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下面的代码是用C++完成的RGB和HSL颜色转换。注意它们的分量的取值范围。
#include "stdafx.h"
#define min3v(v1, v2, v3) ((v1)>(v2)? ((v2)>(v3)?(v3):(v2)):((v1)>(v3)?(v3):(v2)))
#define max3v(v1, v2, v3) ((v1)<(v2)? ((v2)<(v3)?(v3):(v2)):((v1)<(v3)?(v3):(v1)))
typedef struct
{
BYTE red; // [0,255]
BYTE green; // [0,255]
BYTE blue; // [0,255]
}COLOR_RGB;
typedef struct
{
float hue; // [0,360]
float saturation; // [0,100]
float luminance; // [0,100]
}COLOR_HSL;
// Converts RGB to HSL
static void RGBtoHSL(/*[in]*/const COLOR_RGB *rgb, /*[out]*/COLOR_HSL *hsl)
{
float h=0, s=0, l=0;
// normalizes red-green-blue values
float r = rgb->red/255.f;
float g = rgb->green/255.f;
float b = rgb->blue/255.f;
float maxVal = max3v(r, g, b);
float minVal = min3v(r, g, b);
// hue
if(maxVal == minVal)
{
h = 0; // undefined
}
else if(maxVal==r && g>=b)
{
h = 60.0f*(g-b)/(maxVal-minVal);
}
else if(maxVal==r && g<b)
{
h = 60.0f*(g-b)/(maxVal-minVal) + 360.0f;
}
else if(maxVal==g)
{
h = 60.0f*(b-r)/(maxVal-minVal) + 120.0f;
}
else if(maxVal==b)
{
h = 60.0f*(r-g)/(maxVal-minVal) + 240.0f;
}
// luminance
l = (maxVal+minVal)/2.0f;
// saturation
if(l == 0 || maxVal == minVal)
{
s = 0;
}
else if(0<l && l<=0.5f)
{
s = (maxVal-minVal)/(maxVal+minVal);
}
else if(l>0.5f)
{
s = (maxVal-minVal)/(2 - (maxVal+minVal)); //(maxVal-minVal > 0)?
}
hsl->hue = (h>360)? 360 : ((h<0)?0:h);
hsl->saturation = ((s>1)? 1 : ((s<0)?0:s))*100;
hsl->luminance = ((l>1)? 1 : ((l<0)?0:l))*100;
}
// Converts HSL to RGB
static void HSLtoRGB(const COLOR_HSL *hsl, COLOR_RGB *rgb)
{
float h = hsl->hue; // h must be [0, 360]
float s = hsl->saturation/100.f; // s must be [0, 1]
float l = hsl->luminance/100.f; // l must be [0, 1]
float R, G, B;
if(hsl->saturation == 0)
{
// achromatic color (gray scale)
R = G = B = l*255.f;
}
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