plscmap1la.3plplot man page

plscmap1la — Set cmap1 colors and alpha transparency using a piece-wise linear relationship


plscmap1la(itype, npts, intensity, coord1, coord2, coord3, alpha, alt_hue_path)


This is a variant of plscmap1l(3plplot) that supports alpha channel transparency. It sets cmap1 colors using a piece-wise linear relationship between cmap1 intensity index (from 0. to 1.) and position in HLS or RGB color space (see the PLplot documentation) with alpha transparency value (0.0 - 1.0). It may be called at any time.

Redacted form: plscmap1la(itype, intensity, coord1, coord2, coord3, alpha, alt_hue_path)

This function is used in example 30.


itype (PLBOOL, input)

true: RGB, false: HLS.

npts (PLINT, input)

number of control points

intensity (const PLFLT *, input)

position 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

alpha (const PLFLT *, input)

the alpha transparency value 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).


Many developers (who are credited at have contributed to PLplot over its long history.

See Also

PLplot documentation at


August, 2015 PLplot API