


PLSCMAP1L(3)                PLplot API               PLSCMAP1L(3)


NAME
       plscmap1l  -  Set color map1 colors using a piece-wise linear relation-
       ship

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 typi-
       cally 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]magnitudeHLSsatura-
       tion[0, 1]magnitude

       Redacted form: plscmap1l(itype, pos, coord1, coord2, coord3, rev)

       This function is used in examples 8,11,15,20,21.

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

       npts (PLINT, input)
              number of control points





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PLSCMAP1L(3)                PLplot API               PLSCMAP1L(3)


       pos (PLFLT *, input)
              position for each control point (between 0.0 and 1.0, in ascend-
              ing 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.































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