#include <stdio.h>
#include <math.h>


typedef struct {
    float h, s, v;
} hsvpix_t;

static void HSVtoRGB(float *r, float *g, float *b, hsvpix_t pix)
{
    int i;
    double f, p, q, t, h;

    if (pix.s == 0) {
	// achromatic (grey)
	*r = *g = *b = pix.v;
	return;
    }

    h = pix.h / 60;		// sector 0 to 5
    i = floor(h);
    f = h - i;			// factorial part of h
    p = pix.v * (1 - pix.s);
    q = pix.v * (1 - pix.s * f);
    t = pix.v * (1 - pix.s * (1 - f));

    switch (i) {
    case 0:
	*r = pix.v;
	*g = t;
	*b = p;
	break;
    case 1:
	*r = q;
	*g = pix.v;
	*b = p;
	break;
    case 2:
	*r = p;
	*g = pix.v;
	*b = t;
	break;
    case 3:
	*r = p;
	*g = q;
	*b = pix.v;
	break;
    case 4:
	*r = t;
	*g = p;
	*b = pix.v;
	break;
    default:			// case 5:
	*r = pix.v;
	*g = p;
	*b = q;
	break;
    }

}

static struct {
    float Seathresold;
    float Landthresold;
    float Tthresold;
    hsvpix_t CloudTop;
    hsvpix_t CloudBot;
    hsvpix_t SeaTop;
    hsvpix_t SeaBot;
    hsvpix_t GroundTop;
    hsvpix_t GroundBot;
} fcinfo = {
    30.0, 90.0, 100.0, {
    230, 0.2, 0.3}, {
    230, 0.0, 1.0}, {
    200.0, 0.7, 0.6}, {
    240.0, 0.6, 0.4}, {
    60.0, 0.6, 0.2}, {
    100.0, 0.0, 0.5}
};

void readfconf(char *file)
{
    FILE *fin;

    fin = fopen(file, "r");
    if (fin == NULL)
	return;

    fscanf(fin, "%g\n", &fcinfo.Seathresold);
    fscanf(fin, "%g\n", &fcinfo.Landthresold);
    fscanf(fin, "%g\n", &fcinfo.Tthresold);
    fscanf(fin, "%g %g %g\n", &fcinfo.CloudTop.h, &fcinfo.CloudTop.s,
	   &fcinfo.CloudTop.v);
    fscanf(fin, "%g %g %g\n", &fcinfo.CloudBot.h, &fcinfo.CloudBot.s,
	   &fcinfo.CloudBot.v);
    fscanf(fin, "%g %g %g\n", &fcinfo.SeaTop.h, &fcinfo.SeaTop.s,
	   &fcinfo.SeaTop.v);
    fscanf(fin, "%g %g %g\n", &fcinfo.SeaBot.h, &fcinfo.SeaBot.s,
	   &fcinfo.SeaBot.v);
    fscanf(fin, "%g %g %g\n", &fcinfo.GroundTop.h, &fcinfo.GroundTop.s,
	   &fcinfo.GroundTop.v);
    fscanf(fin, "%g %g %g\n", &fcinfo.GroundBot.h, &fcinfo.GroundBot.s,
	   &fcinfo.GroundBot.v);

    fclose(fin);

};

void falsecolor(double v, double t, float *r, float *g, float *b)
{
    hsvpix_t top, bot, c;
    double scv, sct;

    if (t < fcinfo.Tthresold) {
	if (v < fcinfo.Seathresold) {
	    /* sea */
	    top = fcinfo.SeaTop, bot = fcinfo.SeaBot;
	    scv = v / fcinfo.Seathresold;
	    sct = t / fcinfo.Tthresold;
	} else {
	    /* ground */
	    top = fcinfo.GroundTop, bot = fcinfo.GroundBot;
	    scv =
		(v - fcinfo.Seathresold) / (fcinfo.Landthresold -
					    fcinfo.Seathresold);
	    sct = t / fcinfo.Tthresold;
	}
    } else {
	/* clouds */
	top = fcinfo.CloudTop, bot = fcinfo.CloudBot;
	scv = v / 255.0;
	sct = t / 255.0;
    }

    c.s = top.s + sct * (bot.s - top.s);
    c.v = top.v + scv * (bot.v - top.v);
    c.h = top.h + scv * sct * (bot.h - top.h);

    HSVtoRGB(r, g, b, c);
};