avr-lib/lib/color.c

#include <avr/io.h>
#include <util/delay.h>
#include <stdint.h>

#include "iopins.h"
#include "nsdelay.h"
#include "color.h"


// --- HSL ---

#ifdef HSL_LINEAR
const uint8_t FADE_128[] =
{
	0,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  3,  3,  3,  4,  4,  4,  4,
	5,  5,  6,  6,  6,  7,  7,  8,  8,  8,  9,  10, 10, 10, 11, 12, 13, 14,
	14, 15, 16, 17, 18, 20, 21, 22, 24, 26, 27, 28, 30, 31, 32, 34, 35, 36,
	38, 39, 40, 41, 42, 44, 45, 46, 48, 49, 50, 52, 54, 56, 58, 59, 61, 63,
	65, 67, 68, 69, 71, 72, 74, 76, 78, 80, 82, 85, 88, 90, 92, 95, 98, 100,
	103, 106, 109, 112, 116, 119, 122, 125, 129, 134, 138, 142, 147, 151,
	153, 156, 160, 163, 165, 170, 175, 180, 185, 190, 195, 200, 207, 214, 218,
	221, 225, 228, 232, 234, 241, 248, 254, 255
};
#endif

// based on: https://github.com/lewisd32/avr-hsl2rgb
xrgb_t hsl_xrgb(const hsl_t cc)
{
	// 0 .. 256*3
	const uint16_t hh = (uint16_t) cc.h * 3;
	const uint8_t hue_mod = hh % 256;

	uint8_t r_temp, g_temp, b_temp;
	if (hh < 256)
	{
		r_temp = hue_mod ^ 255;
		g_temp = hue_mod;
		b_temp = 0;
	}
	else if (hh < 512)
	{
		r_temp = 0;
		g_temp = hue_mod ^ 255;
		b_temp = hue_mod;
	}
	else if (hh < 768)
	{
		r_temp = hue_mod;
		g_temp = 0;
		b_temp = hue_mod ^ 255;
	}
	else
	{
		r_temp = 0;
		g_temp = 0;
		b_temp = 0;
	}

	const uint8_t inverse_sat = (cc.s ^ 255);

	xrgb_t rgb;

	uint8_t t8;
	uint16_t t16;

#ifdef HSL_LINEAR
	const uint8_t bri = FADE_128[cc.l >> 1];
#else
	const uint8_t bri = cc.l;
#endif

	t8 = r_temp;
	t16 = t8 * cc.s + t8;
	t16 = t16 + t8;
	t8 = t16 >> 8;
	t8 = t8 + inverse_sat;
	t16 = t8 * bri;
	t16 = t16 + t8;
	t8 = t16 >> 8;
	rgb.r = t8;

	t8 = g_temp;
	t16 = t8 * cc.s;
	t16 = t16 + t8;
	t8 = t16 >> 8;
	t8 = t8 + inverse_sat;
	t16 = t8 * bri;
	t16 = t16 + t8;
	t8 = t16 >> 8;
	rgb.g = t8;

	t8 = b_temp;
	t16 = t8 * cc.s;
	t16 = t16 + t8;
	t8 = t16 >> 8;
	t8 = t8 + inverse_sat;
	t16 = t8 * bri;
	t16 = t16 + t8;
	t8 = t16 >> 8;
	rgb.b = t8;

	return rgb;
}