.TH RGBPIX 2G
.SH NAME
RGB, rgbpix, rdcolmap, wrcolmap \- handle color screens
.SH SYNOPSIS
.PP
.ta \w'\fLulong 'u
.B
ulong	rgbpix(Bitmap *b, RGB rgb)
.PP
.B
void	rdcolmap(Bitmap *b, RGB *map)
.PP
.B
void	wrcolmap(Bitmap *b, RGB *map)
.fi
.SH DESCRIPTION
Colors are described by the red, green, and blue
light intensities, in an
.B RGB
datum:
.IP
.EX
.ta 6n
typedef
struct RGB {
	ulong red;
	ulong green;
	ulong blue;
} RGB;
.EE
.PP
Black is represented by zero in all three positions and
white has the maximum
.B unsigned
.B long
value in all three positions.
.PP
Some of the graphics functions, such as
.I point
(see
.IR bitblt (2)),
take a
.I pixel value
argument, which is a single
.B unsigned
.BR long .
For a given bitmap,
.I rgbpix
returns the pixel value with a color closest to
the color represented by the
.I rgb
argument.
.PP
There is a
.I colormap
associated with each Bitmap.  A colormap is an array of
.BR RGB s,
of length
.if t 2\u\s82\u\s6\fIldepth\fP\d\d\s10,
.if n 2^(2^\fIldepth\fP),
giving the colors for pixels 0, 1, 2, etc.
.PP
.I Rdcolmap
reads the colormap for the given bitmap into the provided
.IR map ,
which must have enough space to hold it.
.I Wrcolmap
associates the given colormap with the given bitmap, if possible.
(The hardware might not allow this.)
.SH 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.
.SH "SEE ALSO"
.IR graphics (2)