NAME

cmap2rgb, cmap2rgba, rgb2cmap − colors and color maps

SYNOPSIS

­#include <u.h>
­#include <libc.h>
­#include <draw.h>

intrgb2cmap(int red, int green, int blue)

intcmap2rgb(int col)

intcmap2rgba(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 ALSO

graphics(2), allocimage(2), draw(2), image(6), color(6)

Plan 9  —  December 11, 1999