/***************************************************************************
 * Func: hsi2rgb                                                           *
 *                                                                         *
 * Desc: converts a value from HSI to RGB color space                      *
 *                                                                         *
 * Params: r - normalized red                                              *
 *         g - normalized green                                            *
 *         b - normalized blue                                             *
 *         h - hue in degrees                                              *
 *         s - normalized saturation                                       *
 *         i - normalized intensity                                        *
 ***************************************************************************/

void hsi2rgb(float *r,float *g,float *b,float h,float s,float i)
    {
    float angle1, angle2, scale, temp, denom;   /* temp variables */

    if(i==0.0)    /* BLACK */
	{
	*r = 0.0;
	*g = 0.0;
	*b = 0.0;
	return;
	}
    if(s==0.0)     /* gray-scale  H is undefined*/
	{
	*r = i;
	*g = i;
	*b = i;
	return;
	}
    if(h<0.0)
	h+=360.0;
    scale = 3.0 * i;
    if(h<=120.0)
	{
	angle1=h*0.017453293;    /* convert to radians - mul by pi/180 */
	angle2=(60.0-h)*0.017453293;

	*b = (1.0-s)/3.0;
	*r = (1.0 + (s*cos(angle1)/cos(angle2)))/3.0;
	*g = 1.0-*r-*b;
	*b *= scale;
	*r *= scale;
	*g *= scale;
	}
     else if((h>120.0) && (h<=240.0))
	{
	h -= 120.0;
	angle1=h*0.017453293;    /* convert to radians - mul by pi/180 */
	angle2=(60.0-h)*0.017453293;

	*r = (1.0-s)/3.0;
	*g = (1.0 + (s*cos(angle1)/cos(angle2)))/3.0;
	*b = 1.0 - *r - *g;
	*r *= scale;
	*g *= scale;
	*b *= scale;
	}
    else
	{
	h -= 240.0;
	angle1=h*0.017453293;    /* convert to radians - mul by pi/180 */
	angle2=(60.0-h)*0.017453293;

	*g = (1.0-s)/3.0;
	*b = (1.0 + (s*cos(angle1)/cos(angle2)))/3.0;
	*r = 1.0 - *g - *b;
	*r *= scale;
	*g *= scale;
	*b *= scale;
	}
     }