image-colours/colours.c

#include "colours.h"

#include <tgmath.h>

struct ColourRGB CMYKtoRGB(struct ColourCMYK cmyk)
{
	struct ColourRGB result;

	result.r = (1.0 - cmyk.c) * (1.0 - cmyk.k);
	result.g = (1.0 - cmyk.m) * (1.0 - cmyk.k);
	result.b = (1.0 - cmyk.y) * (1.0 - cmyk.k);

	return result;
}

struct ColourRGB HSVtoRGB(struct ColourHSV hsv)
{
	struct ColourRGB result;
	double c;
	double x;
	double m;

	c = hsv.s * hsv.v;
	x = c * (1.0 - fabs(fmod(hsv.h / 60.0, 2) - 1.0));
	m = hsv.v - c;

	int angle = hsv.h / 60;
	switch (angle)
	{
	// 0 - 60
	case 6:
	case 0:
		result.r = c;
		result.g = x;
		result.b = 0;
		break;
	// 60 - 120
	case 1:
		result.r = x;
		result.g = c;
		result.b = 0;
		break;
	// 120 - 180
	case 2:
		result.r = 0;
		result.g = c;
		result.b = x;
		break;
	// 180 - 240
	case 3:
		result.r = 0;
		result.g = x;
		result.b = c;
		break;
	// 240 - 300
	case 4:
		result.r = x;
		result.g = 0;
		result.b = c;
		break;
	// 300 - 360
	case 5:
		result.r = c;
		result.g = 0;
		result.b = x;
		break;
	// Should never happen
	default:
		result.r = 0;
		result.g = 0;
		result.b = 0;
		break;
	}

	result.r += m;
	result.g += m;
	result.b += m;

	return result;
}

struct ColourRGB HSLtoRGB(struct ColourHSL hsl)
{
	struct ColourRGB result;
	double c;
	double x;
	double m;

	c = hsl.s * (1.0 - fabs(2 * hsl.l - 1));
	x = c * (1.0 - fabs(fmod(hsl.h / 60.0, 2) - 1.0));
	m = hsl.l - c/2;

	int angle = hsl.h / 60;
	switch (angle)
	{
	// 0 - 60
	case 6:
	case 0:
		result.r = c;
		result.g = x;
		result.b = 0;
		break;
	// 60 - 120
	case 1:
		result.r = x;
		result.g = c;
		result.b = 0;
		break;
	// 120 - 180
	case 2:
		result.r = 0;
		result.g = c;
		result.b = x;
		break;
	// 180 - 240
	case 3:
		result.r = 0;
		result.g = x;
		result.b = c;
		break;
	// 240 - 300
	case 4:
		result.r = x;
		result.g = 0;
		result.b = c;
		break;
	// 300 - 360
	case 5:
		result.r = c;
		result.g = 0;
		result.b = x;
		break;
	// Should never happen
	default:
		result.r = 0;
		result.g = 0;
		result.b = 0;
		break;
	}

	result.r += m;
	result.g += m;
	result.b += m;

	return result;
}

struct ColourCMYK RGBtoCMYK(struct ColourRGB rgb)
{
	struct ColourCMYK result;

	// max(r,g,b)
	result.k = rgb.r > rgb.g ? rgb.r : rgb.g;
	result.k = rgb.b > result.k ? rgb.b : result.k;
	result.k = 1.0 - result.k;

	if (1.0 == result.k)
	{
		result.c = 0;
		result.m = 0;
		result.y = 0;
	}
	else
	{
		result.c = (1.0 - rgb.r - result.k) / (1.0 - result.k);
		result.m = (1.0 - rgb.g - result.k) / (1.0 - result.k);
		result.y = (1.0 - rgb.b - result.k) / (1.0 - result.k);
	}

	return result;
}

struct ColourCMYK HSVtoCMYK(struct ColourHSV hsv)
{
	struct ColourCMYK result;

	result = RGBtoCMYK(HSVtoRGB(hsv));

	return result;
}

struct ColourCMYK HSLtoCMYK(struct ColourHSL hsl)
{
	struct ColourCMYK result;

	result = RGBtoCMYK(HSLtoRGB(hsl));

	return result;
}

struct ColourHSV RGBtoHSV(struct ColourRGB rgb)
{
	struct ColourHSV result;

	double c_max;
	double c_min;
	double delta;

	// max(r,g,b)
	c_max = rgb.r > rgb.g ? rgb.r : rgb.g;
	c_max = rgb.b > c_max ? rgb.b : c_max;

	// min(r,g,b)
	c_min = rgb.r < rgb.g ? rgb.r : rgb.g;
	c_min = rgb.b < c_min ? rgb.b : c_min;

	delta = c_max - c_min;

	if (delta > 0)
	{
		if (c_max == rgb.r)
		{
			result.h = 60 * fmod((rgb.g - rgb.b) / delta, 6);
		}
		else if (c_max == rgb.g)
		{
			result.h = 60 * ((rgb.b - rgb.r) / delta + 2);
		}
		else
		{
			result.h = 60 * ((rgb.r - rgb.g) / delta + 4);
		}

		result.v = c_max;
		result.s = delta / result.v;
	}
	else
	{
		result.h = 0;
		result.s = 0;
		result.v = c_max;
	}

	if (result.h < 0)
	{
		result.h += 360;
	}

	return result;
}

struct ColourHSV CMYKtoHSV(struct ColourCMYK cmyk)
{
	struct ColourHSV result;

	result = RGBtoHSV(CMYKtoRGB(cmyk));

	return result;
}

struct ColourHSV HSLtoHSV(struct ColourHSL hsl)
{
	struct ColourHSV result;

	result = RGBtoHSV(HSLtoRGB(hsl));

	return result;
}

struct ColourHSL RGBtoHSL(struct ColourRGB rgb)
{
	struct ColourHSL result;

	double c_max;
	double c_min;
	double delta;

	// max(r,g,b)
	c_max = rgb.r > rgb.g ? rgb.r : rgb.g;
	c_max = rgb.b > c_max ? rgb.b : c_max;

	// min(r,g,b)
	c_min = rgb.r < rgb.g ? rgb.r : rgb.g;
	c_min = rgb.b < c_min ? rgb.b : c_min;

	delta = c_max - c_min;

	if (delta > 0)
	{
		if (c_max == rgb.r)
		{
			result.h = 60 * fmod((rgb.g - rgb.b) / delta, 6);
		}
		else if (c_max == rgb.g)
		{
			result.h = 60 * ((rgb.b - rgb.r) / delta + 2);
		}
		else
		{
			result.h = 60 * ((rgb.r - rgb.g) / delta + 4);
		}

		result.l = (c_max + c_min) / 2;
		result.s = delta / (1.0 - fabs(2 * result.l - 1.0));
	}
	else
	{
		result.h = 0;
		result.s = 0;
		result.l = (c_max + c_min) / 2;
	}

	if (result.h < 0)
	{
		result.h += 360;
	}

	return result;
}

struct ColourHSL CMYKtoHSL(struct ColourCMYK cmyk)
{
	struct ColourHSL result;

	result = RGBtoHSL(CMYKtoRGB(cmyk));

	return result;
}

struct ColourHSL HSVtoHSL(struct ColourHSV hsv)
{
	struct ColourHSL result;

	result = RGBtoHSL(HSVtoRGB(hsv));

	return result;
}