Adding upstream version 2.10.36.upstream/2.10.36

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 964 insertions, 0 deletions

diff --git a/app/operations/gimplevelsconfig.c b/app/operations/gimplevelsconfig.c
new file mode 100644
index 0000000..df5d349
--- /dev/null
+++ b/app/operations/gimplevelsconfig.c
@@ -0,0 +1,964 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimplevelsconfig.c
+ * Copyright (C) 2007 Michael Natterer <mitch@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 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 <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <errno.h>
+
+#include <cairo.h>
+#include <gegl.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "libgimpbase/gimpbase.h"
+#include "libgimpcolor/gimpcolor.h"
+#include "libgimpmath/gimpmath.h"
+#include "libgimpconfig/gimpconfig.h"
+
+#include "operations-types.h"
+
+#include "core/gimp-utils.h"
+#include "core/gimpcurve.h"
+#include "core/gimphistogram.h"
+
+#include "gimpcurvesconfig.h"
+#include "gimplevelsconfig.h"
+#include "gimpoperationlevels.h"
+
+#include "gimp-intl.h"
+
+
+enum
+{
+  PROP_0,
+  PROP_LINEAR,
+  PROP_CHANNEL,
+  PROP_LOW_INPUT,
+  PROP_HIGH_INPUT,
+  PROP_CLAMP_INPUT,
+  PROP_GAMMA,
+  PROP_LOW_OUTPUT,
+  PROP_HIGH_OUTPUT,
+  PROP_CLAMP_OUTPUT
+};
+
+
+static void     gimp_levels_config_iface_init   (GimpConfigInterface *iface);
+
+static void     gimp_levels_config_get_property (GObject          *object,
+                                                 guint             property_id,
+                                                 GValue           *value,
+                                                 GParamSpec       *pspec);
+static void     gimp_levels_config_set_property (GObject          *object,
+                                                 guint             property_id,
+                                                 const GValue     *value,
+                                                 GParamSpec       *pspec);
+
+static gboolean gimp_levels_config_serialize    (GimpConfig       *config,
+                                                 GimpConfigWriter *writer,
+                                                 gpointer          data);
+static gboolean gimp_levels_config_deserialize  (GimpConfig       *config,
+                                                 GScanner         *scanner,
+                                                 gint              nest_level,
+                                                 gpointer          data);
+static gboolean gimp_levels_config_equal        (GimpConfig       *a,
+                                                 GimpConfig       *b);
+static void     gimp_levels_config_reset        (GimpConfig       *config);
+static gboolean gimp_levels_config_copy         (GimpConfig       *src,
+                                                 GimpConfig       *dest,
+                                                 GParamFlags       flags);
+
+
+G_DEFINE_TYPE_WITH_CODE (GimpLevelsConfig, gimp_levels_config,
+                         GIMP_TYPE_OPERATION_SETTINGS,
+                         G_IMPLEMENT_INTERFACE (GIMP_TYPE_CONFIG,
+                                                gimp_levels_config_iface_init))
+
+#define parent_class gimp_levels_config_parent_class
+
+
+static void
+gimp_levels_config_class_init (GimpLevelsConfigClass *klass)
+{
+  GObjectClass      *object_class   = G_OBJECT_CLASS (klass);
+  GimpViewableClass *viewable_class = GIMP_VIEWABLE_CLASS (klass);
+
+  object_class->set_property        = gimp_levels_config_set_property;
+  object_class->get_property        = gimp_levels_config_get_property;
+
+  viewable_class->default_icon_name = "gimp-tool-levels";
+
+  GIMP_CONFIG_PROP_BOOLEAN (object_class, PROP_LINEAR,
+                            "linear",
+                            _("Linear"),
+                            _("Work on linear RGB"),
+                            FALSE, 0);
+
+  GIMP_CONFIG_PROP_ENUM (object_class, PROP_CHANNEL,
+                         "channel",
+                         _("Channel"),
+                         _("The affected channel"),
+                         GIMP_TYPE_HISTOGRAM_CHANNEL,
+                         GIMP_HISTOGRAM_VALUE, 0);
+
+  GIMP_CONFIG_PROP_DOUBLE (object_class, PROP_LOW_INPUT,
+                           "low-input",
+                           _("Low Input"),
+                           _("Low Input"),
+                           0.0, 1.0, 0.0, 0);
+
+  GIMP_CONFIG_PROP_DOUBLE (object_class, PROP_HIGH_INPUT,
+                           "high-input",
+                           _("High Input"),
+                           _("High Input"),
+                           0.0, 1.0, 1.0, 0);
+
+  GIMP_CONFIG_PROP_BOOLEAN (object_class, PROP_CLAMP_INPUT,
+                           "clamp-input",
+                           _("Clamp Input"),
+                           _("Clamp input values before applying output mapping."),
+                            FALSE, 0);
+
+  GIMP_CONFIG_PROP_DOUBLE (object_class, PROP_GAMMA,
+                           "gamma",
+                           _("Gamma"),
+                           _("Gamma"),
+                           0.1, 10.0, 1.0, 0);
+
+  GIMP_CONFIG_PROP_DOUBLE (object_class, PROP_LOW_OUTPUT,
+                           "low-output",
+                           _("Low Output"),
+                           _("Low Output"),
+                           0.0, 1.0, 0.0, 0);
+
+  GIMP_CONFIG_PROP_DOUBLE (object_class, PROP_HIGH_OUTPUT,
+                           "high-output",
+                           _("High Output"),
+                           _("High Output"),
+                           0.0, 1.0, 1.0, 0);
+
+  GIMP_CONFIG_PROP_BOOLEAN (object_class, PROP_CLAMP_OUTPUT,
+                           "clamp-output",
+                           _("Clamp Output"),
+                           _("Clamp final output values."),
+                            FALSE, 0);
+}
+
+static void
+gimp_levels_config_iface_init (GimpConfigInterface *iface)
+{
+  iface->serialize   = gimp_levels_config_serialize;
+  iface->deserialize = gimp_levels_config_deserialize;
+  iface->equal       = gimp_levels_config_equal;
+  iface->reset       = gimp_levels_config_reset;
+  iface->copy        = gimp_levels_config_copy;
+}
+
+static void
+gimp_levels_config_init (GimpLevelsConfig *self)
+{
+  gimp_config_reset (GIMP_CONFIG (self));
+}
+
+static void
+gimp_levels_config_get_property (GObject    *object,
+                                 guint       property_id,
+                                 GValue     *value,
+                                 GParamSpec *pspec)
+{
+  GimpLevelsConfig *self = GIMP_LEVELS_CONFIG (object);
+
+  switch (property_id)
+    {
+    case PROP_LINEAR:
+      g_value_set_boolean (value, self->linear);
+      break;
+
+    case PROP_CHANNEL:
+      g_value_set_enum (value, self->channel);
+      break;
+
+    case PROP_LOW_INPUT:
+      g_value_set_double (value, self->low_input[self->channel]);
+      break;
+
+    case PROP_HIGH_INPUT:
+      g_value_set_double (value, self->high_input[self->channel]);
+      break;
+
+    case PROP_CLAMP_INPUT:
+      g_value_set_boolean (value, self->clamp_input);
+      break;
+
+    case PROP_GAMMA:
+      g_value_set_double (value, self->gamma[self->channel]);
+      break;
+
+    case PROP_LOW_OUTPUT:
+      g_value_set_double (value, self->low_output[self->channel]);
+      break;
+
+    case PROP_HIGH_OUTPUT:
+      g_value_set_double (value, self->high_output[self->channel]);
+      break;
+
+    case PROP_CLAMP_OUTPUT:
+      g_value_set_boolean (value, self->clamp_output);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static void
+gimp_levels_config_set_property (GObject      *object,
+                                 guint         property_id,
+                                 const GValue *value,
+                                 GParamSpec   *pspec)
+{
+  GimpLevelsConfig *self = GIMP_LEVELS_CONFIG (object);
+
+  switch (property_id)
+    {
+    case PROP_LINEAR:
+      self->linear = g_value_get_boolean (value);
+      break;
+
+    case PROP_CHANNEL:
+      self->channel = g_value_get_enum (value);
+      g_object_notify (object, "low-input");
+      g_object_notify (object, "high-input");
+      g_object_notify (object, "gamma");
+      g_object_notify (object, "low-output");
+      g_object_notify (object, "high-output");
+      break;
+
+    case PROP_LOW_INPUT:
+      self->low_input[self->channel] = g_value_get_double (value);
+      break;
+
+    case PROP_HIGH_INPUT:
+      self->high_input[self->channel] = g_value_get_double (value);
+      break;
+
+    case PROP_CLAMP_INPUT:
+      self->clamp_input = g_value_get_boolean (value);
+      break;
+
+    case PROP_GAMMA:
+      self->gamma[self->channel] = g_value_get_double (value);
+      break;
+
+    case PROP_LOW_OUTPUT:
+      self->low_output[self->channel] = g_value_get_double (value);
+      break;
+
+    case PROP_HIGH_OUTPUT:
+      self->high_output[self->channel] = g_value_get_double (value);
+      break;
+
+    case PROP_CLAMP_OUTPUT:
+      self->clamp_output = g_value_get_boolean (value);
+      break;
+
+   default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static gboolean
+gimp_levels_config_serialize (GimpConfig       *config,
+                              GimpConfigWriter *writer,
+                              gpointer          data)
+{
+  GimpLevelsConfig     *l_config = GIMP_LEVELS_CONFIG (config);
+  GimpHistogramChannel  channel;
+  GimpHistogramChannel  old_channel;
+  gboolean              success = TRUE;
+
+  if (! gimp_operation_settings_config_serialize_base (config, writer, data)    ||
+      ! gimp_config_serialize_property_by_name (config, "linear",       writer) ||
+      ! gimp_config_serialize_property_by_name (config, "clamp-input",  writer) ||
+      ! gimp_config_serialize_property_by_name (config, "clamp-output", writer))
+    return FALSE;
+
+  old_channel = l_config->channel;
+
+  for (channel = GIMP_HISTOGRAM_VALUE;
+       channel <= GIMP_HISTOGRAM_ALPHA;
+       channel++)
+    {
+      l_config->channel = channel;
+
+      /*  serialize the channel properties manually (not using
+       *  gimp_config_serialize_properties()), so the parent class'
+       *  properties don't end up in the config file one per channel.
+       *  See bug #700653.
+       */
+      success =
+        (gimp_config_serialize_property_by_name (config, "channel",     writer) &&
+         gimp_config_serialize_property_by_name (config, "low-input",   writer) &&
+         gimp_config_serialize_property_by_name (config, "high-input",  writer) &&
+         gimp_config_serialize_property_by_name (config, "gamma",       writer) &&
+         gimp_config_serialize_property_by_name (config, "low-output",  writer) &&
+         gimp_config_serialize_property_by_name (config, "high-output", writer));
+
+      if (! success)
+        break;
+    }
+
+  l_config->channel = old_channel;
+
+  return success;
+}
+
+static gboolean
+gimp_levels_config_deserialize (GimpConfig *config,
+                                GScanner   *scanner,
+                                gint        nest_level,
+                                gpointer    data)
+{
+  GimpLevelsConfig     *l_config = GIMP_LEVELS_CONFIG (config);
+  GimpHistogramChannel  old_channel;
+  gboolean              success = TRUE;
+
+  old_channel = l_config->channel;
+
+  success = gimp_config_deserialize_properties (config, scanner, nest_level);
+
+  g_object_set (config, "channel", old_channel, NULL);
+
+  return success;
+}
+
+static gboolean
+gimp_levels_config_equal (GimpConfig *a,
+                          GimpConfig *b)
+{
+  GimpLevelsConfig     *config_a = GIMP_LEVELS_CONFIG (a);
+  GimpLevelsConfig     *config_b = GIMP_LEVELS_CONFIG (b);
+  GimpHistogramChannel  channel;
+
+  if (! gimp_operation_settings_config_equal_base (a, b) ||
+      config_a->linear       != config_b->linear         ||
+      config_a->clamp_input  != config_b->clamp_input    ||
+      config_a->clamp_output != config_b->clamp_output)
+    return FALSE;
+
+  for (channel = GIMP_HISTOGRAM_VALUE;
+       channel <= GIMP_HISTOGRAM_ALPHA;
+       channel++)
+    {
+      if (config_a->gamma[channel]       != config_b->gamma[channel]      ||
+          config_a->low_input[channel]   != config_b->low_input[channel]  ||
+          config_a->high_input[channel]  != config_b->high_input[channel] ||
+          config_a->low_output[channel]  != config_b->low_output[channel] ||
+          config_a->high_output[channel] != config_b->high_output[channel])
+        return FALSE;
+    }
+
+  /* don't compare "channel" */
+
+  return TRUE;
+}
+
+static void
+gimp_levels_config_reset (GimpConfig *config)
+{
+  GimpLevelsConfig     *l_config = GIMP_LEVELS_CONFIG (config);
+  GimpHistogramChannel  channel;
+
+  gimp_operation_settings_config_reset_base (config);
+
+  for (channel = GIMP_HISTOGRAM_VALUE;
+       channel <= GIMP_HISTOGRAM_ALPHA;
+       channel++)
+    {
+      l_config->channel = channel;
+      gimp_levels_config_reset_channel (l_config);
+    }
+
+  gimp_config_reset_property (G_OBJECT (config), "linear");
+  gimp_config_reset_property (G_OBJECT (config), "channel");
+  gimp_config_reset_property (G_OBJECT (config), "clamp-input");
+  gimp_config_reset_property (G_OBJECT (config), "clamp_output");
+}
+
+static gboolean
+gimp_levels_config_copy (GimpConfig  *src,
+                         GimpConfig  *dest,
+                         GParamFlags  flags)
+{
+  GimpLevelsConfig     *src_config  = GIMP_LEVELS_CONFIG (src);
+  GimpLevelsConfig     *dest_config = GIMP_LEVELS_CONFIG (dest);
+  GimpHistogramChannel  channel;
+
+  if (! gimp_operation_settings_config_copy_base (src, dest, flags))
+    return FALSE;
+
+  for (channel = GIMP_HISTOGRAM_VALUE;
+       channel <= GIMP_HISTOGRAM_ALPHA;
+       channel++)
+    {
+      dest_config->gamma[channel]       = src_config->gamma[channel];
+      dest_config->low_input[channel]   = src_config->low_input[channel];
+      dest_config->high_input[channel]  = src_config->high_input[channel];
+      dest_config->low_output[channel]  = src_config->low_output[channel];
+      dest_config->high_output[channel] = src_config->high_output[channel];
+    }
+
+  g_object_notify (G_OBJECT (dest), "gamma");
+  g_object_notify (G_OBJECT (dest), "low-input");
+  g_object_notify (G_OBJECT (dest), "high-input");
+  g_object_notify (G_OBJECT (dest), "low-output");
+  g_object_notify (G_OBJECT (dest), "high-output");
+
+  dest_config->linear       = src_config->linear;
+  dest_config->channel      = src_config->channel;
+  dest_config->clamp_input  = src_config->clamp_input;
+  dest_config->clamp_output = src_config->clamp_output;
+
+  g_object_notify (G_OBJECT (dest), "linear");
+  g_object_notify (G_OBJECT (dest), "channel");
+  g_object_notify (G_OBJECT (dest), "clamp-input");
+  g_object_notify (G_OBJECT (dest), "clamp-output");
+
+  return TRUE;
+}
+
+
+/*  public functions  */
+
+void
+gimp_levels_config_reset_channel (GimpLevelsConfig *config)
+{
+  g_return_if_fail (GIMP_IS_LEVELS_CONFIG (config));
+
+  g_object_freeze_notify (G_OBJECT (config));
+
+  gimp_config_reset_property (G_OBJECT (config), "gamma");
+  gimp_config_reset_property (G_OBJECT (config), "low-input");
+  gimp_config_reset_property (G_OBJECT (config), "high-input");
+  gimp_config_reset_property (G_OBJECT (config), "low-output");
+  gimp_config_reset_property (G_OBJECT (config), "high-output");
+
+  g_object_thaw_notify (G_OBJECT (config));
+}
+
+void
+gimp_levels_config_stretch (GimpLevelsConfig *config,
+                            GimpHistogram    *histogram,
+                            gboolean          is_color)
+{
+  g_return_if_fail (GIMP_IS_LEVELS_CONFIG (config));
+  g_return_if_fail (histogram != NULL);
+
+  g_object_freeze_notify (G_OBJECT (config));
+
+  if (is_color)
+    {
+      GimpHistogramChannel channel;
+
+      /*  Set the overall value to defaults  */
+      channel = config->channel;
+      config->channel = GIMP_HISTOGRAM_VALUE;
+      gimp_levels_config_reset_channel (config);
+      config->channel = channel;
+
+      for (channel = GIMP_HISTOGRAM_RED;
+           channel <= GIMP_HISTOGRAM_BLUE;
+           channel++)
+        {
+          gimp_levels_config_stretch_channel (config, histogram, channel);
+        }
+    }
+  else
+    {
+      gimp_levels_config_stretch_channel (config, histogram,
+                                          GIMP_HISTOGRAM_VALUE);
+    }
+
+  g_object_thaw_notify (G_OBJECT (config));
+}
+
+void
+gimp_levels_config_stretch_channel (GimpLevelsConfig     *config,
+                                    GimpHistogram        *histogram,
+                                    GimpHistogramChannel  channel)
+{
+  gdouble count;
+  gdouble bias = 0.006;
+  gint    n_bins;
+  gint    i;
+
+  g_return_if_fail (GIMP_IS_LEVELS_CONFIG (config));
+  g_return_if_fail (histogram != NULL);
+
+  g_object_freeze_notify (G_OBJECT (config));
+
+  config->gamma[channel]       = 1.0;
+  config->low_output[channel]  = 0.0;
+  config->high_output[channel] = 1.0;
+
+  n_bins = gimp_histogram_n_bins (histogram);
+  count  = gimp_histogram_get_count (histogram, channel, 0, n_bins - 1);
+
+  if (count == 0.0)
+    {
+      config->low_input[channel]  = 0.0;
+      config->high_input[channel] = 0.0;
+    }
+  else
+    {
+      gdouble new_count;
+      gdouble percentage;
+      gdouble next_percentage;
+
+      /*  Set the low input  */
+      new_count = 0.0;
+
+      for (i = 0; i < (n_bins - 1); i++)
+        {
+          new_count += gimp_histogram_get_value (histogram, channel, i);
+          percentage = new_count / count;
+          next_percentage = (new_count +
+                             gimp_histogram_get_value (histogram,
+                                                       channel,
+                                                       i + 1)) / count;
+
+          if (fabs (percentage - bias) < fabs (next_percentage - bias))
+            {
+              config->low_input[channel] = (gdouble) (i + 1) / (n_bins - 1);
+              break;
+            }
+        }
+
+      /*  Set the high input  */
+      new_count = 0.0;
+
+      for (i = (n_bins - 1); i > 0; i--)
+        {
+          new_count += gimp_histogram_get_value (histogram, channel, i);
+          percentage = new_count / count;
+          next_percentage = (new_count +
+                             gimp_histogram_get_value (histogram,
+                                                       channel,
+                                                       i - 1)) / count;
+
+          if (fabs (percentage - bias) < fabs (next_percentage - bias))
+            {
+              config->high_input[channel] = (gdouble) (i - 1) / (n_bins - 1);
+              break;
+            }
+        }
+    }
+
+  g_object_notify (G_OBJECT (config), "gamma");
+  g_object_notify (G_OBJECT (config), "low-input");
+  g_object_notify (G_OBJECT (config), "high-input");
+  g_object_notify (G_OBJECT (config), "low-output");
+  g_object_notify (G_OBJECT (config), "high-output");
+
+  g_object_thaw_notify (G_OBJECT (config));
+}
+
+static gdouble
+gimp_levels_config_input_from_color (GimpHistogramChannel  channel,
+                                     const GimpRGB        *color)
+{
+  switch (channel)
+    {
+    case GIMP_HISTOGRAM_VALUE:
+      return MAX (MAX (color->r, color->g), color->b);
+
+    case GIMP_HISTOGRAM_RED:
+      return color->r;
+
+    case GIMP_HISTOGRAM_GREEN:
+      return color->g;
+
+    case GIMP_HISTOGRAM_BLUE:
+      return color->b;
+
+    case GIMP_HISTOGRAM_ALPHA:
+      return color->a;
+
+    case GIMP_HISTOGRAM_RGB:
+      return MIN (MIN (color->r, color->g), color->b);
+
+    case GIMP_HISTOGRAM_LUMINANCE:
+      return GIMP_RGB_LUMINANCE (color->r, color->g, color->b);
+    }
+
+  return 0.0;
+}
+
+void
+gimp_levels_config_adjust_by_colors (GimpLevelsConfig     *config,
+                                     GimpHistogramChannel  channel,
+                                     const GimpRGB        *black,
+                                     const GimpRGB        *gray,
+                                     const GimpRGB        *white)
+{
+  g_return_if_fail (GIMP_IS_LEVELS_CONFIG (config));
+
+  g_object_freeze_notify (G_OBJECT (config));
+
+  if (black)
+    {
+      config->low_input[channel] = gimp_levels_config_input_from_color (channel,
+                                                                        black);
+      g_object_notify (G_OBJECT (config), "low-input");
+    }
+
+
+  if (white)
+    {
+      config->high_input[channel] = gimp_levels_config_input_from_color (channel,
+                                                                         white);
+      g_object_notify (G_OBJECT (config), "high-input");
+    }
+
+  if (gray)
+    {
+      gdouble input;
+      gdouble range;
+      gdouble inten;
+      gdouble out_light;
+      gdouble lightness;
+
+      /* Calculate lightness value */
+      lightness = GIMP_RGB_LUMINANCE (gray->r, gray->g, gray->b);
+
+      input = gimp_levels_config_input_from_color (channel, gray);
+
+      range = config->high_input[channel] - config->low_input[channel];
+      if (range <= 0)
+        goto out;
+
+      input -= config->low_input[channel];
+      if (input < 0)
+        goto out;
+
+      /* Normalize input and lightness */
+      inten = input / range;
+      out_light = lightness / range;
+
+      /* See bug 622054: picking pure black or white as gamma doesn't
+       * work. But we cannot compare to 0.0 or 1.0 because cpus and
+       * compilers are shit. If you try to check out_light using
+       * printf() it will give exact 0.0 or 1.0 anyway, probably
+       * because the generated code is different and out_light doesn't
+       * live in a register. That must be why the cpu/compiler mafia
+       * invented epsilon and defined this shit to be the programmer's
+       * responsibility.
+       */
+      if (out_light <= 0.0001 || out_light >= 0.9999)
+        goto out;
+
+      /* Map selected color to corresponding lightness */
+      config->gamma[channel] = log (inten) / log (out_light);
+      config->gamma[channel] = CLAMP (config->gamma[channel], 0.1, 10.0);
+      g_object_notify (G_OBJECT (config), "gamma");
+    }
+
+ out:
+  g_object_thaw_notify (G_OBJECT (config));
+}
+
+GimpCurvesConfig *
+gimp_levels_config_to_curves_config (GimpLevelsConfig *config)
+{
+  GimpCurvesConfig     *curves;
+  GimpHistogramChannel  channel;
+
+  g_return_val_if_fail (GIMP_IS_LEVELS_CONFIG (config), NULL);
+
+  curves = g_object_new (GIMP_TYPE_CURVES_CONFIG, NULL);
+
+  gimp_operation_settings_config_copy_base (GIMP_CONFIG (config),
+                                            GIMP_CONFIG (curves),
+                                            0);
+
+  curves->linear = config->linear;
+
+  for (channel = GIMP_HISTOGRAM_VALUE;
+       channel <= GIMP_HISTOGRAM_ALPHA;
+       channel++)
+    {
+      GimpCurve  *curve    = curves->curve[channel];
+      static const gint n  = 8;
+      gdouble     gamma    = config->gamma[channel];
+      gdouble     delta_in;
+      gdouble     delta_out;
+      gdouble     x, y;
+
+      /* clear the points set by default */
+      gimp_curve_clear_points (curve);
+
+      delta_in  = config->high_input[channel] - config->low_input[channel];
+      delta_out = config->high_output[channel] - config->low_output[channel];
+
+      x = config->low_input[channel];
+      y = config->low_output[channel];
+
+      gimp_curve_add_point (curve, x, y);
+
+      if (delta_out != 0 && gamma != 1.0)
+        {
+          /* The Levels tool performs gamma adjustment, which is a
+           * power law, while the Curves tool uses cubic Bézier
+           * curves. Here we try to approximate this gamma adjustment
+           * with a Bézier curve with 5 control points. Two of them
+           * must be (low_input, low_output) and (high_input,
+           * high_output), so we need to add 3 more control points in
+           * the middle.
+           */
+          gint i;
+
+          if (gamma > 1)
+            {
+              /* Case no. 1: γ > 1
+               *
+               * The curve should look like a horizontal
+               * parabola. Since its curvature is greatest when x is
+               * small, we add more control points there, so the
+               * approximation is more accurate. I decided to set the
+               * length of the consecutive segments to x₀, γ⋅x₀, γ²⋅x₀
+               * and γ³⋅x₀ and I saw that the curves looked
+               * good. Still, this is completely arbitrary.
+               */
+              gdouble dx = 0;
+              gdouble x0;
+
+              for (i = 0; i < n; ++i)
+                dx = dx * gamma + 1;
+              x0 = delta_in / dx;
+
+              dx = 0;
+              for (i = 1; i < n; ++i)
+                {
+                  dx = dx * gamma + x0;
+                  x = config->low_input[channel] + dx;
+                  y = config->low_output[channel] + delta_out *
+                      gimp_operation_levels_map_input (config, channel, x);
+                  gimp_curve_add_point (curve, x, y);
+                }
+            }
+          else
+            {
+              /* Case no. 2: γ < 1
+               *
+               * The curve is the same as the one in case no. 1,
+               * observed through a reflexion along the y = x axis. So
+               * if we invert γ and swap the x and y axes we can use
+               * the same method as in case no. 1.
+               */
+              GimpLevelsConfig *config_inv;
+              gdouble           dy = 0;
+              gdouble           y0;
+              const gdouble     gamma_inv = 1 / gamma;
+
+              config_inv = gimp_config_duplicate (GIMP_CONFIG (config));
+
+              config_inv->gamma[channel]       = gamma_inv;
+              config_inv->low_input[channel]   = config->low_output[channel];
+              config_inv->low_output[channel]  = config->low_input[channel];
+              config_inv->high_input[channel]  = config->high_output[channel];
+              config_inv->high_output[channel] = config->high_input[channel];
+
+              for (i = 0; i < n; ++i)
+                dy = dy * gamma_inv + 1;
+              y0 = delta_out / dy;
+
+              dy = 0;
+              for (i = 1; i < n; ++i)
+                {
+                  dy = dy * gamma_inv + y0;
+                  y = config->low_output[channel] + dy;
+                  x = config->low_input[channel] + delta_in *
+                      gimp_operation_levels_map_input (config_inv, channel, y);
+                  gimp_curve_add_point (curve, x, y);
+                }
+
+              g_object_unref (config_inv);
+            }
+        }
+
+      x = config->high_input[channel];
+      y = config->high_output[channel];
+
+      gimp_curve_add_point (curve, x, y);
+    }
+
+  return curves;
+}
+
+gboolean
+gimp_levels_config_load_cruft (GimpLevelsConfig  *config,
+                               GInputStream      *input,
+                               GError           **error)
+{
+  GDataInputStream *data_input;
+  gint              low_input[5];
+  gint              high_input[5];
+  gint              low_output[5];
+  gint              high_output[5];
+  gdouble           gamma[5];
+  gchar            *line;
+  gsize             line_len;
+  gint              i;
+
+  g_return_val_if_fail (GIMP_IS_LEVELS_CONFIG (config), FALSE);
+  g_return_val_if_fail (G_IS_INPUT_STREAM (input), FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  data_input = g_data_input_stream_new (input);
+
+  line_len = 64;
+  line = gimp_data_input_stream_read_line_always (data_input, &line_len,
+                                                  NULL, error);
+  if (! line)
+    return FALSE;
+
+  if (strcmp (line, "# GIMP Levels File") != 0)
+    {
+      g_set_error_literal (error, GIMP_CONFIG_ERROR, GIMP_CONFIG_ERROR_PARSE,
+                           _("not a GIMP Levels file"));
+      g_object_unref (data_input);
+      g_free (line);
+      return FALSE;
+    }
+
+  g_free (line);
+
+  for (i = 0; i < 5; i++)
+    {
+      gchar  float_buf[32];
+      gchar *endp;
+      gint   fields;
+
+      line_len = 64;
+      line = gimp_data_input_stream_read_line_always (data_input, &line_len,
+                                                      NULL, error);
+      if (! line)
+        {
+          g_object_unref (data_input);
+          return FALSE;
+        }
+
+      fields = sscanf (line, "%d %d %d %d %31s",
+                       &low_input[i],
+                       &high_input[i],
+                       &low_output[i],
+                       &high_output[i],
+                       float_buf);
+
+      g_free (line);
+
+      if (fields != 5)
+        goto error;
+
+      gamma[i] = g_ascii_strtod (float_buf, &endp);
+
+      if (endp == float_buf || errno == ERANGE)
+        goto error;
+    }
+
+  g_object_unref (data_input);
+
+  g_object_freeze_notify (G_OBJECT (config));
+
+  for (i = 0; i < 5; i++)
+    {
+      config->low_input[i]   = low_input[i]   / 255.0;
+      config->high_input[i]  = high_input[i]  / 255.0;
+      config->gamma[i]       = gamma[i];
+      config->low_output[i]  = low_output[i]  / 255.0;
+      config->high_output[i] = high_output[i] / 255.0;
+    }
+
+  config->linear       = FALSE;
+  config->clamp_input  = TRUE;
+  config->clamp_output = TRUE;
+
+  g_object_notify (G_OBJECT (config), "linear");
+  g_object_notify (G_OBJECT (config), "low-input");
+  g_object_notify (G_OBJECT (config), "high-input");
+  g_object_notify (G_OBJECT (config), "clamp-input");
+  g_object_notify (G_OBJECT (config), "gamma");
+  g_object_notify (G_OBJECT (config), "low-output");
+  g_object_notify (G_OBJECT (config), "high-output");
+  g_object_notify (G_OBJECT (config), "clamp-output");
+
+  g_object_thaw_notify (G_OBJECT (config));
+
+  return TRUE;
+
+ error:
+  g_object_unref (data_input);
+
+  g_set_error_literal (error, GIMP_CONFIG_ERROR, GIMP_CONFIG_ERROR_PARSE,
+                       _("parse error"));
+  return FALSE;
+}
+
+gboolean
+gimp_levels_config_save_cruft (GimpLevelsConfig  *config,
+                               GOutputStream     *output,
+                               GError           **error)
+{
+  GString *string;
+  gint     i;
+
+  g_return_val_if_fail (GIMP_IS_LEVELS_CONFIG (config), FALSE);
+  g_return_val_if_fail (G_IS_OUTPUT_STREAM (output), FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  string = g_string_new ("# GIMP Levels File\n");
+
+  for (i = 0; i < 5; i++)
+    {
+      gchar buf[G_ASCII_DTOSTR_BUF_SIZE];
+
+      g_string_append_printf (string,
+                              "%d %d %d %d %s\n",
+                              (gint) (config->low_input[i]   * 255.999),
+                              (gint) (config->high_input[i]  * 255.999),
+                              (gint) (config->low_output[i]  * 255.999),
+                              (gint) (config->high_output[i] * 255.999),
+                              g_ascii_dtostr (buf, G_ASCII_DTOSTR_BUF_SIZE,
+                                              config->gamma[i]));
+    }
+
+  if (! g_output_stream_write_all (output, string->str, string->len,
+                                   NULL, NULL, error))
+    {
+      g_prefix_error (error, _("Writing levels file failed: "));
+      g_string_free (string, TRUE);
+      return FALSE;
+    }
+
+  g_string_free (string, TRUE);
+
+  return TRUE;
+}