gimp/app/tools/gimplevelstool.c

/* The GIMP -- an 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include <gtk/gtk.h>

#include "libgimpcolor/gimpcolor.h"
#include "libgimpwidgets/gimpwidgets.h"

#include "tools-types.h"

#include "base/gimphistogram.h"
#include "base/gimplut.h"
#include "base/levels.h"

#include "core/gimp.h"
#include "core/gimpdrawable.h"
#include "core/gimpdrawable-histogram.h"
#include "core/gimpimage.h"
#include "core/gimpimagemap.h"
#include "core/gimptoolinfo.h"

#include "widgets/gimpcolorbar.h"
#include "widgets/gimphelp-ids.h"
#include "widgets/gimphistogramview.h"

#include "display/gimpdisplay.h"

#include "gimphistogramoptions.h"
#include "gimplevelstool.h"
#include "gimptoolcontrol.h"

#include "gimp-intl.h"


#define LOW_INPUT        (1 << 0)
#define GAMMA            (1 << 1)
#define HIGH_INPUT       (1 << 2)
#define LOW_OUTPUT       (1 << 3)
#define HIGH_OUTPUT      (1 << 4)
#define INPUT_LEVELS     (1 << 5)
#define OUTPUT_LEVELS    (1 << 6)
#define INPUT_SLIDERS    (1 << 7)
#define OUTPUT_SLIDERS   (1 << 8)
#define ALL_CHANNELS     (1 << 9)
#define ALL              0xFFF

#define HISTOGRAM_WIDTH   256
#define GRADIENT_HEIGHT   12
#define CONTROL_HEIGHT    8

#define LEVELS_EVENT_MASK  (GDK_BUTTON_PRESS_MASK   | \
                            GDK_BUTTON_RELEASE_MASK | \
                            GDK_BUTTON_MOTION_MASK)


/*  local function prototypes  */

static void     gimp_levels_tool_class_init  (GimpLevelsToolClass *klass);
static void     gimp_levels_tool_init        (GimpLevelsTool      *tool);
static void     gimp_levels_tool_finalize    (GObject             *object);

static gboolean gimp_levels_tool_initialize     (GimpTool         *tool,
                                                 GimpDisplay      *gdisp);

static void     gimp_levels_tool_color_picked   (GimpColorTool    *color_tool,
                                                 GimpColorPickState pick_state,
                                                 GimpImageType     sample_type,
                                                 GimpRGB          *color,
                                                 gint              color_index);

static void     gimp_levels_tool_map            (GimpImageMapTool *image_map_tool);
static void     gimp_levels_tool_dialog         (GimpImageMapTool *image_map_tool);
static void     gimp_levels_tool_reset          (GimpImageMapTool *image_map_tool);
static gboolean gimp_levels_tool_settings_load  (GimpImageMapTool *image_mao_tool,
                                                 gpointer          fp);
static gboolean gimp_levels_tool_settings_save  (GimpImageMapTool *image_map_tool,
                                                 gpointer          fp);

static void     levels_update                        (GimpLevelsTool *tool,
                                                      guint           update);
static void     levels_channel_callback              (GtkWidget      *widget,
                                                      GimpLevelsTool *tool);
static void     levels_channel_reset_callback        (GtkWidget      *widget,
                                                      GimpLevelsTool *tool);

static gboolean levels_menu_sensitivity              (gint            value,
                                                      gpointer        data);

static void     levels_stretch_callback              (GtkWidget      *widget,
                                                      GimpLevelsTool *tool);
static void     levels_low_input_adjustment_update   (GtkAdjustment  *adjustment,
                                                      GimpLevelsTool *tool);
static void     levels_gamma_adjustment_update       (GtkAdjustment  *adjustment,
                                                      GimpLevelsTool *tool);
static void     levels_high_input_adjustment_update  (GtkAdjustment  *adjustment,
                                                      GimpLevelsTool *tool);
static void     levels_low_output_adjustment_update  (GtkAdjustment  *adjustment,
                                                      GimpLevelsTool *tool);
static void     levels_high_output_adjustment_update (GtkAdjustment  *adjustment,
                                                      GimpLevelsTool *tool);
static void     levels_input_picker_toggled          (GtkWidget      *widget,
                                                      GimpLevelsTool *tool);

static gint     levels_input_area_event              (GtkWidget      *widget,
                                                      GdkEvent       *event,
                                                      GimpLevelsTool *tool);
static gboolean levels_input_area_expose             (GtkWidget      *widget,
                                                      GdkEventExpose *event,
                                                      GimpLevelsTool *tool);

static gint     levels_output_area_event             (GtkWidget      *widget,
                                                      GdkEvent       *event,
                                                      GimpLevelsTool *tool);
static gboolean levels_output_area_expose            (GtkWidget      *widget,
                                                      GdkEventExpose *event,
                                                      GimpLevelsTool *tool);


static GimpImageMapToolClass *parent_class = NULL;


/*  public functions  */

void
gimp_levels_tool_register (GimpToolRegisterCallback  callback,
                           gpointer                  data)
{
  (* callback) (GIMP_TYPE_LEVELS_TOOL,
                GIMP_TYPE_HISTOGRAM_OPTIONS,
                gimp_color_options_gui,
                0,
                "gimp-levels-tool",
                _("Levels"),
                _("Adjust color levels"),
                N_("_Levels..."), NULL,
                NULL, GIMP_HELP_TOOL_LEVELS,
                GIMP_STOCK_TOOL_LEVELS,
                data);
}

GType
gimp_levels_tool_get_type (void)
{
  static GType tool_type = 0;

  if (! tool_type)
    {
      static const GTypeInfo tool_info =
      {
        sizeof (GimpLevelsToolClass),
        (GBaseInitFunc) NULL,
        (GBaseFinalizeFunc) NULL,
        (GClassInitFunc) gimp_levels_tool_class_init,
        NULL,           /* class_finalize */
        NULL,           /* class_data     */
        sizeof (GimpLevelsTool),
        0,              /* n_preallocs    */
        (GInstanceInitFunc) gimp_levels_tool_init,
      };

      tool_type = g_type_register_static (GIMP_TYPE_IMAGE_MAP_TOOL,
                                          "GimpLevelsTool",
                                          &tool_info, 0);
    }

  return tool_type;
}


/*  private functions  */

static void
gimp_levels_tool_class_init (GimpLevelsToolClass *klass)
{
  GObjectClass          *object_class;
  GimpToolClass         *tool_class;
  GimpColorToolClass    *color_tool_class;
  GimpImageMapToolClass *image_map_tool_class;

  object_class         = G_OBJECT_CLASS (klass);
  tool_class           = GIMP_TOOL_CLASS (klass);
  color_tool_class     = GIMP_COLOR_TOOL_CLASS (klass);
  image_map_tool_class = GIMP_IMAGE_MAP_TOOL_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  object_class->finalize   = gimp_levels_tool_finalize;

  tool_class->initialize   = gimp_levels_tool_initialize;

  color_tool_class->picked = gimp_levels_tool_color_picked;

  image_map_tool_class->shell_desc        = _("Adjust Color Levels");
  image_map_tool_class->settings_name     = "levels";
  image_map_tool_class->load_dialog_title = _("Load Levels");
  image_map_tool_class->load_button_tip   = _("Load levels settings from file");
  image_map_tool_class->save_dialog_title = _("Save Levels");
  image_map_tool_class->save_button_tip   = _("Save levels settings to file");

  image_map_tool_class->map               = gimp_levels_tool_map;
  image_map_tool_class->dialog            = gimp_levels_tool_dialog;
  image_map_tool_class->reset             = gimp_levels_tool_reset;

  image_map_tool_class->settings_load     = gimp_levels_tool_settings_load;
  image_map_tool_class->settings_save     = gimp_levels_tool_settings_save;
}

static void
gimp_levels_tool_init (GimpLevelsTool *tool)
{
  tool->lut           = gimp_lut_new ();
  tool->levels        = g_new0 (Levels, 1);
  tool->hist          = NULL;
  tool->channel       = GIMP_HISTOGRAM_VALUE;
  tool->active_picker = NULL;

  levels_init (tool->levels);
}

static void
gimp_levels_tool_finalize (GObject *object)
{
  GimpLevelsTool *tool = GIMP_LEVELS_TOOL (object);

  if (tool->lut)
    {
      gimp_lut_free (tool->lut);
      tool->lut = NULL;
    }
  if (tool->levels)
    {
      g_free (tool->levels);
      tool->levels = NULL;
    }
  if (tool->hist)
    {
      gimp_histogram_free (tool->hist);
      tool->hist = NULL;
    }

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static gboolean
gimp_levels_tool_initialize (GimpTool    *tool,
                             GimpDisplay *gdisp)
{
  GimpLevelsTool *l_tool = GIMP_LEVELS_TOOL (tool);
  GimpDrawable   *drawable;

  drawable = gimp_image_active_drawable (gdisp->gimage);

  if (! drawable)
    return FALSE;

  if (gimp_drawable_is_indexed (drawable))
    {
      g_message (_("Levels for indexed layers cannot be adjusted."));
      return FALSE;
    }

  if (! l_tool->hist)
    l_tool->hist = gimp_histogram_new ();

  levels_init (l_tool->levels);

  l_tool->channel = GIMP_HISTOGRAM_VALUE;
  l_tool->color   = gimp_drawable_is_rgb (drawable);
  l_tool->alpha   = gimp_drawable_has_alpha (drawable);

  if (l_tool->active_picker)
    gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (l_tool->active_picker),
                                  FALSE);

  GIMP_TOOL_CLASS (parent_class)->initialize (tool, gdisp);

  gimp_int_combo_box_set_sensitivity (GIMP_INT_COMBO_BOX (l_tool->channel_menu),
                                      levels_menu_sensitivity, l_tool, NULL);

  gimp_int_combo_box_set_active (GIMP_INT_COMBO_BOX (l_tool->channel_menu),
                                 l_tool->channel);

  /* FIXME: hack */
  if (! l_tool->color)
    l_tool->channel = (l_tool->channel == GIMP_HISTOGRAM_ALPHA) ? 1 : 0;

  levels_update (l_tool, ALL);

  gimp_drawable_calculate_histogram (drawable, l_tool->hist);
  gimp_histogram_view_set_histogram (GIMP_HISTOGRAM_VIEW (l_tool->hist_view),
                                     l_tool->hist);

  return TRUE;
}

static void
gimp_levels_tool_map (GimpImageMapTool *image_map_tool)
{
  GimpLevelsTool *tool = GIMP_LEVELS_TOOL (image_map_tool);

  gimp_image_map_apply (image_map_tool->image_map,
                        (GimpImageMapApplyFunc) gimp_lut_process,
                        tool->lut);
}


/*******************/
/*  Levels dialog  */
/*******************/


static GtkWidget *
gimp_levels_tool_color_picker_new (GimpLevelsTool *tool,
                                   guint           value)
{
  GtkWidget   *button;
  const gchar *stock_id;
  const gchar *help;

  switch (value & 0xF)
    {
    case LOW_INPUT:
      stock_id = GIMP_STOCK_COLOR_PICKER_BLACK;
      help     = _("Pick black point");
      break;
    case GAMMA:
      stock_id = GIMP_STOCK_COLOR_PICKER_GRAY;
      help     = _("Pick gray point");
      break;
    case HIGH_INPUT:
      stock_id = GIMP_STOCK_COLOR_PICKER_WHITE;
      help     = _("Pick white point");
      break;
    default:
      return NULL;
    }

  button = g_object_new (GTK_TYPE_TOGGLE_BUTTON,
                         "label",          stock_id,
                         "use_stock",      TRUE,
                         "draw_indicator", FALSE,
                         NULL);

  gimp_help_set_help_data (button, help, NULL);

  g_object_set_data (G_OBJECT (button),
                     "pick_value", GUINT_TO_POINTER (value));
  g_signal_connect (button, "toggled",
                    G_CALLBACK (levels_input_picker_toggled),
                    tool);

  return button;
}

static void
gimp_levels_tool_dialog (GimpImageMapTool *image_map_tool)
{
  GimpLevelsTool  *tool = GIMP_LEVELS_TOOL (image_map_tool);
  GimpToolOptions *tool_options;
  GtkListStore    *store;
  GtkWidget       *vbox;
  GtkWidget       *vbox2;
  GtkWidget       *vbox3;
  GtkWidget       *hbox;
  GtkWidget       *hbox2;
  GtkWidget       *label;
  GtkWidget       *menu;
  GtkWidget       *frame;
  GtkWidget       *hbbox;
  GtkWidget       *button;
  GtkWidget       *spinbutton;
  GtkWidget       *bar;
  GtkObject       *data;
  gint             border;

  tool_options = GIMP_TOOL (tool)->tool_info->tool_options;

  vbox = image_map_tool->main_vbox;

  /*  The option menu for selecting channels  */
  hbox = gtk_hbox_new (FALSE, 6);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, FALSE, 0);
  gtk_widget_show (hbox);

  label = gtk_label_new_with_mnemonic (_("Cha_nnel:"));
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, FALSE, 0);
  gtk_widget_show (label);

  store = gimp_enum_store_new_with_range (GIMP_TYPE_HISTOGRAM_CHANNEL,
                                          GIMP_HISTOGRAM_VALUE,
                                          GIMP_HISTOGRAM_ALPHA);
  menu = g_object_new (GIMP_TYPE_ENUM_COMBO_BOX,
                       "model", store,
                       NULL);
  g_object_unref (store);

  g_signal_connect (menu, "changed",
                    G_CALLBACK (levels_channel_callback),
                    tool);
  gimp_enum_combo_box_set_stock_prefix (GIMP_ENUM_COMBO_BOX (menu),
                                        "gimp-channel");
  gtk_box_pack_start (GTK_BOX (hbox), menu, FALSE, FALSE, 0);
  gtk_widget_show (menu);

  tool->channel_menu = menu;

  gtk_label_set_mnemonic_widget (GTK_LABEL (label), menu);

  button = gtk_button_new_with_mnemonic (_("R_eset channel"));
  gtk_box_pack_start (GTK_BOX (hbox), button, FALSE, FALSE, 0);
  gtk_widget_show (button);

  g_signal_connect (button, "clicked",
                    G_CALLBACK (levels_channel_reset_callback),
                    tool);

  menu = gimp_prop_enum_stock_box_new (G_OBJECT (tool_options),
                                       "histogram-scale", "gimp-histogram",
                                       0, 0);
  gtk_box_pack_end (GTK_BOX (hbox), menu, FALSE, FALSE, 0);
  gtk_widget_show (menu);

  /*  Input levels frame  */
  frame = gimp_frame_new (_("Input Levels"));
  gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
  gtk_widget_show (frame);

  vbox2 = gtk_vbox_new (FALSE, 2);
  gtk_container_add (GTK_CONTAINER (frame), vbox2);
  gtk_widget_show (vbox2);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_box_pack_start (GTK_BOX (vbox2), frame, TRUE, TRUE, 0);
  gtk_widget_show (frame);

  tool->hist_view = gimp_histogram_view_new (FALSE);
  gtk_container_add (GTK_CONTAINER (frame), tool->hist_view);
  gtk_widget_show (GTK_WIDGET (tool->hist_view));

  gimp_histogram_options_connect_view (GIMP_HISTOGRAM_OPTIONS (tool_options),
                                       GIMP_HISTOGRAM_VIEW (tool->hist_view));

  g_object_get (tool->hist_view, "border-width", &border, NULL);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_box_pack_start (GTK_BOX (vbox2), frame, FALSE, FALSE, 0);
  gtk_widget_show (frame);

  tool->input_area = gtk_event_box_new ();
  gtk_widget_set_size_request (tool->input_area, -1,
                               GRADIENT_HEIGHT + CONTROL_HEIGHT);
  gtk_widget_add_events (tool->input_area, LEVELS_EVENT_MASK);
  gtk_container_add (GTK_CONTAINER (frame), tool->input_area);
  gtk_widget_show (tool->input_area);

  g_signal_connect (tool->input_area, "event",
                    G_CALLBACK (levels_input_area_event),
                    tool);
  g_signal_connect_after (tool->input_area, "expose_event",
                          G_CALLBACK (levels_input_area_expose),
                          tool);

  vbox3 = gtk_vbox_new (FALSE, 0);
  gtk_container_add (GTK_CONTAINER (tool->input_area), vbox3);
  gtk_widget_show (vbox3);

  tool->input_bar = g_object_new (GIMP_TYPE_COLOR_BAR,
                                  "xpad", border,
                                  "ypad", 0,
                                  NULL);
  gtk_widget_set_size_request (tool->input_bar, -1, GRADIENT_HEIGHT / 2);
  gtk_box_pack_start (GTK_BOX (vbox3), tool->input_bar, FALSE, FALSE, 0);
  gtk_widget_show (tool->input_bar);

  bar = g_object_new (GIMP_TYPE_COLOR_BAR,
                      "xpad", border,
                      "ypad", 0,
                      NULL);
  gtk_widget_set_size_request (bar, -1, GRADIENT_HEIGHT / 2);
  gtk_box_pack_start (GTK_BOX (vbox3), bar, FALSE, FALSE, 0);
  gtk_widget_show (bar);

  /*  Horizontal box for input levels spinbuttons  */
  hbox = gtk_hbox_new (FALSE, 6);
  gtk_box_pack_start (GTK_BOX (vbox2), hbox, FALSE, FALSE, 0);
  gtk_widget_show (hbox);

  /*  low input spin  */
  hbox2 = gtk_hbox_new (FALSE, 2);
  gtk_box_pack_start (GTK_BOX (hbox), hbox2, FALSE, FALSE, 0);
  gtk_widget_show (hbox2);

  button = gimp_levels_tool_color_picker_new (tool, LOW_INPUT);
  gtk_box_pack_start (GTK_BOX (hbox2), button, FALSE, FALSE, 0);
  gtk_widget_show (button);

  spinbutton = gimp_spin_button_new (&data, 0, 0, 255, 1, 10, 10, 0.5, 0);
  gtk_box_pack_start (GTK_BOX (hbox2), spinbutton, FALSE, FALSE, 0);
  gtk_widget_show (spinbutton);

  tool->low_input = GTK_ADJUSTMENT (data);
  g_signal_connect (tool->low_input, "value_changed",
                    G_CALLBACK (levels_low_input_adjustment_update),
                    tool);

  /*  input gamma spin  */
  spinbutton = gimp_spin_button_new (&data, 1, 0.1, 10, 0.01, 0.1, 1, 0.5, 2);
  gtk_box_pack_start (GTK_BOX (hbox), spinbutton, TRUE, FALSE, 0);
  gimp_help_set_help_data (spinbutton, _("Gamma"), NULL);
  gtk_widget_show (spinbutton);

  tool->gamma = GTK_ADJUSTMENT (data);
  g_signal_connect (tool->gamma, "value_changed",
                    G_CALLBACK (levels_gamma_adjustment_update),
                    tool);

  /*  high input spin  */
  hbox2 = gtk_hbox_new (FALSE, 2);
  gtk_box_pack_end (GTK_BOX (hbox), hbox2, FALSE, FALSE, 0);
  gtk_widget_show (hbox2);

  button = gimp_levels_tool_color_picker_new (tool, HIGH_INPUT);
  gtk_box_pack_start (GTK_BOX (hbox2), button, FALSE, FALSE, 0);
  gtk_widget_show (button);

  spinbutton = gimp_spin_button_new (&data, 255, 0, 255, 1, 10, 10, 0.5, 0);
  gtk_box_pack_start (GTK_BOX (hbox2), spinbutton, FALSE, FALSE, 0);
  gtk_widget_show (spinbutton);

  tool->high_input = GTK_ADJUSTMENT (data);
  g_signal_connect (tool->high_input, "value_changed",
                    G_CALLBACK (levels_high_input_adjustment_update),
                    tool);

  /*  Output levels frame  */
  frame = gimp_frame_new (_("Output Levels"));
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);
  gtk_widget_show (frame);

  vbox2 = gtk_vbox_new (FALSE, 4);
  gtk_container_add (GTK_CONTAINER (frame), vbox2);
  gtk_widget_show (vbox2);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_box_pack_start (GTK_BOX (vbox2), frame, FALSE, FALSE, 0);
  gtk_widget_show (frame);

  tool->output_area = gtk_event_box_new ();
  gtk_widget_set_size_request (tool->output_area, -1,
                               GRADIENT_HEIGHT + CONTROL_HEIGHT);
  gtk_widget_add_events (bar, LEVELS_EVENT_MASK);
  gtk_container_add (GTK_CONTAINER (frame), tool->output_area);
  gtk_widget_show (tool->output_area);

  g_signal_connect (tool->output_area, "event",
                    G_CALLBACK (levels_output_area_event),
                    tool);
  g_signal_connect_after (tool->output_area, "expose_event",
                          G_CALLBACK (levels_output_area_expose),
                          tool);

  vbox3 = gtk_vbox_new (FALSE, 0);
  gtk_container_add (GTK_CONTAINER (tool->output_area), vbox3);
  gtk_widget_show (vbox3);

  tool->output_bar = g_object_new (GIMP_TYPE_COLOR_BAR,
                                   "xpad", border,
                                   "ypad", 0,
                                   NULL);
  gtk_widget_set_size_request (tool->output_bar, -1, GRADIENT_HEIGHT);
  gtk_box_pack_start (GTK_BOX (vbox3), tool->output_bar, FALSE, FALSE, 0);
  gtk_widget_show (tool->output_bar);

  /*  Horizontal box for levels spin widgets  */
  hbox = gtk_hbox_new (FALSE, 6);
  gtk_box_pack_start (GTK_BOX (vbox2), hbox, FALSE, FALSE, 0);
  gtk_widget_show (hbox);

  /*  low output spin  */
  spinbutton = gimp_spin_button_new (&data, 0, 0, 255, 1, 10, 10, 0.5, 0);
  gtk_box_pack_start (GTK_BOX (hbox), spinbutton, FALSE, FALSE, 0);
  gtk_widget_show (spinbutton);

  tool->low_output = GTK_ADJUSTMENT (data);
  g_signal_connect (tool->low_output, "value_changed",
                    G_CALLBACK (levels_low_output_adjustment_update),
                    tool);

  /*  high output spin  */
  spinbutton = gimp_spin_button_new (&data, 255, 0, 255, 1, 10, 10, 0.5, 0);
  gtk_box_pack_end (GTK_BOX (hbox), spinbutton, FALSE, FALSE, 0);
  gtk_widget_show (spinbutton);

  tool->high_output = GTK_ADJUSTMENT (data);
  g_signal_connect (tool->high_output, "value_changed",
                    G_CALLBACK (levels_high_output_adjustment_update),
                    tool);


  frame = gimp_frame_new (_("All Channels"));
  gtk_box_pack_end (GTK_BOX (vbox), frame, FALSE, FALSE, 0);
  gtk_widget_show (frame);

  hbox = gtk_hbox_new (FALSE, 0);
  gtk_container_add (GTK_CONTAINER (frame), hbox);
  gtk_widget_show (hbox);

  hbbox = gtk_hbutton_box_new ();
  gtk_box_set_spacing (GTK_BOX (hbbox), 4);
  gtk_box_pack_start (GTK_BOX (hbox), hbbox, FALSE, FALSE, 0);
  gtk_widget_show (hbbox);

  gtk_box_pack_start (GTK_BOX (hbbox), image_map_tool->load_button,
                      FALSE, FALSE, 0);
  gtk_widget_show (image_map_tool->load_button);

  gtk_box_pack_start (GTK_BOX (hbbox), image_map_tool->save_button,
                      FALSE, FALSE, 0);
  gtk_widget_show (image_map_tool->save_button);

  hbbox = gtk_hbox_new (FALSE, 6);
  gtk_box_pack_end (GTK_BOX (hbox), hbbox, FALSE, FALSE, 0);
  gtk_widget_show (hbbox);

  button = gtk_button_new_with_mnemonic (_("_Auto"));
  gtk_box_pack_start (GTK_BOX (hbbox), button, FALSE, FALSE, 0);
  gimp_help_set_help_data (button, _("Adjust levels automatically"), NULL);
  gtk_widget_show (button);

  g_signal_connect (button, "clicked",
                    G_CALLBACK (levels_stretch_callback),
                    tool);

  button = gimp_levels_tool_color_picker_new (tool,
                                              LOW_INPUT | ALL_CHANNELS);
  gtk_box_pack_start (GTK_BOX (hbbox), button, FALSE, FALSE, 0);
  gtk_widget_show (button);

  button = gimp_levels_tool_color_picker_new (tool, GAMMA | ALL_CHANNELS);
  gtk_box_pack_start (GTK_BOX (hbbox), button, FALSE, FALSE, 0);
  gtk_widget_show (button);

  button = gimp_levels_tool_color_picker_new (tool,
                                              HIGH_INPUT | ALL_CHANNELS);
  gtk_box_pack_start (GTK_BOX (hbbox), button, FALSE, FALSE, 0);
  gtk_widget_show (button);
}

static void
gimp_levels_tool_reset (GimpImageMapTool *image_map_tool)
{
  GimpLevelsTool *tool = GIMP_LEVELS_TOOL (image_map_tool);

  levels_init (tool->levels);
  levels_update (tool, ALL);
}

static gboolean
gimp_levels_tool_settings_load (GimpImageMapTool *image_map_tool,
                                gpointer          fp)
{
  GimpLevelsTool *tool = GIMP_LEVELS_TOOL (image_map_tool);
  FILE           *file = fp;
  gint            low_input[5];
  gint            high_input[5];
  gint            low_output[5];
  gint            high_output[5];
  gdouble         gamma[5];
  gint            i, fields;
  gchar           buf[50];
  gchar          *nptr;

  if (! fgets (buf, sizeof (buf), file))
    return FALSE;

  if (strcmp (buf, "# GIMP Levels File\n") != 0)
    return FALSE;

  for (i = 0; i < 5; i++)
    {
      fields = fscanf (file, "%d %d %d %d ",
                       &low_input[i],
                       &high_input[i],
                       &low_output[i],
                       &high_output[i]);

      if (fields != 4)
        return FALSE;

      if (! fgets (buf, 50, file))
        return FALSE;

      gamma[i] = g_ascii_strtod (buf, &nptr);

      if (buf == nptr || errno == ERANGE)
        return FALSE;
    }

  for (i = 0; i < 5; i++)
    {
      tool->levels->low_input[i]   = low_input[i];
      tool->levels->high_input[i]  = high_input[i];
      tool->levels->low_output[i]  = low_output[i];
      tool->levels->high_output[i] = high_output[i];
      tool->levels->gamma[i]       = gamma[i];
    }

  levels_update (tool, ALL);

  return TRUE;
}

static gboolean
gimp_levels_tool_settings_save (GimpImageMapTool *image_map_tool,
                                gpointer          fp)
{
  GimpLevelsTool *tool = GIMP_LEVELS_TOOL (image_map_tool);
  FILE           *file = fp;
  gint            i;

  fprintf (file, "# GIMP Levels File\n");

  for (i = 0; i < 5; i++)
    {
      gchar buf[G_ASCII_DTOSTR_BUF_SIZE];

      fprintf (file, "%d %d %d %d %s\n",
               tool->levels->low_input[i],
               tool->levels->high_input[i],
               tool->levels->low_output[i],
               tool->levels->high_output[i],
               g_ascii_formatd (buf, G_ASCII_DTOSTR_BUF_SIZE, "%f",
                                tool->levels->gamma[i]));
    }

  return TRUE;
}

static void
levels_draw_slider (GtkWidget *widget,
                    GdkGC     *border_gc,
                    GdkGC     *fill_gc,
                    gint       xpos)
{
  gint y;

  for (y = 0; y < CONTROL_HEIGHT; y++)
    gdk_draw_line (widget->window, fill_gc,
                   xpos - y / 2, GRADIENT_HEIGHT + y,
                   xpos + y / 2, GRADIENT_HEIGHT + y);

  gdk_draw_line (widget->window, border_gc,
                 xpos,
                 GRADIENT_HEIGHT,
                 xpos - (CONTROL_HEIGHT - 1) / 2,
                 GRADIENT_HEIGHT + CONTROL_HEIGHT - 1);

  gdk_draw_line (widget->window, border_gc,
                 xpos,
                 GRADIENT_HEIGHT,
                 xpos + (CONTROL_HEIGHT - 1) / 2,
                 GRADIENT_HEIGHT + CONTROL_HEIGHT - 1);

  gdk_draw_line (widget->window, border_gc,
                 xpos - (CONTROL_HEIGHT - 1) / 2,
                 GRADIENT_HEIGHT + CONTROL_HEIGHT - 1,
                 xpos + (CONTROL_HEIGHT - 1) / 2,
                 GRADIENT_HEIGHT + CONTROL_HEIGHT - 1);
}

static void
levels_update (GimpLevelsTool *tool,
               guint           update)
{
  GimpHistogramChannel channel;

  if (tool->color)
    {
      channel = tool->channel;
    }
  else
    {
      /* FIXME: hack */
      if (tool->channel == 1)
        channel = GIMP_HISTOGRAM_ALPHA;
      else
        channel = GIMP_HISTOGRAM_VALUE;
    }

  /*  Recalculate the transfer arrays  */
  levels_calculate_transfers (tool->levels);

  /* set up the lut */
  if (GIMP_IMAGE_MAP_TOOL (tool)->drawable)
    gimp_lut_setup (tool->lut,
                    (GimpLutFunc) levels_lut_func,
                    tool->levels,
                    gimp_drawable_bytes (GIMP_IMAGE_MAP_TOOL (tool)->drawable));

  if (update & LOW_INPUT)
    gtk_adjustment_set_value (tool->low_input,
                              tool->levels->low_input[tool->channel]);

  if (update & GAMMA)
    gtk_adjustment_set_value (tool->gamma,
                              tool->levels->gamma[tool->channel]);

  if (update & HIGH_INPUT)
    gtk_adjustment_set_value (tool->high_input,
                              tool->levels->high_input[tool->channel]);

  if (update & LOW_OUTPUT)
    gtk_adjustment_set_value (tool->low_output,
                              tool->levels->low_output[tool->channel]);

  if (update & HIGH_OUTPUT)
    gtk_adjustment_set_value (tool->high_output,
                              tool->levels->high_output[tool->channel]);

  if (update & INPUT_LEVELS)
    {
      switch (channel)
        {
        case GIMP_HISTOGRAM_VALUE:
        case GIMP_HISTOGRAM_ALPHA:
        case GIMP_HISTOGRAM_RGB:
          gimp_color_bar_set_buffers (GIMP_COLOR_BAR (tool->input_bar),
                                      tool->levels->input[tool->channel],
                                      tool->levels->input[tool->channel],
                                      tool->levels->input[tool->channel]);
          break;

        case GIMP_HISTOGRAM_RED:
        case GIMP_HISTOGRAM_GREEN:
        case GIMP_HISTOGRAM_BLUE:
          gimp_color_bar_set_buffers (GIMP_COLOR_BAR (tool->input_bar),
                                      tool->levels->input[GIMP_HISTOGRAM_RED],
                                      tool->levels->input[GIMP_HISTOGRAM_GREEN],
                                      tool->levels->input[GIMP_HISTOGRAM_BLUE]);
          break;
        }
    }

  if (update & OUTPUT_LEVELS)
    {
      gimp_color_bar_set_channel (GIMP_COLOR_BAR (tool->output_bar), channel);
    }

  if (update & INPUT_SLIDERS)
    {
      gtk_widget_queue_draw (tool->input_area);
    }

  if (update & OUTPUT_SLIDERS)
    {
      gtk_widget_queue_draw (tool->output_area);
    }
}

static void
levels_channel_callback (GtkWidget      *widget,
                         GimpLevelsTool *tool)
{
  gimp_int_combo_box_get_active (GIMP_INT_COMBO_BOX (widget),
                                 (gint *) &tool->channel);

  gimp_histogram_view_set_channel (GIMP_HISTOGRAM_VIEW (tool->hist_view),
                                   tool->channel);

  /* FIXME: hack */
  if (! tool->color)
    tool->channel = (tool->channel == GIMP_HISTOGRAM_ALPHA) ? 1 : 0;

  levels_update (tool, ALL);
}

static void
levels_channel_reset_callback (GtkWidget      *widget,
                               GimpLevelsTool *tool)
{
  levels_channel_reset (tool->levels, tool->channel);
  levels_update (tool, ALL);

  gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
}

static gboolean
levels_menu_sensitivity (gint      value,
                         gpointer  data)
{
  GimpLevelsTool       *tool    = GIMP_LEVELS_TOOL (data);
  GimpHistogramChannel  channel = value;

  switch (channel)
    {
    case GIMP_HISTOGRAM_VALUE:
      return TRUE;

    case GIMP_HISTOGRAM_RED:
    case GIMP_HISTOGRAM_GREEN:
    case GIMP_HISTOGRAM_BLUE:
      return tool->color;

    case GIMP_HISTOGRAM_ALPHA:
      return tool->alpha;

    case GIMP_HISTOGRAM_RGB:
      return FALSE;
    }

  return FALSE;
}

static void
levels_stretch_callback (GtkWidget      *widget,
                      GimpLevelsTool *tool)
{
  levels_stretch (tool->levels, tool->hist, tool->color);
  levels_update (tool, ALL);

  gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
}

static void
levels_low_input_adjustment_update (GtkAdjustment  *adjustment,
                                    GimpLevelsTool *tool)
{
  gint value = ROUND (adjustment->value);

  value = CLAMP (value, 0, tool->levels->high_input[tool->channel]);

  /*  enforce a consistent displayed value (low_input <= high_input)  */
  gtk_adjustment_set_value (adjustment, value);

  if (tool->levels->low_input[tool->channel] != value)
    {
      tool->levels->low_input[tool->channel] = value;
      levels_update (tool, INPUT_LEVELS | INPUT_SLIDERS);

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
    }
}

static void
levels_gamma_adjustment_update (GtkAdjustment  *adjustment,
                                GimpLevelsTool *tool)
{
  if (tool->levels->gamma[tool->channel] != adjustment->value)
    {
      tool->levels->gamma[tool->channel] = adjustment->value;
      levels_update (tool, INPUT_LEVELS | INPUT_SLIDERS);

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
    }
}

static void
levels_high_input_adjustment_update (GtkAdjustment  *adjustment,
                                     GimpLevelsTool *tool)
{
  gint value = ROUND (adjustment->value);

  value = CLAMP (value, tool->levels->low_input[tool->channel], 255);

  /*  enforce a consistent displayed value (high_input >= low_input)  */
  gtk_adjustment_set_value (adjustment, value);

  if (tool->levels->high_input[tool->channel] != value)
    {
      tool->levels->high_input[tool->channel] = value;
      levels_update (tool, INPUT_LEVELS | INPUT_SLIDERS);

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
    }
}

static void
levels_low_output_adjustment_update (GtkAdjustment  *adjustment,
                                     GimpLevelsTool *tool)
{
  gint value = ROUND (adjustment->value);

  if (tool->levels->low_output[tool->channel] != value)
    {
      tool->levels->low_output[tool->channel] = value;
      levels_update (tool, OUTPUT_LEVELS | OUTPUT_SLIDERS);

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
    }
}

static void
levels_high_output_adjustment_update (GtkAdjustment  *adjustment,
                                      GimpLevelsTool *tool)
{
  gint value = ROUND (adjustment->value);

  if (tool->levels->high_output[tool->channel] != value)
    {
      tool->levels->high_output[tool->channel] = value;
      levels_update (tool, OUTPUT_LEVELS | OUTPUT_SLIDERS);

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
    }
}

static void
levels_input_picker_toggled (GtkWidget      *widget,
                             GimpLevelsTool *tool)
{
  if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (widget)))
    {
      if (tool->active_picker == widget)
        return;

      if (tool->active_picker)
        gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (tool->active_picker),
                                      FALSE);

      tool->active_picker = widget;

      gimp_color_tool_enable (GIMP_COLOR_TOOL (tool),
                              GIMP_COLOR_OPTIONS (GIMP_TOOL (tool)->tool_info->tool_options));
    }
  else if (tool->active_picker == widget)
    {
      tool->active_picker = NULL;
      gimp_color_tool_disable (GIMP_COLOR_TOOL (tool));
    }
}

static gboolean
levels_input_area_event (GtkWidget      *widget,
                         GdkEvent       *event,
                         GimpLevelsTool *tool)
{
  GdkEventButton *bevent;
  GdkEventMotion *mevent;
  gchar           text[12];
  gint            x, distance;
  gint            i;
  gboolean        update = FALSE;

  switch (event->type)
    {
    case GDK_BUTTON_PRESS:
      bevent = (GdkEventButton *) event;

      distance = G_MAXINT;
      for (i = 0; i < 3; i++)
        if (fabs (bevent->x - tool->slider_pos[i]) < distance)
          {
            tool->active_slider = i;
            distance = fabs (bevent->x - tool->slider_pos[i]);
          }

      x = bevent->x;
      update = TRUE;
      break;

    case GDK_BUTTON_RELEASE:
      switch (tool->active_slider)
        {
        case 0:  /*  low input  */
          levels_update (tool, LOW_INPUT | GAMMA);
          break;
        case 1:  /*  gamma  */
          levels_update (tool, GAMMA);
          break;
        case 2:  /*  high input  */
          levels_update (tool, HIGH_INPUT | GAMMA);
          break;
        }

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
      break;

    case GDK_MOTION_NOTIFY:
      mevent = (GdkEventMotion *) event;
      gdk_window_get_pointer (widget->window, &x, NULL, NULL);
      update = TRUE;
      break;

    default:
      break;
    }

  if (update)
    {
      gdouble  delta, mid, tmp;
      gint     width;
      gint     border;

      g_object_get (tool->hist_view, "border-width", &border, NULL);

      width = widget->allocation.width - 2 * border;

      if (width < 1)
        return FALSE;

      switch (tool->active_slider)
        {
        case 0:  /*  low input  */
          tool->levels->low_input[tool->channel] =
            ((gdouble) (x - border) / (gdouble) width) * 255.0;

          tool->levels->low_input[tool->channel] =
            CLAMP (tool->levels->low_input[tool->channel],
                   0, tool->levels->high_input[tool->channel]);
          break;

        case 1:  /*  gamma  */
          delta = (gdouble) (tool->slider_pos[2] - tool->slider_pos[0]) / 2.0;
          mid   = tool->slider_pos[0] + delta;

          x   = CLAMP (x, tool->slider_pos[0], tool->slider_pos[2]);
          tmp = (gdouble) (x - mid) / delta;

          tool->levels->gamma[tool->channel] = 1.0 / pow (10, tmp);

          /*  round the gamma value to the nearest 1/100th  */
          sprintf (text, "%2.2f", tool->levels->gamma[tool->channel]);
          tool->levels->gamma[tool->channel] = atof (text);
          break;

        case 2:  /*  high input  */
          tool->levels->high_input[tool->channel] =
            ((gdouble) (x - border) / (gdouble) width) * 255.0;

          tool->levels->high_input[tool->channel] =
            CLAMP (tool->levels->high_input[tool->channel],
                   tool->levels->low_input[tool->channel], 255);
          break;
        }

      levels_update (tool, INPUT_SLIDERS | INPUT_LEVELS);
    }

  return FALSE;
}


static gboolean
levels_input_area_expose (GtkWidget      *widget,
                          GdkEventExpose *event,
                          GimpLevelsTool *tool)
{
  Levels  *levels = tool->levels;
  gint     width  = widget->allocation.width;
  gdouble  delta, mid, tmp;
  gint     border;

  g_object_get (tool->hist_view, "border-width", &border, NULL);

  width -= 2 * border;

  tool->slider_pos[0] = ROUND ((gdouble) width *
                               levels->low_input[tool->channel] /
                               256.0) + border;

  tool->slider_pos[2] = ROUND ((gdouble) width *
                               levels->high_input[tool->channel] /
                               256.0) + border;

  delta = (gdouble) (tool->slider_pos[2] - tool->slider_pos[0]) / 2.0;
  mid   = tool->slider_pos[0] + delta;
  tmp   = log10 (1.0 / levels->gamma[tool->channel]);

  tool->slider_pos[1] = ROUND (mid + delta * tmp) + border;

  levels_draw_slider (widget,
                      widget->style->black_gc,
                      widget->style->black_gc,
                      tool->slider_pos[0]);
  levels_draw_slider (widget,
                      widget->style->black_gc,
                      widget->style->dark_gc[GTK_STATE_NORMAL],
                      tool->slider_pos[1]);
  levels_draw_slider (widget,
                      widget->style->black_gc,
                      widget->style->white_gc,
                      tool->slider_pos[2]);

  return FALSE;
}

static gboolean
levels_output_area_event (GtkWidget      *widget,
                          GdkEvent       *event,
                          GimpLevelsTool *tool)
{
  GdkEventButton *bevent;
  GdkEventMotion *mevent;
  gint            x, distance;
  gint            i;
  gboolean        update = FALSE;

  switch (event->type)
    {
    case GDK_BUTTON_PRESS:
      bevent = (GdkEventButton *) event;

      distance = G_MAXINT;
      for (i = 3; i < 5; i++)
        if (fabs (bevent->x - tool->slider_pos[i]) < distance)
          {
            tool->active_slider = i;
            distance = fabs (bevent->x - tool->slider_pos[i]);
          }

      x = bevent->x;
      update = TRUE;
      break;

    case GDK_BUTTON_RELEASE:
      switch (tool->active_slider)
        {
        case 3:  /*  low output  */
          levels_update (tool, LOW_OUTPUT);
          break;
        case 4:  /*  high output  */
          levels_update (tool, HIGH_OUTPUT);
          break;
        }

      gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
      break;

    case GDK_MOTION_NOTIFY:
      mevent = (GdkEventMotion *) event;
      gdk_window_get_pointer (widget->window, &x, NULL, NULL);
      update = TRUE;
      break;

    default:
      break;
    }

  if (update)
    {
      gint  width;
      gint  border;

      g_object_get (tool->hist_view, "border-width", &border, NULL);

      width = widget->allocation.width - 2 * border;

      if (width < 1)
        return FALSE;

      switch (tool->active_slider)
        {
        case 3:  /*  low output  */
          tool->levels->low_output[tool->channel] =
            ((gdouble) (x - border) / (gdouble) width) * 255.0;

          tool->levels->low_output[tool->channel] =
            CLAMP (tool->levels->low_output[tool->channel], 0, 255);
          break;

        case 4:  /*  high output  */
          tool->levels->high_output[tool->channel] =
            ((gdouble) (x - border) / (gdouble) width) * 255.0;

          tool->levels->high_output[tool->channel] =
            CLAMP (tool->levels->high_output[tool->channel], 0, 255);
          break;
        }

      levels_update (tool, OUTPUT_SLIDERS);
    }

  return FALSE;
}

static gboolean
levels_output_area_expose (GtkWidget      *widget,
                           GdkEventExpose *event,
                           GimpLevelsTool *tool)
{
  Levels  *levels = tool->levels;
  gint     width  = widget->allocation.width;
  gint     border;

  g_object_get (tool->hist_view, "border-width", &border, NULL);

  width -= 2 * border;

  tool->slider_pos[3] = ROUND ((gdouble) width *
                               levels->low_output[tool->channel] /
                               256.0) + border;

  tool->slider_pos[4] = ROUND ((gdouble) width *
                               levels->high_output[tool->channel] /
                               256.0) + border;

  levels_draw_slider (widget,
                      widget->style->black_gc,
                      widget->style->black_gc,
                      tool->slider_pos[3]);
  levels_draw_slider (widget,
                      widget->style->black_gc,
                      widget->style->white_gc,
                      tool->slider_pos[4]);

  return FALSE;
}

static void
levels_input_adjust_by_color (Levels               *levels,
                              guint                 value,
                              GimpHistogramChannel  channel,
                              guchar               *color)
{
  switch (value & 0xF)
    {
    case LOW_INPUT:
      levels_adjust_by_colors (levels, channel, color, NULL, NULL);
      break;
    case GAMMA:
      levels_adjust_by_colors (levels, channel, NULL, color, NULL);
      break;
    case HIGH_INPUT:
      levels_adjust_by_colors (levels, channel, NULL, NULL, color);
      break;
    default:
      break;
    }
}

static void
gimp_levels_tool_color_picked (GimpColorTool      *color_tool,
                               GimpColorPickState  pick_state,
                               GimpImageType       sample_type,
                               GimpRGB            *color,
                               gint                color_index)
{
  GimpLevelsTool *tool = GIMP_LEVELS_TOOL (color_tool);
  guchar          col[5];
  guint           value;

  gimp_rgba_get_uchar (color,
                       col + RED_PIX,
                       col + GREEN_PIX,
                       col + BLUE_PIX,
                       col + ALPHA_PIX);

  value = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (tool->active_picker),
                                               "pick_value"));

  if (value & ALL_CHANNELS && GIMP_IMAGE_TYPE_IS_RGB (sample_type))
    {
      GimpHistogramChannel  channel;

      /*  first reset the value channel  */
      switch (value & 0xF)
        {
        case LOW_INPUT:
          tool->levels->low_input[GIMP_HISTOGRAM_VALUE] = 0;
          break;
        case GAMMA:
          tool->levels->gamma[GIMP_HISTOGRAM_VALUE] = 1.0;
          break;
        case HIGH_INPUT:
          tool->levels->high_input[GIMP_HISTOGRAM_VALUE] = 255;
          break;
        default:
          break;
        }

      /*  then adjust all color channels  */
      for (channel = GIMP_HISTOGRAM_RED;
           channel <= GIMP_HISTOGRAM_BLUE;
           channel++)
        {
          levels_input_adjust_by_color (tool->levels,
                                        value, channel, col);
        }
    }
  else
    {
      levels_input_adjust_by_color (tool->levels,
                                    value, tool->channel, col);
    }

  levels_update (tool, ALL);

  gimp_image_map_tool_preview (GIMP_IMAGE_MAP_TOOL (tool));
}