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B.3 Sun raster files
The Sun raster file format consists of a header followed by a series
of unsigned 1-byte integers that represents the bit-pattern. Bits
are scanline oriented, and each row must contain an even number of
bytes. The predefined 1-bit
patterns in GMT have dimensions of 64 by 64, but other sizes will be
accepted when using the -GpP option. The Sun header structure
is outline in Table B.3.
Table B.3:
Structure of a Sun rasterfile.
Parameter |
Description |
int ras_magic |
Magic number |
int ras_width |
Width (pixels) of image |
int ras_height |
Height (pixels) of image |
int ras_depth |
Depth (1, 8, 24, 32 bits) of pixel |
int ras_length |
Length (bytes) of image |
int ras_type |
Type of file; see RT_* below |
int ras_maptype |
Type of colormap; see RMT_* below |
int ras_maplength |
Length (bytes) of following map |
|
After the header, the color map (if ras_maptype is not RMT_NONE)
follows for ras_maplength bytes, followed by an image of
ras_length bytes. Some related definitions are given in Table B.4.
Table B.4:
Sun macro definitions relevant to rasterfiles.
Macro name |
Description |
RAS_MAGIC |
0x59a66a95 |
RT_STANDARD |
1 (Raw pixrect image in 68000 byte order) |
RT_BYTE_ENCODED |
2 (Run-length compression of bytes) |
RT_FORMAT_RGB |
3 ([X]RGB instead of [X]BGR) |
RMT_NONE |
0 (ras_maplength is expected to be 0) |
RMT_EQUAL_RGB |
1 (red[ras_maplength/3],green[],blue[]) |
|
Numerous public-domain programs exist, such as xv and
convert (in the ImageMagick package), that will translate
between various rasterfile formats such as tiff, gif, jpeg, and
Sun raster. Raster patterns may be created with GMT plotting
tools by generating PostScript plots that can be rasterized
by ghostscript and translated into the right raster format.
Next: C. Making GMT Encapsulated
Up: B. GMT file formats
Previous: B.2.4 Native binary grid
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Paul Wessel
2006-01-01