gimp/app/core/gimpcoords.c

/* 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));
}

/*
 * Distance via manhattan metric, an upper bound for the eucledian metric.
 * used for e.g. bezier approximation
 */

gdouble
gimp_coords_manhattan_dist (const GimpCoords *a,
                            const GimpCoords *b)
{
  gdouble dist = 0;

  dist += fabs (a->pressure - b->pressure);
  dist += fabs (a->xtilt - b->xtilt);
  dist += fabs (a->ytilt - b->ytilt);
  dist += fabs (a->wheel - b->wheel);

  dist *= INPUT_RESOLUTION;

  dist += fabs (a->x - b->x);
  dist += fabs (a->y - b->y);

  return dist;
}

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);
}