PLSCMAP1L(3)                      PLplot API                      PLSCMAP1L(3)



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 8,11,15,20,21.

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.



                                November, 2007                    PLSCMAP1L(3)
