ZLS colour tables

The ZLS System used text file based colour tables. The colour tables are written in unecrypted text format in .ctab files. The complete set of tables including this file are available as a single download (ZIP, 106kB). This also includes code for reading colour table files and writing 8 bit TIFFs.

Each file has a simple header indicating the exact variation of the format, and the number of colours in the table, followed by the colour indices and RGB values (or index + single grayscale values for simple gray tables).

There are three basic formats, indicated by the first line of the ctab file:

  • 0: Decimal values used, i.e. 0-255, or 0-65535
  • 1: Hexadecimal values used: ie 00 - FF or 0000 - FFFF
  • 2: Floating point values: 0.0 - 1.0

The next line indicates the number of bits per value. It an be 8 or 16 for decimal and hexadecimal formats, and 16 for floating point format.

The next line indicates the number of colour components, 1 (grayscale) or 3 (RGB), then the number of colours follows, and is usually 256.

Finally the indices and values follow, 1 entry per line. For grayscale there are two columns, index then value, and for RGB there are 4 columns, index and red, green, blue values.

Format Examples:

13.ps.ctab: 0.1.rss.ctab:0 31.123.ctab: 0.2.gray.ctab:
1
8
3
256
0 00 00 7f
1 00 00 83
2 00 00 87
3 00 00 8b
1
16
3
256
0 ffff ffff ffff
1 fefe fefe f7bd
2 fdfd fdfd ef7b
3 fcfc fcfc e739
0
8
3
256
0 0 0 0
1 0 0 0
2 95 0 114
3 98 0 112
1
8
1
256
0 ff
1 fe
2 fd
3 fc
Hex 8 bit values, RGB Hex 16 bit values, RGB Decimal 8 bit values, RGB Hex 8 bit values, Grayscale

Download code for reading colour table files and writing 8 bit TIFFs (ZIP, 106kB)

 

Colour Tables Preview

01.rss
ctabs/01.rss
04.grey_mod
ctabs/04.grey_mod
10.red
ctabs/10.red
13.ps
ctabs/13.ps
16.ag2
ctabs/16.ag2
19.goldblue
ctabs/19.goldblue
22.r3
ctabs/22.r3
25.p2
ctabs/25.p2
28.air
ctabs/28.air
31.123
ctabs/31.123
34.blob1
ctabs/34.blob1
37.contour
ctabs/37.contour
 
02.gray
ctabs/02.gray
08.blue
ctabs/08.blue
11.blackbody
ctabs/11.blackbody
14.stern2
ctabs/14.stern2
17.ag3
ctabs/17.ag3
20.r1
ctabs/20.r1
23.r4
ctabs/23.r4
26.p3
ctabs/26.p3
29.water
ctabs/29.water
32.barb
ctabs/32.barb
35.blob2
ctabs/35.blob2
38.lograinbow
ctabs/38.lograinbow
40.bbyw
ctabs/40.bbwy
03.gray_inverse
ctabs/03.gray_inverse
09.green
ctabs/09.green
12.idlstd
ctabs/12.idlstd
15.ag1
ctabs/15.ag1
18.bluegold
ctabs/18.bluegold
21.r2
ctabs/21.r2
24.p1
ctabs/24.p1
27.tim
ctabs/27.tim
30.earth
ctabs/30.earth
33.barb2
ctabs/33.barb2
36.carl
ctabs/36.carl
39.subdued
ctabs/39.subdued
 

Updated:  13 December 2017/Responsible Officer:  RSAA Director/Page Contact:  Webmaster