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/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
* e-hsv-utils.c - utilites for manipulating colours in HSV space
* Copyright (C) 1995-2001 Seth Nickell, Peter Mattis, Spencer Kimball and Josh MacDonald
*
* Authors:
* Seth Nickell <seth@eazel.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License, version 2, as published by the Free Software Foundation.
*
* 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 Library 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 <config.h>
#include "e-hsv-utils.h"
/* tweak_hsv is a really tweaky function. it modifies its first argument, which
should be the colour you want tweaked. delta_h, delta_s and delta_v specify
how much you want their respective channels modified (and in what direction).
if it can't do the specified modification, it does it in the oppositon direction */
void
e_hsv_tweak (GdkColor *colour, gdouble delta_h, gdouble delta_s, gdouble delta_v)
{
gdouble h, s, v, r, g, b;
r = colour->red / 65535.0f;
g = colour->green / 65535.0f;
b = colour->blue / 65535.0f;
e_rgb_to_hsv (r, g, b, &h, &s, &v);
if (h + delta_h < 0) {
h -= delta_h;
} else {
h += delta_h;
}
if (s + delta_s < 0) {
s -= delta_s;
} else {
s += delta_s;
}
if (v + delta_v < 0) {
v -= delta_v;
} else {
v += delta_v;
}
e_hsv_to_rgb (h, s, v, &r, &g, &b);
colour->red = r * 65535.0f;
colour->green = g * 65535.0f;
colour->blue = b * 65535.0f;
}
/* Copy n' Paste code from the GTK+ colour selector (gtkcolorsel.c) */
/* Originally lifted, I suspect, from "Foley, van Dam" */
void
e_hsv_to_rgb (gdouble h, gdouble s, gdouble v,
gdouble *r, gdouble *g, gdouble *b)
{
gint i;
gdouble f, w, q, t;
if (s == 0.0)
s = 0.000001;
if (h == -1.0)
{
*r = v;
*g = v;
*b = v;
}
else
{
if (h == 360.0)
h = 0.0;
h = h / 60.0;
i = (gint) h;
f = h - i;
w = v * (1.0 - s);
q = v * (1.0 - (s * f));
t = v * (1.0 - (s * (1.0 - f)));
switch (i)
{
case 0:
*r = v;
*g = t;
*b = w;
break;
case 1:
*r = q;
*g = v;
*b = w;
break;
case 2:
*r = w;
*g = v;
*b = t;
break;
case 3:
*r = w;
*g = q;
*b = v;
break;
case 4:
*r = t;
*g = w;
*b = v;
break;
case 5:
*r = v;
*g = w;
*b = q;
break;
}
}
}
void
e_rgb_to_hsv (gdouble r, gdouble g, gdouble b,
gdouble *h, gdouble *s, gdouble *v)
{
double max, min, delta;
max = r;
if (g > max)
max = g;
if (b > max)
max = b;
min = r;
if (g < min)
min = g;
if (b < min)
min = b;
*v = max;
if (max != 0.0)
*s = (max - min) / max;
else
*s = 0.0;
if (*s == 0.0)
*h = -1.0;
else
{
delta = max - min;
if (r == max)
*h = (g - b) / delta;
else if (g == max)
*h = 2.0 + (b - r) / delta;
else if (b == max)
*h = 4.0 + (r - g) / delta;
*h = *h * 60.0;
if (*h < 0.0)
*h = *h + 360;
}
}
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