gimp/app/base/lut-funcs.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 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/>.
 */

#include "config.h"

#include <glib-object.h>

#include "libgimpmath/gimpmath.h"

#include "base-types.h"

#include "gimphistogram.h"
#include "gimplut.h"
#include "lut-funcs.h"


/* ---------- Brightness/Contrast -----------*/

typedef struct
{
  gdouble brightness;
  gdouble contrast;
} BrightnessContrastLutData;

static gfloat
brightness_contrast_lut_func (BrightnessContrastLutData *data,
                              gint                       nchannels,
                              gint                       channel,
                              gfloat                     value)
{
  gdouble slant;

  /* return the original value for the alpha channel */
  if ((nchannels == 2 || nchannels == 4) && channel == nchannels -1)
    return value;

  /* apply brightness */
  if (data->brightness < 0.0)
    value = value * (1.0 + data->brightness);
  else
    value = value + ((1.0 - value) * data->brightness);

  slant = tan ((data->contrast + 1) * G_PI_4);
  value = (value - 0.5) * slant + 0.5;

  return value;
}

void
brightness_contrast_lut_setup (GimpLut *lut,
                               gdouble  brightness,
                               gdouble  contrast,
                               gint     n_channels)
{
  BrightnessContrastLutData data;

  g_return_if_fail (lut != NULL);

  data.brightness = brightness;
  data.contrast   = contrast;

  gimp_lut_setup (lut,
                  (GimpLutFunc) brightness_contrast_lut_func, &data, n_channels);
}

GimpLut *
brightness_contrast_lut_new (gdouble brightness,
                             gdouble contrast,
                             gint    n_channels)
{
  GimpLut *lut = gimp_lut_new ();

  brightness_contrast_lut_setup (lut, brightness, contrast, n_channels);

  return lut;
}

/* ---------------- invert ------------------ */

static gfloat
invert_lut_func (gpointer  unused,
                 gint      n_channels,
                 gint      channel,
                 gfloat    value)
{
  /* don't invert the alpha channel */
  if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
    return value;

  return 1.0 - value;
}

static void
invert_lut_setup (GimpLut *lut,
                  gint     n_channels)
{
  g_return_if_fail (lut != NULL);

  gimp_lut_setup_exact (lut, (GimpLutFunc) invert_lut_func, NULL, n_channels);
}

GimpLut *
invert_lut_new (gint n_channels)
{
  GimpLut *lut = gimp_lut_new ();

  invert_lut_setup (lut, n_channels);

  return lut;
}

/* ---------------- add (or subract)------------------ */

static gfloat
add_lut_func (gdouble *amount,
              gint     n_channels,
              gint     channel,
              gfloat   value)
{
  /* don't change the alpha channel */
  if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
    return value;

  return (value + *amount);
}

static void
add_lut_setup (GimpLut *lut,
               gdouble  amount,
               gint     n_channels)
{
  g_return_if_fail (lut != NULL);

  gimp_lut_setup (lut, (GimpLutFunc) add_lut_func, &amount, n_channels);
}

GimpLut *
add_lut_new (gdouble amount,
             gint    n_channels)
{
  GimpLut *lut = gimp_lut_new ();

  add_lut_setup (lut, amount, n_channels);

  return lut;
}

/* ---------------- intersect (MIN (pixel, value)) ------------------ */

static gfloat
intersect_lut_func (gdouble *min,
                    gint     n_channels,
                    gint     channel,
                    gfloat   value)
{
  /* don't change the alpha channel */
  if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
    return value;

  return MIN (value, *min);
}

static void
intersect_lut_setup (GimpLut *lut,
                     gdouble  value,
                     gint     n_channels)
{
  g_return_if_fail (lut != NULL);

  gimp_lut_setup_exact (lut,
                        (GimpLutFunc) intersect_lut_func, &value, n_channels);
}

GimpLut *
intersect_lut_new (gdouble value,
                   gint    n_channels)
{
  GimpLut *lut = gimp_lut_new ();

  intersect_lut_setup (lut, value, n_channels);

  return lut;
}

/* ---------------- Threshold ------------------ */

static gfloat
threshold_lut_func (gdouble *min,
                    gint     n_channels,
                    gint     channel,
                    gfloat   value)
{
  /* don't change the alpha channel */
  if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
    return value;

  if (value < *min)
    return 0.0;

  return 1.0;
}

static void
threshold_lut_setup (GimpLut *lut,
                     gdouble  value,
                     gint     n_channels)
{
  g_return_if_fail (lut != NULL);

  gimp_lut_setup_exact (lut,
                        (GimpLutFunc) threshold_lut_func, &value, n_channels);
}

GimpLut *
threshold_lut_new (gdouble value,
                   gint    n_channels)
{
  GimpLut *lut = gimp_lut_new ();

  threshold_lut_setup (lut, value, n_channels);

  return lut;
}

/* --------------- posterize ---------------- */

static gfloat
posterize_lut_func (gint   *ilevels,
                    gint    n_channels,
                    gint    channel,
                    gfloat  value)
{
  gint levels;

  /* don't posterize the alpha channel */
  if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
    return value;

  if (*ilevels < 2)
    levels = 2;
  else
    levels = *ilevels;

  value = RINT (value * (levels - 1.0)) / (levels - 1.0);

  return value;
}

void
posterize_lut_setup (GimpLut *lut,
                     gint     levels,
                     gint     n_channels)
{
  g_return_if_fail (lut != NULL);

  gimp_lut_setup_exact (lut,
                        (GimpLutFunc) posterize_lut_func, &levels, n_channels);
}

GimpLut *
posterize_lut_new (gint levels,
                   gint n_channels)
{
  GimpLut *lut = gimp_lut_new ();

  posterize_lut_setup (lut, levels, n_channels);

  return lut;
}

/* --------------- equalize ------------- */

typedef struct
{
  GimpHistogram *histogram;
  gint           part[5][257];
} hist_lut_struct;

static gfloat
equalize_lut_func (hist_lut_struct *hlut,
                   gint             nchannels,
                   gint             channel,
                   gfloat           value)
{
  gint i = 0;
  gint j;

  /* don't equalize the alpha channel */
  if ((nchannels == 2 || nchannels == 4) && channel == nchannels - 1)
    return value;

  j = (gint) (value * 255.0 + 0.5);

  while (hlut->part[channel][i + 1] <= j)
    i++;

  return i / 255.0;
}

static void
equalize_lut_setup (GimpLut       *lut,
                    GimpHistogram *hist,
                    gint           n_channels)
{
  gint            i, k, j;
  hist_lut_struct hlut;
  gdouble         pixels_per_value;
  gdouble         desired;
  gdouble         sum, dif;

  g_return_if_fail (lut != NULL);
  g_return_if_fail (hist != NULL);

  /* Find partition points */
  pixels_per_value = gimp_histogram_get_count (hist,
                                               GIMP_HISTOGRAM_VALUE,
                                               0, 255) / 256.0;

  for (k = 0; k < n_channels; k++)
    {
      /* First and last points in partition */
      hlut.part[k][0]   = 0;
      hlut.part[k][256] = 256;

      /* Find intermediate points */
      j   = 0;
      sum = (gimp_histogram_get_channel (hist, k, 0) +
             gimp_histogram_get_channel (hist, k, 1));

      for (i = 1; i < 256; i++)
        {
          desired = i * pixels_per_value;

          while (sum < desired && j < 256)
            {
              j++;
              sum += gimp_histogram_get_channel (hist, k, j + 1);
            }

          /* Nearest sum */
          dif = sum - gimp_histogram_get_channel (hist, k, j);

          if ((sum - desired) > (dif / 2.0))
            hlut.part[k][i] = j;
          else
            hlut.part[k][i] = j + 1;
        }
    }

  gimp_lut_setup (lut, (GimpLutFunc) equalize_lut_func, &hlut, n_channels);
}

GimpLut *
equalize_lut_new (GimpHistogram *histogram,
                  gint           n_channels)
{
  GimpLut *lut;

  g_return_val_if_fail (histogram != NULL, NULL);

  lut = gimp_lut_new ();

  equalize_lut_setup (lut, histogram, n_channels);

  return lut;
}