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/* hsv2rgb.c
* Convert Hue Saturation Value to Red Green Blue
*
* P.J. 08-Aug-98 ( P. A. Jacobs <peterj@mech.uq.edu.au> )
*
* Reference:
* D. F. Rogers
* Procedural Elements for Computer Graphics
* McGraw Hill 1985
*/
#include "hsv2rgb.h"
int hsv2rgb( struct hsv_colour *hsv, struct rgb_colour *rgb ) {
/*
* Purpose:
* Convert HSV values to RGB values
* All values are in the range [0.0 .. 1.0]
*/
float S, H, V, F, M, N, K;
int I;
S = hsv->s; /* Saturation */
H = hsv->h; /* Hue */
V = hsv->v; /* value or brightness */
if ( S == 0.0 ) {
/*
* Achromatic case, set level of grey
*/
rgb->r = V;
rgb->g = V;
rgb->b = V;
} else {
/*
* Determine levels of primary colours.
*/
if (H >= 1.0) {
H = 0.0;
} else {
H = H * 6;
} /* end if */
I = (int) H; /* should be in the range 0..5 */
F = H - I; /* fractional part */
M = V * (1 - S);
N = V * (1 - S * F);
K = V * (1 - S * (1 - F));
if (I == 0) { rgb->r = V; rgb->g = K; rgb->b = M; }
if (I == 1) { rgb->r = N; rgb->g = V; rgb->b = M; }
if (I == 2) { rgb->r = M; rgb->g = V; rgb->b = K; }
if (I == 3) { rgb->r = M; rgb->g = N; rgb->b = V; }
if (I == 4) { rgb->r = K; rgb->g = M; rgb->b = V; }
if (I == 5) { rgb->r = V; rgb->g = M; rgb->b = N; }
} /* end if */
return 0;
} /* end function hsv2rgb */
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