NAME¶
plscmap1l - Set color map1 colors using a piece-wise linear relationship
SYNOPSIS¶
plscmap1l(
itype,
npts,
pos,
coord1,
coord2,
coord3,
rev)
DESCRIPTION¶
Set color map1 colors using a piece-wise linear relationship between position in
the color map (from 0 to 1) and position in HLS or RGB color space (see the
PLplot documentation). May be called at any time.
The idea here is to specify a number of control points that define the mapping
between palette 1 input positions (intensities) and HLS (or RGB). Between
these points, linear interpolation is used which gives a smooth variation of
color with input position. Any number of control points may be specified,
located at arbitrary positions, although typically 2 - 4 are enough. Another
way of stating this is that we are traversing a given number of lines through
HLS (or RGB) space as we move through color map1 entries. The control points
at the minimum and maximum position (0 and 1) must always be specified. By
adding more control points you can get more variation. One good technique for
plotting functions that vary about some expected average is to use an
additional 2 control points in the center (position ~= 0.5) that are the same
lightness as the background (typically white for paper output, black for crt),
and same hue as the boundary control points. This allows the highs and lows to
be very easily distinguished.
Each control point must specify the position in color map1 as well as three
coordinates in HLS or RGB space. The first point must correspond to position =
0, and the last to position = 1.
The hue is interpolated around the "front" of the color wheel
(red<->green<->blue<->red) unless the "rev" flag
is set to true, in which case interpolation (between the i and i + 1 control
point for rev[i]) proceeds around the back (reverse) side. Specifying rev=NULL
is equivalent to setting rev[]= false for every control point.
Bounds on coordinatesRGBR[0, 1]magnitudeRGBG[0, 1]magnitudeRGBB[0,
1]magnitudeHLShue[0, 360]degreesHLSlightness[0, 1]magnitudeHLSsaturation[0,
1]magnitude
Redacted form:
plscmap1l(itype, pos, coord1, coord2, coord3, rev)
This function is used in examples 8,11,12,15,20,21.
ARGUMENTS¶
- itype (PLBOOL, input)
- true: RGB, false: HLS.
- npts (PLINT, input)
- number of control points
- pos (PLFLT *, input)
- position for each control point (between 0.0 and 1.0, in
ascending order)
- coord1 (PLFLT *, input)
- first coordinate (H or R) for each control point
- coord2 (PLFLT *, input)
- second coordinate (L or G) for each control point
- coord3 (PLFLT *, input)
- third coordinate (S or B) for each control point
- rev (PLBOOL: *, input)
- reverse flag for each control point. (rev[i] refers to the
interpolation interval between the i and i + 1 control points).
AUTHORS¶
Geoffrey Furnish and Maurice LeBrun wrote and maintain PLplot. This man page was
automatically generated from the DocBook source of the PLplot documentation,
maintained by Alan W. Irwin and Rafael Laboissiere.
SEE ALSO¶
PLplot documentation at
http://plplot.sourceforge.net/resources.