term% cat index.txt COLOR(2) System Calls Manual COLOR(2)
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(6) 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 clos‐
est to that represented by those values.
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 representing red. Cmap2rgba decom‐
poses the color of RGBV index col and returns a 32-bit integer with the
low 8 bits representing 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(2) and
memdraw(2) library routines that take colors as arguments.
SOURCE
/sys/src/libdraw
SEE ALSO
graphics(2), allocimage(2), draw(2), image(6), color(6)
COLOR(2)