ben-blinkenlights/ubb-vga/ccube.c

/*
 * ccube.c - Color mapper based on color cube model
 *
 * Written 2011 by Werner Almesberger
 * Copyright 2011 Werner Almesberger
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */


#include <stdint.h>

#include "ubb-vga.h"


#define	W_RGB	(256*0.5)
#define	W_Y	(256*0.25)
#define	W_0	(256*0.125)


static struct col {
	uint8_t r, g, b;
} col[16];


uint8_t ccube_map(uint8_t r, uint8_t g, uint8_t b)
{
	unsigned best = 0;
	int best_i = 0;
	unsigned d;
	int i;

	for (i = 0; i != 16; i++) {
		d = (r-col[i].r)*(r-col[i].r)+
		    (g-col[i].g)*(g-col[i].g)+
		    (b-col[i].b)*(b-col[i].b);
		if (!i || d < best) {
			best = d;
			best_i = i;
		}
	}
	return best_i;
}


void ccube_init(void)
{
	int i;

	for (i = 0; i != 16; i++) {
		col[i].r = W_0+(i & R_VAL ? W_RGB : 0)+(i & Y_VAL ? W_Y : 0);
		col[i].g = W_0+(i & G_VAL ? W_RGB : 0)+(i & Y_VAL ? W_Y : 0);
		col[i].b = W_0+(i & B_VAL ? W_RGB : 0)+(i & Y_VAL ? W_Y : 0);
	}
}