GFA Raytrace file format

GFA Raytrace    *.SUL *.SUH (st low/high resolution image uncompressed)
                *.SCL *.SCH (st low/high resolution image compressed)
                *.SAL *.SAH (st low/high resolution animation compressed)

SUL/SCL/SCH details:

6 bytes    file id in plain ASCII text: "sul" or "scl" + cr/lf
             "sul' = uncompressed, "scl" = compressed
3 bytes    size factor in plain ASCII text: "1", "2", "4", or "8" + cr/lf
             factor = ASC(factor) - 48
             image height = image height/factor
? bytes    palette (first scan line is always black, not included in the file)
             palette size = 18400/factor
? bytes    image data
             bitmap size = 32000/factor
             
Uncompressed fixed image sizes:
Factor    Size in bytes
1         50408
2         25208
4         12608
8         6308

SUH details: (similar to Degas *.PI3)

1 word         resolution flag [always 2]
16 words       palette (should be ignored, seems to contain bogus values)
32000 bytes    image data
-----------
32034 bytes    total file size

SAL/SAH detail: (up to 10 frames maximum)

6 bytes     file id in plain ASCII text: "sal" or "sah" + cr/lf
              "sal' = st low resolution, "sah" = st high resolution
1 long      frame count - 1
1 long      size factor [1, 2, 4, or 8]
              image height = image height/factor
1 long      image data size
10 longs    offsets to all 10 frames from the start of the file [0 for unused entries]
Repeated for each frame:
  ?         palette, size = 18400/factor
  ?         compressed image data, uncompressed size = 32000/factor

Notes: Currently there is no description of the compression method.
The layout of the rasters and how to calculate the color of a pixel at a
given x/y coordinate is unknown.

Note: 68K decompression code can be found here:
      http://gfa.atari-users.net/gfx/

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