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gimp/libgimp/gimpcolorspace.c

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/* LIBGIMP - The GIMP Library
* Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include <glib.h>
#include "gimpcolorspace.h"
/*********************************
* color conversion routines *
*********************************/
void
gimp_rgb_to_hsv (gint *red,
gint *green,
gint *blue)
{
gint r, g, b;
gdouble h, s, v;
gint min, max;
gint delta;
h = 0.0;
r = *red;
g = *green;
b = *blue;
if (r > g)
{
max = MAX (r, b);
min = MIN (g, b);
}
else
{
max = MAX (g, b);
min = MIN (r, b);
}
v = max;
if (max != 0)
s = ((max - min) * 255) / (gdouble) max;
else
s = 0;
if (s == 0)
h = 0;
else
{
delta = max - min;
if (r == max)
h = (g - b) / (gdouble) delta;
else if (g == max)
h = 2 + (b - r) / (gdouble) delta;
else if (b == max)
h = 4 + (r - g) / (gdouble) delta;
h *= 42.5;
if (h < 0)
h += 255;
if (h > 255)
h -= 255;
}
*red = h;
*green = s;
*blue = v;
}
void
gimp_hsv_to_rgb (gint *hue,
gint *saturation,
gint *value)
{
gdouble h, s, v;
gdouble f, p, q, t;
if (*saturation == 0)
{
*hue = *value;
*saturation = *value;
*value = *value;
}
else
{
h = *hue * 6.0 / 255.0;
s = *saturation / 255.0;
v = *value / 255.0;
f = h - (gint) h;
p = v * (1.0 - s);
q = v * (1.0 - (s * f));
t = v * (1.0 - (s * (1.0 - f)));
switch ((gint) h)
{
case 0:
*hue = v * 255;
*saturation = t * 255;
*value = p * 255;
break;
case 1:
*hue = q * 255;
*saturation = v * 255;
*value = p * 255;
break;
case 2:
*hue = p * 255;
*saturation = v * 255;
*value = t * 255;
break;
case 3:
*hue = p * 255;
*saturation = q * 255;
*value = v * 255;
break;
case 4:
*hue = t * 255;
*saturation = p * 255;
*value = v * 255;
break;
case 5:
*hue = v * 255;
*saturation = p * 255;
*value = q * 255;
break;
}
}
}
void
gimp_rgb_to_hls (gint *red,
gint *green,
gint *blue)
{
gint r, g, b;
gdouble h, l, s;
gint min, max;
gint delta;
r = *red;
g = *green;
b = *blue;
if (r > g)
{
max = MAX (r, b);
min = MIN (g, b);
}
else
{
max = MAX (g, b);
min = MIN (r, b);
}
l = (max + min) / 2.0;
if (max == min)
{
s = 0.0;
h = 0.0;
}
else
{
delta = (max - min);
if (l < 128)
s = 255 * (gdouble) delta / (gdouble) (max + min);
else
s = 255 * (gdouble) delta / (gdouble) (511 - max - min);
if (r == max)
h = (g - b) / (gdouble) delta;
else if (g == max)
h = 2 + (b - r) / (gdouble) delta;
else
h = 4 + (r - g) / (gdouble) delta;
h = h * 42.5;
if (h < 0)
h += 255;
else if (h > 255)
h -= 255;
}
*red = h;
*green = l;
*blue = s;
}
gint
gimp_rgb_to_l (gint red,
gint green,
gint blue)
{
gint min, max;
if (red > green)
{
max = MAX (red, blue);
min = MIN (green, blue);
}
else
{
max = MAX (green, blue);
min = MIN (red, blue);
}
return (max + min) / 2.0;
}
static gint
gimp_hls_value (gdouble n1,
gdouble n2,
gdouble hue)
{
gdouble value;
if (hue > 255)
hue -= 255;
else if (hue < 0)
hue += 255;
if (hue < 42.5)
value = n1 + (n2 - n1) * (hue / 42.5);
else if (hue < 127.5)
value = n2;
else if (hue < 170)
value = n1 + (n2 - n1) * ((170 - hue) / 42.5);
else
value = n1;
return (gint) (value * 255);
}
void
gimp_hls_to_rgb (gint *hue,
gint *lightness,
gint *saturation)
{
gdouble h, l, s;
gdouble m1, m2;
h = *hue;
l = *lightness;
s = *saturation;
if (s == 0)
{
/* achromatic case */
*hue = l;
*lightness = l;
*saturation = l;
}
else
{
if (l < 128)
m2 = (l * (255 + s)) / 65025.0;
else
m2 = (l + s - (l * s) / 255.0) / 255.0;
m1 = (l / 127.5) - m2;
/* chromatic case */
*hue = gimp_hls_value (m1, m2, h + 85);
*lightness = gimp_hls_value (m1, m2, h);
*saturation = gimp_hls_value (m1, m2, h - 85);
}
}
void
gimp_rgb_to_hsv_double (gdouble *red,
gdouble *green,
gdouble *blue)
{
gdouble r, g, b;
gdouble h, s, v;
gdouble min, max;
gdouble delta;
r = *red;
g = *green;
b = *blue;
h = 0.0; /* Shut up -Wall */
if (r > g)
{
max = MAX (r, b);
min = MIN (g, b);
}
else
{
max = MAX (g, b);
min = MIN (r, b);
}
v = max;
if (max != 0.0)
s = (max - min) / max;
else
s = 0.0;
if (s == 0.0)
{
h = 0.0;
}
else
{
delta = max - min;
if (r == max)
h = (g - b) / delta;
else if (g == max)
h = 2 + (b - r) / delta;
else if (b == max)
h = 4 + (r - g) / delta;
h /= 6.0;
if (h < 0.0)
h += 1.0;
else if (h > 1.0)
h -= 1.0;
}
*red = h;
*green = s;
*blue = v;
}
void
gimp_hsv_to_rgb_double (gdouble *hue,
gdouble *saturation,
gdouble *value)
{
gdouble h, s, v;
gdouble f, p, q, t;
if (*saturation == 0.0)
{
*hue = *value;
*saturation = *value;
*value = *value;
}
else
{
h = *hue * 6.0;
s = *saturation;
v = *value;
if (h == 6.0)
h = 0.0;
f = h - (gint) h;
p = v * (1.0 - s);
q = v * (1.0 - s * f);
t = v * (1.0 - s * (1.0 - f));
switch ((gint) h)
{
case 0:
*hue = v;
*saturation = t;
*value = p;
break;
case 1:
*hue = q;
*saturation = v;
*value = p;
break;
case 2:
*hue = p;
*saturation = v;
*value = t;
break;
case 3:
*hue = p;
*saturation = q;
*value = v;
break;
case 4:
*hue = t;
*saturation = p;
*value = v;
break;
case 5:
*hue = v;
*saturation = p;
*value = q;
break;
}
}
}
void
gimp_rgb_to_hsv4 (guchar *rgb,
gdouble *hue,
gdouble *saturation,
gdouble *value)
{
gdouble red, green, blue;
gdouble h, s, v;
gdouble min, max;
gdouble delta;
red = rgb[0] / 255.0;
green = rgb[1] / 255.0;
blue = rgb[2] / 255.0;
h = 0.0; /* Shut up -Wall */
if (red > green)
{
max = MAX (red, blue);
min = MIN (green, blue);
}
else
{
max = MAX (green, blue);
min = MIN (red, blue);
}
v = max;
if (max != 0.0)
s = (max - min) / max;
else
s = 0.0;
if (s == 0.0)
h = 0.0;
else
{
delta = max - min;
if (red == max)
h = (green - blue) / delta;
else if (green == max)
h = 2 + (blue - red) / delta;
else if (blue == max)
h = 4 + (red - green) / delta;
h /= 6.0;
if (h < 0.0)
h += 1.0;
else if (h > 1.0)
h -= 1.0;
}
*hue = h;
*saturation = s;
*value = v;
}
void
gimp_hsv_to_rgb4 (guchar *rgb,
gdouble hue,
gdouble saturation,
gdouble value)
{
gdouble h, s, v;
gdouble f, p, q, t;
if (saturation == 0.0)
{
hue = value;
saturation = value;
value = value;
}
else
{
h = hue * 6.0;
s = saturation;
v = value;
if (h == 6.0)
h = 0.0;
f = h - (gint) h;
p = v * (1.0 - s);
q = v * (1.0 - s * f);
t = v * (1.0 - s * (1.0 - f));
switch ((int) h)
{
case 0:
hue = v;
saturation = t;
value = p;
break;
case 1:
hue = q;
saturation = v;
value = p;
break;
case 2:
hue = p;
saturation = v;
value = t;
break;
case 3:
hue = p;
saturation = q;
value = v;
break;
case 4:
hue = t;
saturation = p;
value = v;
break;
case 5:
hue = v;
saturation = p;
value = q;
break;
}
}
rgb[0] = hue * 255;
rgb[1] = saturation * 255;
rgb[2] = value * 255;
}
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