请教高手，如何将RGB转化为HSI(50分)

本人正做图像处理软件，需要将真彩色的图像进行亮色分离，请教高手算法如何。？

int RgbToHsi(struct RgbTriadStruct *RgbTriadStructPtr,

struct HsiTriadStruct *HsiTriadStructPtr)

{

double R, G, B, Sum, Quotient;

double Radians, Angle, MinValue, MaxValue, TempDouble1, TempDouble2;

R = ((double) RgbTriadStructPtr->Red) / 255.0;

G = ((double) RgbTriadStructPtr->Green) / 255.0;

B = ((double) RgbTriadStructPtr->Blue) / 255.0;

Sum = R + G + B;

HsiTriadStructPtr->Intensity = Sum / 3.0;

MinValue = (R < G) ? R : G;

MinValue = (B < MinValue) ? B : MinValue;

MaxValue = (R > G) ? R : G;

MaxValue = (B > MaxValue) ? B : MaxValue;

if (HsiTriadStructPtr->Intensity < 0.00001)

HsiTriadStructPtr->Saturation = ZERO_SATURATION;

else

HsiTriadStructPtr->Saturation = 1.0 - (3.0 * MinValue) / Sum;

if (MinValue == MaxValue)

{

HsiTriadStructPtr->Hue = UNDEFINED_HUE;

HsiTriadStructPtr->Saturation = ZERO_SATURATION;

return 0;

}

TempDouble1 = (((R - G) + (R - B)) / 2.0);

TempDouble2 = (R - G)*(R - G) + (R - B)*(G - B);

Quotient = (TempDouble1 / sqrt(TempDouble2));

if (Quotient > 0.99999999999999999)

Radians = 0.0;

else if (Quotient < -0.99999999999999999)

Radians = 3.1415926535;

else

Radians = acos(TempDouble1 / sqrt(TempDouble2));

Angle = Radians * DEGREES_PER_RADIAN;

if (B > G)

HsiTriadStructPtr->Hue = 360.0 - Angle;

else

HsiTriadStructPtr->Hue = Angle;

return 0;

}

int HsiToRgb(struct HsiTriadStruct *HsiTriadStructPtr,

struct RgbTriadStruct *RgbTriadStructPtr)

{

double r, g, b, Hue, Fraction, MaxDouble;

if (HsiTriadStructPtr->Saturation == ZERO_SATURATION)

{

if (HsiTriadStructPtr->Hue == UNDEFINED_HUE)

{

RgbTriadStructPtr->Red =

RgbTriadStructPtr->Green =

RgbTriadStructPtr->Blue =

HsiTriadStructPtr->Intensity * 255.0 + 0.5;

} else

{

printf("/n/nHsiToRgb: Illegal HSI hue value (saturation == 0)");



printf("/nHue == %5.3f, Saturation = %5.3f, Intensity == %5.3f",



HsiTriadStructPtr->Hue,

HsiTriadStructPtr->Saturation,

HsiTriadStructPtr->Intensity);

}

return 0;

}

if (HsiTriadStructPtr->Hue > 0.0 &amp;&amp;

HsiTriadStructPtr->Hue <= 120.0 )

{

b = (1.0 - HsiTriadStructPtr->Saturation) / 3.0;

Hue = HsiTriadStructPtr->Hue;

Fraction = (HsiTriadStructPtr->Saturation *

cos(Hue / DEGREES_PER_RADIAN))

/

cos((60.0 - Hue) / DEGREES_PER_RADIAN);

r = (1.0 + Fraction) / 3.0;

g = 1.0 - (r + b);

} else if (HsiTriadStructPtr->Hue > 120.0 &amp;&amp;

HsiTriadStructPtr->Hue <= 240.0 )

{

Hue = HsiTriadStructPtr->Hue - 120.0;

r = (1.0 - HsiTriadStructPtr->Saturation) / 3.0;

Fraction = (HsiTriadStructPtr->Saturation *

cos(Hue / DEGREES_PER_RADIAN))

/

cos((60.0 - Hue) / DEGREES_PER_RADIAN);

g = (1.0 + Fraction) / 3.0;

b = 1.0 - (r + g);

} else

{



Hue=

HsiTriadStructPtr->Hue - 240.0;

g = (1.0 - HsiTriadStructPtr->Saturation) / 3.0;

Fraction = (HsiTriadStructPtr->Saturation *

cos(Hue / DEGREES_PER_RADIAN))

/

cos((60.0 - Hue) / DEGREES_PER_RADIAN);

b = (1.0 + Fraction) / 3.0;

r = 1.0 - (g + b);

}

MaxDouble = ((r > g) ? r : g);

MaxDouble = ((MaxDouble > b) ? MaxDouble : b);

if (3.0 * HsiTriadStructPtr->Intensity * MaxDouble > 1.0)

HsiTriadStructPtr->Intensity = (1.0 / (3.0 * MaxDouble));

r *= 255.0;

g *= 255.0;

b *= 255.0;

RgbTriadStructPtr->Red =

(USGC) ((3.0 * HsiTriadStructPtr->Intensity * r) + 0.5);

RgbTriadStructPtr->Green =

(USGC) ((3.0 * HsiTriadStructPtr->Intensity * g) + 0.5);

RgbTriadStructPtr->Blue =

(USGC) ((3.0 * HsiTriadStructPtr->Intensity * b) + 0.5);



return 0;

}

H=arccos((R-G)+(R-B)/2/sqrt((R-G)*(R-G)+(R-B)(G-B))
S=1-3/(R+G+B)*min(R,G,B)
I=1/3*(R+G+B)

多人接受答案了。