cmap2rgb, cmap2rgba, rgb2cmap - colors and color maps #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)

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.

/sys/src/libdraw graphics (2), allocimage (2), draw (2), image (6), color (6)