RGBPIX(2G) RGBPIX(2G)
NAME
RGB, rgbpix, rdcolmap, wrcolmap - handle color screens
SYNOPSIS
ulong rgbpix(Bitmap *b, RGB rgb)
void rdcolmap(Bitmap *b, RGB *map)
void wrcolmap(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 posi-
tions.
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 2^(2^ldepth), giving the col-
ors 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 bit-
map, if possible. (The hardware might not allow this.)
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.
SEE ALSO
graphics(2)
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