DuneGraph
From Just Solve the File Format Problem
DuneGraph is a graphics program for the Atari ST line of computers. .dc1 files are compressed .dg1 files.
Contents |
Identification
.dc1 files begin with ASCII "DGC".
.dg1 files begin with ASCII "DGU".
PaintShop plus *.PSC (st high resolution)
*.DA4 (st high resolution, double height)
*.DA4 files are simple screen dumps:
64000 bytes image data (uncompressed, thus 640x800)
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64000 bytes total for file
*.PSC files are compressed:
6 bytes file id ["tm89PS"]
1 word version [0xCB = 2.03]
1 byte ? [always 2]
1 byte ? [always 1]
1 word image width in pixels - 1 [always 639]
1 word image height in pixels - 1 [always 399]
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14 bytes total for header
? image data:
The image data is not compressed based on pixels, but rather scan lines. Starting at the
top and working downward. There are 9 unique codes:
Codes:
0 set current line all white (0x00)
10 copy line above (next byte + 1) times
12 copy line above (next byte + 256 + 1) times
99 copy from stream 80 * 400 lines (full image)
100 fill next line with (next byte) as line style [(b << 8 ) | b]
102 fill next line with (next 2 bytes) as line style [(b1 << 8) | b2]
110 copy from stream 80 bytes to current line
200 set current line all black (0xFF)
255 marks end of file (stop process codes)
'line style' mentioned above is a reference to VDI function vsl_udsty(), set user-defined
line style pattern. Essentially, fill that line with the bit pattern.
