[imager.git] / color.c

#include "image.h"
#include <math.h>

/*
=head1 NAME

color.c - color manipulation functions

=head1 SYNOPSIS

  i_fcolor color;
  i_rgb_to_hsvf(&color);
  i_hsv_to_rgbf(&color);

=head1 DESCRIPTION

A collection of utility functions for converting between color spaces.

*/

#define EPSILON (1e-8)

#define my_max(a, b) ((a) < (b) ? (b) : (a))
#define my_min(a, b) ((a) > (b) ? (b) : (a))

/*
=item i_rgb2hsvf(&color)

Converts the first 3 channels of color into hue, saturation and value.

Each value is scaled into the range 0 to 1.0.

=cut
*/
void i_rgb_to_hsvf(i_fcolor *color) {
  double h, s, v;
  double temp;
  double Cr, Cg, Cb;

  v = my_max(my_max(color->rgb.r, color->rgb.g), color->rgb.b);
  temp = my_min(my_min(color->rgb.r, color->rgb.g), color->rgb.b);
  if (v < EPSILON)
    s = 0;
  else
    s = (v-temp)/v;
  if (s == 0)
    h = 0;
  else {
    Cr = (v - color->rgb.r)/(v-temp);
    Cg = (v - color->rgb.g)/(v-temp);
    Cb = (v - color->rgb.b)/(v-temp);
    if (color->rgb.r == v)
      h = Cb - Cg;
    else if (color->rgb.g == v)
      h = 2 + Cr - Cb;
    else if (color->rgb.b == v)
      h = 4 + Cg - Cr;
    h = 60 * h;
    if (h < 0)
      h += 360;
  }
  color->channel[0] = h / 360.0;
  color->channel[1] = s;
  color->channel[2] = v;
}

/*
=item i_rgb2hsv(&color)

Converts the first 3 channels of color into hue, saturation and value.

Each value is scaled into the range 0 to 255.

=cut
*/
void i_rgb_to_hsv(i_color *color) {
  double h, s, v;
  double temp;
  double Cr, Cg, Cb;

  v = my_max(my_max(color->rgb.r, color->rgb.g), color->rgb.b);
  temp = my_min(my_min(color->rgb.r, color->rgb.g), color->rgb.b);
  if (v == 0)
    s = 0;
  else
    s = (v-temp)*255/v;
  if (s == 0)
    h = 0;
  else {
    Cr = (v - color->rgb.r)/(v-temp);
    Cg = (v - color->rgb.g)/(v-temp);
    Cb = (v - color->rgb.b)/(v-temp);
    if (color->rgb.r == v)
      h = Cb - Cg;
    else if (color->rgb.g == v)
      h = 2 + Cr - Cb;
    else if (color->rgb.b == v)
      h = 4 + Cg - Cr;
    h = h * 60.0;
    if (h < 0)
      h += 360;
  }
  color->channel[0] = h * 255 / 360.0;
  color->channel[1] = s;
  color->channel[2] = v;
}

/*
=item i_hsv_to_rgbf(&color)

Convert a HSV value to an RGB value, each value ranges from 0 to 1.

=cut
*/

void i_hsv_to_rgbf(i_fcolor *color) {
  double h = color->channel[0];
  double s = color->channel[1];
  double v = color->channel[2];

  if (color->channel[1] < EPSILON) {
    /* ignore h in this case */
    color->rgb.r = color->rgb.g = color->rgb.b = v;
  }
  else {
    int i;
    double f, m, n, k;
    h = fmod(h, 1.0) * 6;
    i = floor(h);
    f = h - i;
    m = v * (1 - s);
    n = v * (1 - s * f);
    k = v * (1 - s * (1 - f));
    switch (i) {
    case 0:
      color->rgb.r = v; color->rgb.g = k; color->rgb.b = m;
      break;
    case 1:
      color->rgb.r = n; color->rgb.g = v; color->rgb.b = m;
      break;
    case 2:
      color->rgb.r = m; color->rgb.g = v; color->rgb.b = k;
      break;
    case 3:
      color->rgb.r = m; color->rgb.g = n; color->rgb.b = v;
      break;
    case 4:
      color->rgb.r = k; color->rgb.g = m; color->rgb.b = v;
      break;
    case 5:
      color->rgb.r = v; color->rgb.g = m; color->rgb.b = n;
      break;
    }
  }
}

/*
=item i_hsv_to_rgb(&color)

Convert a HSV value to an RGB value, each value ranges from 0 to 1.

=cut
*/

void i_hsv_to_rgb(i_color *color) {
  double h = color->channel[0];
  double s = color->channel[1];
  double v = color->channel[2];

  if (color->channel[1] == 0) {
    /* ignore h in this case */
    color->rgb.r = color->rgb.g = color->rgb.b = v;
  }
  else {
    int i;
    double f;
    int m, n, k;
    h = h / 255.0 * 6;
    i = h;
    f = h - i;
    m = 0.5 + v * (255 - s) / 255;
    n = 0.5 + v * (255 - s * f) / 255;
    k = 0.5 + v * (255 - s * (1 - f)) / 255;
    switch (i) {
    case 0:
      color->rgb.r = v; color->rgb.g = k; color->rgb.b = m;
      break;
    case 1:
      color->rgb.r = n; color->rgb.g = v; color->rgb.b = m;
      break;
    case 2:
      color->rgb.r = m; color->rgb.g = v; color->rgb.b = k;
      break;
    case 3:
      color->rgb.r = m; color->rgb.g = n; color->rgb.b = v;
      break;
    case 4:
      color->rgb.r = k; color->rgb.g = m; color->rgb.b = v;
      break;
    case 5:
      color->rgb.r = v; color->rgb.g = m; color->rgb.b = n;
      break;
    }
  }
}

/*
=back

=head1 AUTHOR

Tony Cook <tony@develop-help.com>

=head1 SEE ALSO

Imager

=cut
*/
Commit	Line	Data
6607600c	1	#include "image.h"
efdc2568	2	#include <math.h>
6607600c TC	3
	4	/*
	5	=head1 NAME
	6
	7	color.c - color manipulation functions
	8
	9	=head1 SYNOPSIS
	10
	11	i_fcolor color;
	12	i_rgb_to_hsvf(&color);
	13	i_hsv_to_rgbf(&color);
	14
	15	=head1 DESCRIPTION
	16
	17	A collection of utility functions for converting between color spaces.
	18
	19	*/
	20
	21	#define EPSILON (1e-8)
	22
efdc2568 TC	23	#define my_max(a, b) ((a) < (b) ? (b) : (a))
	24	#define my_min(a, b) ((a) > (b) ? (b) : (a))
	25
6607600c TC	26	/*
	27	=item i_rgb2hsvf(&color)
	28
	29	Converts the first 3 channels of color into hue, saturation and value.
	30
	31	Each value is scaled into the range 0 to 1.0.
	32
	33	=cut
	34	*/
	35	void i_rgb_to_hsvf(i_fcolor *color) {
	36	double h, s, v;
	37	double temp;
	38	double Cr, Cg, Cb;
	39
efdc2568 TC	40	v = my_max(my_max(color->rgb.r, color->rgb.g), color->rgb.b);
efdc2568 TC	41	temp = my_min(my_min(color->rgb.r, color->rgb.g), color->rgb.b);
6607600c TC	42	if (v < EPSILON)
	43	s = 0;
	44	else
	45	s = (v-temp)/v;
	46	if (s == 0)
	47	h = 0;
	48	else {
	49	Cr = (v - color->rgb.r)/(v-temp);
	50	Cg = (v - color->rgb.g)/(v-temp);
	51	Cb = (v - color->rgb.b)/(v-temp);
	52	if (color->rgb.r == v)
	53	h = Cb - Cg;
	54	else if (color->rgb.g == v)
	55	h = 2 + Cr - Cb;
	56	else if (color->rgb.b == v)
	57	h = 4 + Cg - Cr;
	58	h = 60 * h;
	59	if (h < 0)
	60	h += 360;
	61	}
	62	color->channel[0] = h / 360.0;
	63	color->channel[1] = s;
	64	color->channel[2] = v;
	65	}
	66
efdc2568 TC	67	/*
	68	=item i_rgb2hsv(&color)
	69
	70	Converts the first 3 channels of color into hue, saturation and value.
	71
	72	Each value is scaled into the range 0 to 255.
	73
	74	=cut
	75	*/
	76	void i_rgb_to_hsv(i_color *color) {
	77	double h, s, v;
	78	double temp;
	79	double Cr, Cg, Cb;
	80
	81	v = my_max(my_max(color->rgb.r, color->rgb.g), color->rgb.b);
	82	temp = my_min(my_min(color->rgb.r, color->rgb.g), color->rgb.b);
	83	if (v == 0)
	84	s = 0;
	85	else
	86	s = (v-temp)*255/v;
	87	if (s == 0)
	88	h = 0;
	89	else {
	90	Cr = (v - color->rgb.r)/(v-temp);
	91	Cg = (v - color->rgb.g)/(v-temp);
	92	Cb = (v - color->rgb.b)/(v-temp);
	93	if (color->rgb.r == v)
	94	h = Cb - Cg;
	95	else if (color->rgb.g == v)
	96	h = 2 + Cr - Cb;
	97	else if (color->rgb.b == v)
	98	h = 4 + Cg - Cr;
	99	h = h * 60.0;
	100	if (h < 0)
	101	h += 360;
	102	}
	103	color->channel[0] = h * 255 / 360.0;
	104	color->channel[1] = s;
	105	color->channel[2] = v;
	106	}
	107
6607600c TC	108	/*
	109	=item i_hsv_to_rgbf(&color)
	110
	111	Convert a HSV value to an RGB value, each value ranges from 0 to 1.
	112
	113	=cut
	114	*/
	115
	116	void i_hsv_to_rgbf(i_fcolor *color) {
	117	double h = color->channel[0];
	118	double s = color->channel[1];
	119	double v = color->channel[2];
	120
	121	if (color->channel[1] < EPSILON) {
	122	/* ignore h in this case */
	123	color->rgb.r = color->rgb.g = color->rgb.b = v;
	124	}
	125	else {
	126	int i;
	127	double f, m, n, k;
	128	h = fmod(h, 1.0) * 6;
efdc2568	129	i = floor(h);
6607600c TC	130	f = h - i;
	131	m = v * (1 - s);
	132	n = v * (1 - s * f);
	133	k = v * (1 - s * (1 - f));
	134	switch (i) {
	135	case 0:
	136	color->rgb.r = v; color->rgb.g = k; color->rgb.b = m;
	137	break;
	138	case 1:
	139	color->rgb.r = n; color->rgb.g = v; color->rgb.b = m;
	140	break;
	141	case 2:
	142	color->rgb.r = m; color->rgb.g = v; color->rgb.b = k;
	143	break;
	144	case 3:
	145	color->rgb.r = m; color->rgb.g = n; color->rgb.b = v;
	146	break;
	147	case 4:
	148	color->rgb.r = k; color->rgb.g = m; color->rgb.b = v;
	149	break;
	150	case 5:
	151	color->rgb.r = v; color->rgb.g = m; color->rgb.b = n;
	152	break;
	153	}
	154	}
	155	}
	156
efdc2568 TC	157	/*
	158	=item i_hsv_to_rgb(&color)
	159
	160	Convert a HSV value to an RGB value, each value ranges from 0 to 1.
	161
	162	=cut
	163	*/
	164
	165	void i_hsv_to_rgb(i_color *color) {
	166	double h = color->channel[0];
	167	double s = color->channel[1];
	168	double v = color->channel[2];
	169
	170	if (color->channel[1] == 0) {
	171	/* ignore h in this case */
	172	color->rgb.r = color->rgb.g = color->rgb.b = v;
	173	}
	174	else {
	175	int i;
87039ee8 TC	176	double f;
87039ee8 TC	177	int m, n, k;
efdc2568 TC	178	h = h / 255.0 * 6;
	179	i = h;
	180	f = h - i;
87039ee8 TC	181	m = 0.5 + v * (255 - s) / 255;
	182	n = 0.5 + v * (255 - s * f) / 255;
	183	k = 0.5 + v * (255 - s * (1 - f)) / 255;
efdc2568 TC	184	switch (i) {
	185	case 0:
	186	color->rgb.r = v; color->rgb.g = k; color->rgb.b = m;
	187	break;
	188	case 1:
	189	color->rgb.r = n; color->rgb.g = v; color->rgb.b = m;
	190	break;
	191	case 2:
	192	color->rgb.r = m; color->rgb.g = v; color->rgb.b = k;
	193	break;
	194	case 3:
	195	color->rgb.r = m; color->rgb.g = n; color->rgb.b = v;
	196	break;
	197	case 4:
	198	color->rgb.r = k; color->rgb.g = m; color->rgb.b = v;
	199	break;
	200	case 5:
	201	color->rgb.r = v; color->rgb.g = m; color->rgb.b = n;
	202	break;
	203	}
	204	}
	205	}
	206
6607600c TC	207	/*
	208	=back
	209
	210	=head1 AUTHOR
	211
	212	Tony Cook <tony@develop-help.com>
	213
	214	=head1 SEE ALSO
	215
	216	Imager
	217
	218	=cut
	219	*/