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/* The GIMP -- an image manipulation program
* Copyright (C) 1995 Spencer Kimball and Peter Mattis
*
* gimpcoords.c
* Copyright (C) 2002 Simon Budig <simon@gimp.org>
*
* 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 2 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include "config.h"
#include <glib-object.h>
#include "core-types.h"
#include "gimpcoords.h"
#define INPUT_RESOLUTION 256
/* amul * a + bmul * b = ret_val */
void
gimp_coords_mix (const gdouble amul,
const GimpCoords *a,
const gdouble bmul,
const GimpCoords *b,
GimpCoords *ret_val)
{
if (b)
{
ret_val->x = amul * a->x + bmul * b->x ;
ret_val->y = amul * a->y + bmul * b->y ;
ret_val->pressure = amul * a->pressure + bmul * b->pressure ;
ret_val->xtilt = amul * a->xtilt + bmul * b->xtilt ;
ret_val->ytilt = amul * a->ytilt + bmul * b->ytilt ;
ret_val->wheel = amul * a->wheel + bmul * b->wheel ;
}
else
{
ret_val->x = amul * a->x;
ret_val->y = amul * a->y;
ret_val->pressure = amul * a->pressure;
ret_val->xtilt = amul * a->xtilt;
ret_val->ytilt = amul * a->ytilt;
ret_val->wheel = amul * a->wheel;
}
}
/* (a+b)/2 = ret_average */
void
gimp_coords_average (const GimpCoords *a,
const GimpCoords *b,
GimpCoords *ret_average)
{
gimp_coords_mix (0.5, a, 0.5, b, ret_average);
}
/* a + b = ret_add */
void
gimp_coords_add (const GimpCoords *a,
const GimpCoords *b,
GimpCoords *ret_add)
{
gimp_coords_mix (1.0, a, 1.0, b, ret_add);
}
/* a - b = ret_difference */
void
gimp_coords_difference (const GimpCoords *a,
const GimpCoords *b,
GimpCoords *ret_difference)
{
gimp_coords_mix (1.0, a, -1.0, b, ret_difference);
}
/* a * f = ret_product */
void
gimp_coords_scale (const gdouble f,
const GimpCoords *a,
GimpCoords *ret_product)
{
gimp_coords_mix (f, a, 0.0, NULL, ret_product);
}
/* local helper for measuring the scalarproduct of two gimpcoords. */
gdouble
gimp_coords_scalarprod (const GimpCoords *a,
const GimpCoords *b)
{
return (a->x * b->x +
a->y * b->y +
a->pressure * b->pressure +
a->xtilt * b->xtilt +
a->ytilt * b->ytilt +
a->wheel * b->wheel );
}
/*
* The "lenght" of the gimpcoord.
* Applies a metric that increases the weight on the
* pressure/xtilt/ytilt/wheel to ensure proper interpolation
*/
gdouble
gimp_coords_length_squared (const GimpCoords *a)
{
GimpCoords upscaled_a;
upscaled_a.x = a->x;
upscaled_a.y = a->y;
upscaled_a.pressure = a->pressure * INPUT_RESOLUTION;
upscaled_a.xtilt = a->xtilt * INPUT_RESOLUTION;
upscaled_a.ytilt = a->ytilt * INPUT_RESOLUTION;
upscaled_a.wheel = a->wheel * INPUT_RESOLUTION;
return gimp_coords_scalarprod (&upscaled_a, &upscaled_a);
}
gdouble
gimp_coords_length (const GimpCoords *a)
{
return sqrt (gimp_coords_length_squared (a));
}
gboolean
gimp_coords_equal (const GimpCoords *a,
const GimpCoords *b)
{
return ( a->x == b->x &&
a->y == b->y &&
a->pressure == b->pressure &&
a->xtilt == b->xtilt &&
a->ytilt == b->ytilt &&
a->wheel == b->wheel);
}
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