COLOR(3) COLOR(3)
NAME
cmap2rgb, cmap2rgba, rgb2cmap - colors and color maps
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <draw.h>
int rgb2cmap(int red, int green, int blue)
int cmap2rgb(int col)
int cmap2rgba(int col)
DESCRIPTION
These routines convert between `true color' red/green/blue
triples and the Plan 9 color map. See color(7) for a
description of RGBV, the standard color map.
Rgb2cmap takes a trio of color values, scaled from 0 (no
intensity) to 255 (full intensity), and returns the index of
the color in RGBV closest to that represented by those val-
ues.
Cmap2rgb decomposes the color of RGBV index col and returns
a 24-bit integer with the low 8 bits representing the blue
value, the next 8 representing green, and the next 8 repre-
senting red. Cmap2rgba decomposes the color of RGBV index
col and returns a 32-bit integer with the low 8 bits repre-
senting an alpha value, defined to be 255, and the next 8
representing blue, then green, then red, as for cmap2rgba
shifted up 8 bits. This 32-bit representation is the format
used by draw(3) and memdraw(3) library routines that take
colors as arguments.
SOURCE
/usr/local/plan9/src/libdraw
SEE ALSO
graphics(3), allocimage(3), draw(3), image(7), color(7)
Page 1 Plan 9 (printed 12/31/24)