C语言，可在Object-C中调用

#define UNDEFINED 0

typedef struct {float r, g, b;} RGBType;

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

// Theoretically, hue 0 (pure red) is identical to hue 6 in these transforms. Pure

// red always maps to 6 in this implementation. Therefore UNDEFINED can be

// defined as 0 in situations where only unsigned numbers are desired.

RGBType RGBTypeMake(float r, float g, float b);

HSVType HSVTypeMake(float h, float s, float v);

HSVType RGB_to_HSV( RGBType RGB );

RGBType HSV_to_RGB( HSVType HSV );

#include

#include "HSV.h"

inline RGBType RGBTypeMake(float r, float g, float b)

{

RGBType rgb = {r, g, b};

return rgb;

}

inline HSVType HSVTypeMake(float h, float s, float v)

{

HSVType hsv = {h, s, v};

return hsv;

}

HSVType RGB_to_HSV( RGBType RGB )

{

// RGB are each on [0, 1]. S and V are returned on [0, 1] and H is

// returned on [0, 1]. Exception: H is returned UNDEFINED if S==0.

float R = RGB.r, G = RGB.g, B = RGB.b, v, x, f;

int i;

x = fminf(R, G);

x = fminf(x, B);

v = fmaxf(R, G);

v = fmaxf(v, B);

if(v == x)

return HSVTypeMake(UNDEFINED, 0, v);

f = (R == x) ? G - B : ((G == x) ? B - R : R - G);

i = (R == x) ? 3 : ((G == x) ? 5 : 1);

return HSVTypeMake(((i - f /(v - x))/6), (v - x)/v, v);

}

RGBType HSV_to_RGB( HSVType HSV )

{

// H is given on [0, 1] or UNDEFINED. S and V are given on [0, 1].

// RGB are each returned on [0, 1].

float h = HSV.h * 6, s = HSV.s, v = HSV.v, m, n, f;

int i;

if (h == 0) h=.01;

if(h == UNDEFINED)

return RGBTypeMake(v, v, v);

i = floorf(h);

f = h - i;

if(!(i & 1)) f = 1 - f; // if i is even

m = v * (1 - s);

n = v * (1 - s * f);

switch (i)

{

case 6:

case 0: return RGBTypeMake(v, n, m);

case 1: return RGBTypeMake(n, v, m);

case 2: return RGBTypeMake(m, v, n);

case 3: return RGBTypeMake(m, n, v);

case 4: return RGBTypeMake(n, m, v);

case 5: return RGBTypeMake(v, m, n);

}

return RGBTypeMake(0, 0, 0);

}