COLOR(2)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 closest 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
decomposes 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
graphics(2),
allocimage(2),
draw(2),
image(6),
color(6)