Provided by: plplot-doc_5.10.0-0ubuntu5_all 
NAME
plscmap1l - Set cmap1 colors using a piece-wise linear relationship
SYNOPSIS
plscmap1l(itype, npts, intensity, coord1, coord2, coord3, alt_hue_path)
DESCRIPTION
Set cmap1 colors using a piece-wise linear relationship between intensity index (from 0. to 1.) of cmap1
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 input cmap1
intensity indices and HLS (or RGB). Between these points, linear interpolation is used which gives a
smooth variation of color with intensity index. 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 cmap1 intensity indices.
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 cmap1 intensity index and the associated three coordinates in HLS or
RGB space. The first point must correspond to position = 0, and the last to position = 1.
The default behaviour is for the hue to be linearly interpolated between the control points. Since the
hue lies in the range [0, 360] this corresponds to interpolation around the "front" of the color wheel
(red<->green<->blue<->red). If alt_hue_path[i] is true, then an alternative interpolation is used between
control points i and i+1. If hue[i+1]-hue[i] > 0 then interpolation is between hue[i] and hue[i+1] -
360, otherwise between hue[i] and hue[i+1] + 360. You can consider this as interpolation around the
"back" or "reverse" of the color wheel. Specifying alt_hue_path=NULL is equivalent to setting
alt_hue_path[] = false for every control point.
Examples of interpolation Huealt_hue_pathcolor scheme[120 240]falsegreen-cyan-blue[240 120]falseblue-
cyan-green[120 240]truegreen-yellow-red-magenta-blue[240 120]trueblue-magenta-red-yellow-green
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, intensity, coord1, coord2, coord3, alt_hue_path)
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
intensity (const PLFLT *, input)
intensity index for each control point (between 0.0 and 1.0, in ascending order)
coord1 (const PLFLT *, input)
first coordinate (H or R) for each control point
coord2 (const PLFLT *, input)
second coordinate (L or G) for each control point
coord3 (const PLFLT *, input)
third coordinate (S or B) for each control point
alt_hue_path (const PLBOOL *, input)
alternative interpolation method flag for each control point. (alt_hue_path[i] refers to the
interpolation interval between the i and i + 1 control points).
AUTHORS
Many developers (who are credited at http://plplot.sourceforge.net/credits.php) have contributed to
PLplot over its long history.
SEE ALSO
PLplot documentation at http://plplot.sourceforge.net/documentation.php.
February, 2014 PLSCMAP1L(3plplot)