1RAS_PALETTE(5NCARG)              NCAR GRAPHICS             RAS_PALETTE(5NCARG)
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NAME

6       ras_palette - format descriptions for palette files for NCAR View
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SYNOPSIS

9       palette_file.pal
10       palette_file.txt
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DESCRIPTION

13       NCAR  View supports a binary as well as a textual format for color pal‐
14       ettes.
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16       The binary format is compatible with NCSA HDF  and  must  have  a  file
17       extension  of ".pal". The palette has a red, a green, and a blue table,
18       each with 256 single unsigned byte entries. A 0 represents no intensity
19       for  a  given color, and a 255 full intensity. In the file, the palette
20       is stored as:
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22                 R0 R1 ... R255 G0 G1 ... G255 B0 B1 ... B255
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24       for a total of 768 bytes.
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26       The textual format can be created by a program or manually with a  text
27       editor.  It  provides  for 256 RGB entries but also allows for a sparse
28       color table. In the latter case, missing  values  are  calculated  from
29       those  provided using linear interpolation. If unspecified, the 0 entry
30       defaults to black and the 255 entry to white.  Each color palette entry
31       has the following format:
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33                 index_number red green blue
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35       where  index_number, red, green, and blue are all integers in the range
36       0 to 255.
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EXAMPLES

39       All of the examples below deal with textual color palettes.
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41       Setting Entries
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43              Set color index 0 to black.
44                        0 0 0 0
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46              Set color index 255 to white
47                        255 255 255 255
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49       Grayscale Ramp
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51              Let's suppose you have a file named "my.txt" and it has just two
52              lines  in  it:  the  black entry and the white entry from above.
53              This will produce a grayscale color  palette,  where  the  table
54              starts  at black and ramps up to white; since only entries 0 and
55              255 are specified, the remaining indicies are interpolated.
56                        0 0 0 0
57                        255 255 255 255
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59              (Note: An empty palette file (e.g. "empty.txt")  is  legal  and,
60              since  the 0 index defaults to black and the 255 index to white,
61              produces a grayscale ramp just as in the above example.)
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63       Temperature Color Scale
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65              Let's suppose you want entry 0 to be black,  and  the  remaining
66              indices to start at 1 with a fully-saturated blue and shift lin‐
67              early to 255 with a fully-saturated red. Only three entries  are
68              required in your file, "temp.txt".
69                        0 0 0 0
70                        1 0 0 255
71                        255 255 0 0
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SEE ALSO

74       rasview(1NCARG),rascat(1NCARG),rasgetpal(1NCARG),                 rass‐
75       plit(1NCARG),rasls(1NCARG),ras_formats(5NCARG)
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BUGS/CAVEATS

78       Color palettes are only useful with indexed-color imagery.
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81       Copyright (C) 1987-2009
82       University Corporation for Atmospheric Research
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84       The use of this Software is governed by a License Agreement.
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88NCARG                            January 1993              RAS_PALETTE(5NCARG)
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