/* dzl-rgba.c
*
* Copyright (C) 2014 Christian Hergert <christian@hergert.me>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#define G_LOG_DOMAIN "dzl-rgba"
#include "config.h"
#include "dzl-rgba.h"
/*
* The following code is borrowed ultimately upstream through Clearlooks
* theme engine in 2.x days. It has been ported to use GdkRGBA. It exists
* all over the place, feel free to use this under any license compatible
* with upstream.
*/
/* Clearlooks - a cairo based GTK+ engine
* Copyright (C) 2006 Andrew Johnson <acjgenius@earthlink.net>
* Copyright (C) 2007 Benjamin Berg <benjamin@sipsolutions.net>
*
* 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 2.1 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
* Lesser 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
static void
rgb_to_hls (gdouble *r,
gdouble *g,
gdouble *b)
{
gdouble min;
gdouble max;
gdouble red;
gdouble green;
gdouble blue;
gdouble h, l, s;
gdouble delta;
red = *r;
green = *g;
blue = *b;
if (red > green)
{
if (red > blue)
max = red;
else
max = blue;
if (green < blue)
min = green;
else
min = blue;
}
else
{
if (green > blue)
max = green;
else
max = blue;
if (red < blue)
min = red;
else
min = blue;
}
l = (max + min) / 2;
s = 0;
h = 0;
if (max != min)
{
if (l <= 0.5)
s = (max - min) / (max + min);
else
s = (max - min) / (2 - max - min);
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 *= 60;
if (h < 0.0)
h += 360;
}
*r = h;
*g = l;
*b = s;
}
static void
hls_to_rgb (gdouble *h,
gdouble *l,
gdouble *s)
{
gdouble hue;
gdouble lightness;
gdouble saturation;
gdouble m1, m2;
gdouble r, g, b;
lightness = *l;
saturation = *s;
if (lightness <= 0.5)
m2 = lightness * (1 + saturation);
else
m2 = lightness + saturation - lightness * saturation;
m1 = 2 * lightness - m2;
if (saturation == 0)
{
*h = lightness;
*l = lightness;
*s = lightness;
}
else
{
hue = *h + 120;
while (hue > 360)
hue -= 360;
while (hue < 0)
hue += 360;
if (hue < 60)
r = m1 + (m2 - m1) * hue / 60;
else if (hue < 180)
r = m2;
else if (hue < 240)
r = m1 + (m2 - m1) * (240 - hue) / 60;
else
r = m1;
hue = *h;
while (hue > 360)
hue -= 360;
while (hue < 0)
hue += 360;
if (hue < 60)
g = m1 + (m2 - m1) * hue / 60;
else if (hue < 180)
g = m2;
else if (hue < 240)
g = m1 + (m2 - m1) * (240 - hue) / 60;
else
g = m1;
hue = *h - 120;
while (hue > 360)
hue -= 360;
while (hue < 0)
hue += 360;
if (hue < 60)
b = m1 + (m2 - m1) * hue / 60;
else if (hue < 180)
b = m2;
else if (hue < 240)
b = m1 + (m2 - m1) * (240 - hue) / 60;
else
b = m1;
*h = r;
*l = g;
*s = b;
}
}
void
dzl_rgba_shade (const GdkRGBA *rgba,
GdkRGBA *dst,
gdouble k)
{
gdouble red;
gdouble green;
gdouble blue;
red = rgba->red;
green = rgba->green;
blue = rgba->blue;
rgb_to_hls (&red, &green, &blue);
green *= k;
if (green > 1.0)
green = 1.0;
else if (green < 0.0)
green = 0.0;
blue *= k;
if (blue > 1.0)
blue = 1.0;
else if (blue < 0.0)
blue = 0.0;
hls_to_rgb (&red, &green, &blue);
dst->red = red;
dst->green = green;
dst->blue = blue;
dst->alpha = rgba->alpha;
}