bionic (3) plscmap1l.3plplot.gz

Provided by: plplot-doc_5.13.0+dfsg-6ubuntu2_all bug

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 the cmap1 intensity index (0.0-1.0) 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, and 21.


ARGUMENTS
       itype (PLBOOL(3plplot), input)
              true: RGB, false: HLS.

       npts (PLINT(3plplot), input)
              number of control points

       intensity (PLFLT_VECTOR(3plplot), input)
              A vector containing the cmap1 intensity index (0.0-1.0) in ascending order for each control point.

       coord1 (PLFLT_VECTOR(3plplot), input)
              A vector containing the first coordinate (H or R) for each control point.

       coord2 (PLFLT_VECTOR(3plplot), input)
              A vector containing the second coordinate (L or G) for each control point.

       coord3 (PLFLT_VECTOR(3plplot), input)
              A vector containing the third coordinate (S or B) for each control point.

       alt_hue_path (PLBOOL_VECTOR(3plplot), input)
              A vector (with npts - 1 elements) containing the alternative interpolation  method  Boolean  value
              for  each  control  point interval.  (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.

                                                 November, 2017                               PLSCMAP1L(3plplot)