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Plan 9 - man page for rgbpix (plan9 section 2)

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RGBPIX(2)										RGBPIX(2)

       RGB, rgbpix, rdcolmap, wrcolmap - handle color screens

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

       ulong rgbpix(Bitmap *b, RGB rgb)

       void  rdcolmap(Bitmap *b, RGB *map)

       void  wrcolmap(Bitmap *b, RGB *map)

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

	      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  argu-
       ment, 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 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.)



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

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