# AIPS HELP file for STEPLEVS in 31DEC19

#### As of Wed Oct 23 4:00:30 2019

STEPLEVS: Proc to set RGBLEVS to a repeated sequence of colors

### INPUTS

```LEVS     \$                          Contour levels
RGBGAMMA \$       0.0                Gamma correction parameter
RGBLEVS  @       0.0        1.0     RGB for each LEVS in order
```

### HELP SECTION

```STEPLEVS
Proc:  This procedure will set RGBGAMMA if it is not positive, will
examine the LEVS values and set them to -10 to -1 followed by 1
to 10 if they are not set.  Then it will determine a list of
colors of length given by an immediate argument to STEPLEVS.
It will set RGBLEVS so that the first positive LEVS and first
negative LEVS will be the first color in the list, the 2nd
positive and 2nd negative LEVS will be the second color in the
list, and so forth.  If there are more positive or more
negative LEVS that there are colors in the list, then the list
is reused.  Thus, if there are 6 colors and 10 positive LEVS,
the first 6 LEVS gets colors 1 through 6, and the remaining 4
LEVS get colors 1 through 4.

Before using this procedure you must enter
RUN SETRGBL
which will define this and 3 other procedures.  Any time you
change the values in LEVS, you should then enter
STEPLEVS (x)
again to select the new set of colors.  Note that these colors
are similar to those of the verb TVPSEUDO with Button C (first
three patterns)

The colors are for X=5
pure blue, cyan, green, yellow, red
For x=6
pure blue, cyan, green, yellow, red, magenta
For x=7
pure blue, cyan, green, yellow, red, magenta, white
For x=8 a sequence suggested by Lincoln Greenhill,
approximately magenta, blue, cyan, green, yellow, orange,
red, brown
For x=9 a sequence suggested by Renzo Sanchisi
approximately grey, magenta, dark blue, light blue,
dark green, light green, yellow, orange, red
For x=10 a sequence suggested by GYPSY
approximately grey, cyan, blue, dark green, red, orange,
yellow, light green, magenta, white

RGBGAMMA...If 0 on input, set to 2.2.  The gamma correction
parameter to adjust colors (value used = input value to
the 1/RGBGAMMA power).  Larger values make more pastel
colors.
LEVS.......Contour level multipliers.  Up to 30 values in increasing
order - if all 0 on input, set to -10 to -1, 1, to 10.
Defines which values require colors and what their range
should be.  Thus, if you change LEVS, you should execute
STEPLEVS again.
X..........Immediate argument to procedure.