RGBPIX(2G)
NAME
RGB, rgbpix, rdcolmap, wrcolmap − handle color screens
SYNOPSIS
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.)
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
Plan 9 — January 03, 1993