start at: 144<BR>
00076D16: 3 entries start at: 160<BR>
00076D1F: 3 entries start at: 176<BR>
023627E5: 236 entries start at: 10<BR>
0236DFA0: 236 entries start at: 10<BR>
0237C4F4: 236 entries start at: 10<BR>
023C77B8: 236 entries start at: 10 <BR>
</BODY></HTML>