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/** \file
* \brief HSI Color Manipulation
*
* See Copyright Notice in im_lib.h
* $Id: im_colorhsi.cpp,v 1.1 2008/10/17 06:10:16 scuri Exp $
*/
#include <math.h>
#include "im_colorhsi.h"
#include "im_color.h"
static const float rad60 = 1.0471975f;
static const float rad120 = 2.0943951f;
static const float rad180 = 3.1415926f;
static const float rad240 = 4.1887902f;
static const float rad300 = 5.2359877f;
static const float rad360 = 6.2831853f;
static const float sqrt3 = 1.7320508f;
/**********************************/
/* HSI MAX S */
/**********************************/
static void iSmax01(float h, float hr, float hb, float hg, float *h0, float *h1)
{
if (h < rad60)
{
*h0 = hb;
*h1 = hr;
}
else if (h < rad120)
{
*h0 = hb;
*h1 = hg;
}
else if (h < rad180)
{
*h0 = hr;
*h1 = hg;
}
else if (h < rad240)
{
*h0 = hr;
*h1 = hb;
}
else if (h < rad300)
{
*h0 = hg;
*h1 = hb;
}
else
{
*h0 = hg;
*h1 = hr;
}
}
float imColorHSI_Smax(float h, double cosh, double sinh, float i)
{
float hr, hb, hg, imax, h0, h1;
if (i == 0 || i == 1)
return 0.0f;
if (i == 1.0f/3.0f || i == 2.0f/3.0f)
return 1.0f;
hr = (float)(cosh / 1.5);
hg = (float)((-cosh + sinh*sqrt3)/ 3.0);
hb = (float)((-cosh - sinh*sqrt3)/ 3.0);
/* at bottom */
if (i < 1.0f/3.0f)
{
/* face B=0 */
if (h < rad120)
return -i/hb;
/* face R=0 */
if (h < rad240)
return -i/hr;
/* face G=0 */
return -i/hg;
}
/* at top */
if (i > 2.0f/3.0f)
{
/* face R=1 */
if (h < rad60 || h > rad300)
return (1-i)/hr;
/* face G=1 */
if (h < rad180)
return (1-i)/hg;
/* face B=1 */
return (1-i)/hb;
}
/* in the middle */
iSmax01(h, hr, hb, hg, &h0, &h1);
if (h == 0 || h == rad120 || h == rad240)
imax = 1.0f/3.0f;
else if (h == rad60 || h == rad180 || h == rad300)
imax = 2.0f/3.0f;
else
imax = h0 / (h0 - h1);
if (i < imax)
return -i/h0;
else
return (1-i)/h1;
}
float imColorHSI_ImaxS(float h, double cosh, double sinh)
{
float i, h0, h1;
float hr, hb, hg;
if (h == 0 || h == rad120 || h == rad240)
return 1.0f/3.0f;
if (h == rad60 || h == rad180 || h == rad300)
return 2.0f/3.0f;
hr = (float)(cosh / 1.5f);
hg = (float)((-cosh + sinh*sqrt3)/ 3.0);
hb = (float)((-cosh - sinh*sqrt3)/ 3.0);
iSmax01(h, hr, hb, hg, &h0, &h1);
i = h0 / (h0 - h1);
return i;
}
/**********************************/
/* RGB 2 HSI */
/**********************************/
void imColorRGB2HSI(float r, float g, float b, float *h, float *s, float *i)
{
float v, u;
double H;
v = r - (g + b)/2;
u = (g - b) * (sqrt3/2);
*i = (r + g + b)/3;
*s = (float)sqrt(v*v + u*u);
if (*s == 0)
*h = 360.0f; /* by definition */
else
{
H = atan2(u, v);
if (H < 0.0f) H += rad360;
*h = (float)(H * 57.2957795131);
}
}
void imColorRGB2HSIbyte(unsigned char r, unsigned char g, unsigned char b, float *h, float *s, float *i)
{
float fr = imColorReconstruct(r, (imbyte)255);
float fg = imColorReconstruct(g, (imbyte)255);
float fb = imColorReconstruct(b, (imbyte)255);
imColorRGB2HSI(fr, fg, fb, h, s, i);
}
/**********************************/
/* HSI 2 RGB */
/**********************************/
void imColorHSI2RGB(float h, float s, float i, float *r, float *g, float *b)
{
static int first = 1;
static double _sqrt3;
double cosh, sinh, H, v, u;
if (first)
{
_sqrt3 = sqrt(3.0);
first = 0;
}
if (s == 0.0f || i == 1.0f || i == 0.0f || (int)h == 360)
{
*r = i;
*g = i;
*b = i;
return;
}
if (i < 0) i = 0;
if (i > 1) i = 1;
if (h > 360) h = (float)fmod(h, 360);
if (h < 0.0f) h += 360;
H = h / 57.2957795131;
cosh = cos(H);
sinh = sin(H);
{
float smax = imColorHSI_Smax((float)H, cosh, sinh, i);
if (s < 0) s = 0;
if (s > smax) s = smax;
}
v = s * cosh;
u = s * sinh * _sqrt3;
*r = (float)(i + v/1.5);
*g = (float)(i - (v - u)/3.0);
*b = (float)(i - (v + u)/3.0);
if (*r < 0) *r = -*r;
if (*g < 0) *g = -*g;
if (*b < 0) *b = -*b;
if (*r > 1) *r = 1.0f;
if (*g > 1) *g = 1.0f;
if (*b > 1) *b = 1.0f;
}
void imColorHSI2RGBbyte(float h, float s, float i, unsigned char *r, unsigned char *g, unsigned char *b)
{
float fr, fg, fb;
imColorHSI2RGB(h, s, i, &fr, &fg, &fb);
*r = imColorQuantize(fr, (imbyte)255);
*g = imColorQuantize(fg, (imbyte)255);
*b = imColorQuantize(fb, (imbyte)255);
}
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