OpenBK7231T_App/src/rgb2hsv.c

// Copyright (c) 2014, Jan Winkler <winkler@cs.uni-bremen.de>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
//     * Neither the name of Universität Bremen nor the names of its
//       contributors may be used to endorse or promote products derived from
//       this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

/* Author: Jan Winkler */

#include <math.h>


static float my_min(float a, float b){
	if(a>b)
		return b;
	return a;
}	
static float my_max(float a, float b){
	if(a>b)
		return a;
	return b;
}
/*! \brief Convert RGB to HSV color space
  
  Converts a given set of RGB values `r', `g', `b' into HSV
  coordinates. The input RGB values are in the range [0, 1], and the
  output HSV values are in the ranges h = [0, 360], and s, v = [0,
  1], respectively.
  
  \param fR Red component, used as input, range: [0, 1]
  \param fG Green component, used as input, range: [0, 1]
  \param fB Blue component, used as input, range: [0, 1]
  \param fH Hue component, used as output, range: [0, 360]
  \param fS Hue component, used as output, range: [0, 1]
  \param fV Hue component, used as output, range: [0, 1]
  
*/
void RGBtoHSV(float fR, float fG, float fB, float *ofH, float *ofS, float *ofV) {
	float fH, fS, fV;
	float fCMax;
	float fCMin;
	float fDelta;

	fCMax = my_max(my_max(fR, fG), fB);
	fCMin = my_min(my_min(fR, fG), fB);
	fDelta = fCMax - fCMin;

	if(fDelta > 0) {
		if(fCMax == fR) {
			fH = 60 * (fmod(((fG - fB) / fDelta), 6));
		} else if(fCMax == fG) {
			fH = 60 * (((fB - fR) / fDelta) + 2);
		} else if(fCMax == fB) {
			fH = 60 * (((fR - fG) / fDelta) + 4);
		} else {
			fH = 0;
		}

		if(fCMax > 0) {
			fS = fDelta / fCMax;
		} else {
			fS = 0;
		}

		fV = fCMax;
	} else {
		fH = 0;
		fS = 0;
		fV = fCMax;
	}

	if(fH < 0) {
		fH = 360 + fH;
	}
	*ofH = fH;
	*ofS = fS;
	*ofV = fV;
}

/*! \brief Convert HSV to RGB color space
  
  Converts a given set of HSV values `h', `s', `v' into RGB
  coordinates. The output RGB values are in the range [0, 1], and
  the input HSV values are in the ranges h = [0, 360], and s, v =
  [0, 1], respectively.
  
  \param fR Red component, used as output, range: [0, 1]
  \param fG Green component, used as output, range: [0, 1]
  \param fB Blue component, used as output, range: [0, 1]
  \param fH Hue component, used as input, range: [0, 360]
  \param fS Hue component, used as input, range: [0, 1]
  \param fV Hue component, used as input, range: [0, 1]
  
*/
void HSVtoRGB(float *ofR, float *ofG, float *ofB, float fH, float fS, float fV) {
	float fC;
	float fHPrime;
	float fX;
	float fM;
	float fR, fG, fB;

	fC = fV * fS; // Chroma
	fHPrime = fmod(fH / 60.0, 6);
	fX = fC * (1 - fabs(fmod(fHPrime, 2) - 1));
	fM = fV - fC;

	if(0 <= fHPrime && fHPrime < 1) {
		fR = fC;
		fG = fX;
		fB = 0;
	} else if(1 <= fHPrime && fHPrime < 2) {
		fR = fX;
		fG = fC;
		fB = 0;
	} else if(2 <= fHPrime && fHPrime < 3) {
		fR = 0;
		fG = fC;
		fB = fX;
	} else if(3 <= fHPrime && fHPrime < 4) {
		fR = 0;
		fG = fX;
		fB = fC;
	} else if(4 <= fHPrime && fHPrime < 5) {
		fR = fX;
		fG = 0;
		fB = fC;
	} else if(5 <= fHPrime && fHPrime < 6) {
		fR = fC;
		fG = 0;
		fB = fX;
	} else {
		fR = 0;
		fG = 0;
		fB = 0;
	}

	fR += fM;
	fG += fM;
	fB += fM;

	*ofR = fR;
	*ofG = fG;
	*ofB = fB;
}