gimp/app/core/gimpcurve-map.c

/* GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * 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 "libgimpmath/gimpmath.h"

#include "core-types.h"

#include "gimpcurve.h"
#include "gimpcurve-map.h"


gdouble
gimp_curve_map_value (GimpCurve *curve,
                      gdouble    value)
{
  g_return_val_if_fail (GIMP_IS_CURVE (curve), 0.0);

  if (curve->identity)
    {
      return value;
    }

  if (value < 0.0)
    {
      return curve->samples[0];
    }
  else if (value >= 1.0)
    {
      return curve->samples[curve->n_samples - 1];
    }
  else  /* interpolate the curve */
    {
      gint    index = floor (value * (gdouble) (curve->n_samples - 1));
      gdouble f     = value * (gdouble) (curve->n_samples - 1) - index;

      return (1.0 - f) * curve->samples[index] + f  * curve->samples[index + 1];
    }
}

void
gimp_curve_map_pixels (GimpCurve *curve_all,
                       GimpCurve *curve_red,
                       GimpCurve *curve_green,
                       GimpCurve *curve_blue,
                       GimpCurve *curve_alpha,
                       gfloat    *src,
                       gfloat    *dest,
                       glong      samples)
{
  g_return_if_fail (GIMP_IS_CURVE (curve_all));
  g_return_if_fail (GIMP_IS_CURVE (curve_red));
  g_return_if_fail (GIMP_IS_CURVE (curve_green));
  g_return_if_fail (GIMP_IS_CURVE (curve_blue));
  g_return_if_fail (GIMP_IS_CURVE (curve_alpha));

  while (samples--)
    {
      dest[0] = gimp_curve_map_value (curve_all,
                                      gimp_curve_map_value (curve_red,
                                                            src[0]));
      dest[1] = gimp_curve_map_value (curve_all,
                                      gimp_curve_map_value (curve_green,
                                                            src[1]));
      dest[2] = gimp_curve_map_value (curve_all,
                                      gimp_curve_map_value (curve_blue,
                                                            src[2]));
      /* don't apply the overall curve to the alpha channel */
      dest[3] = gimp_curve_map_value (curve_alpha, src[3]);

      src  += 4;
      dest += 4;
    }
}