NAME

RGB, rgbpix, rdcolmap, wrcolmap − handle color screens

SYNOPSIS

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

ulongrgbpix(Bitmap ∗b, RGB rgb)

voidrdcolmap(Bitmap ∗b, RGB ∗map)

voidwrcolmap(Bitmap ∗b, RGB ∗map)

DESCRIPTION

Colors are described by the red, green, and blue light intensities, in an ­RGB datum:

typedef
struct RGB {
ulong red;
ulong green;
ulong blue;
} RGB;

Black is represented by zero in all three positions and white has the maximum ­unsigned ­long value in all three positions. 

Some of the graphics functions, such as ­point (see bitblt(2)), take a ­pixel value argument, which is a single ­unsigned long.  For a given bitmap, ­rgbpix returns the pixel value with a color closest to the color represented by the ­rgb argument. 

There is a ­colormap associated with each Bitmap.  A colormap is an array of RGBs, of length 22ldepth, giving the colors for pixels 0, 1, 2, etc. 

­Rdcolmap reads the colormap for the given bitmap into the provided map, which must have enough space to hold it. ­Wrcolmap associates the given colormap with the given bitmap, if possible.  (The hardware might not allow this.) 

SOURCE

­/sys/src/libg

SEE ALSO

graphics(2)

BUGS

These functions work only for the screen bitmap.  This interface will have to be refined for screens with more than 8 bits per pixel. 

Plan 9  —  April 04, 1995