/* 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 <stdlib.h>
#include <string.h>
#include <math.h>
#include "appenv.h"
#include "actionarea.h"
#include "buildmenu.h"
#include "colormaps.h"
#include "drawable.h"
#include "general.h"
#include "gdisplay.h"
#include "histogramwidget.h"
#include "gimphistogram.h"
#include "image_map.h"
#include "interface.h"
#include "levels.h"
#include "gimplut.h"
#include "lut_funcs.h"

#include "libgimp/gimpintl.h"

#define LOW_INPUT          0x1
#define GAMMA              0x2
#define HIGH_INPUT         0x4
#define LOW_OUTPUT         0x8
#define HIGH_OUTPUT        0x10
#define INPUT_LEVELS       0x20
#define OUTPUT_LEVELS      0x40
#define INPUT_SLIDERS      0x80
#define OUTPUT_SLIDERS     0x100
#define DRAW               0x200
#define ALL                0xFFF

#define TEXT_WIDTH       45
#define DA_WIDTH         256
#define DA_HEIGHT        25
#define GRADIENT_HEIGHT  15
#define CONTROL_HEIGHT   DA_HEIGHT - GRADIENT_HEIGHT
#define HISTOGRAM_WIDTH  256
#define HISTOGRAM_HEIGHT 150

#define LEVELS_DA_MASK  GDK_EXPOSURE_MASK | \
                        GDK_ENTER_NOTIFY_MASK | \
			GDK_BUTTON_PRESS_MASK | \
			GDK_BUTTON_RELEASE_MASK | \
			GDK_BUTTON1_MOTION_MASK | \
			GDK_POINTER_MOTION_HINT_MASK

/*  the levels structures  */

typedef struct _Levels Levels;
struct _Levels
{
  int x, y;    /*  coords for last mouse click  */
};

typedef struct _LevelsDialog LevelsDialog;
struct _LevelsDialog
{
  GtkWidget *    shell;
  GtkWidget *    low_input_spin;
  GtkAdjustment *low_input_adj;
  GtkWidget *    gamma_text;
  GtkWidget *    high_input_spin;
  GtkAdjustment *high_input_adj;
  GtkWidget *    low_output_spin;
  GtkAdjustment *low_output_adj;
  GtkWidget *    high_output_spin;
  GtkAdjustment *high_output_adj;
  GtkWidget *    input_levels_da[2];
  GtkWidget *    output_levels_da[2];
  GtkWidget *    channel_menu;
  HistogramWidget *histogram;
  GimpHistogram   *hist;

  GimpDrawable * drawable;
  ImageMap       image_map;
  int            color;
  int            channel;
  int            low_input[5];
  double         gamma[5];
  int            high_input[5];
  int            low_output[5];
  int            high_output[5];
  gint           preview;

  int            active_slider;
  int            slider_pos[5];  /*  positions for the five sliders  */

  unsigned char  input[5][256]; /* this is used only by the gui */

  GimpLut       *lut;
};


/*  the levels tool options  */
static ToolOptions *levels_options = NULL;

/*  the levels tool dialog  */
static LevelsDialog *levels_dialog = NULL;


/*  levels action functions  */
static void   levels_button_press   (Tool *, GdkEventButton *, gpointer);
static void   levels_button_release (Tool *, GdkEventButton *, gpointer);
static void   levels_motion         (Tool *, GdkEventMotion *, gpointer);
static void   levels_cursor_update  (Tool *, GdkEventMotion *, gpointer);
static void   levels_control        (Tool *, ToolAction,       gpointer);

static LevelsDialog * levels_new_dialog (void);

static void   levels_calculate_transfers     (LevelsDialog *);
static void   levels_update                  (LevelsDialog *, int);
static void   levels_preview                 (LevelsDialog *);
static void   levels_value_callback          (GtkWidget *, gpointer);
static void   levels_red_callback            (GtkWidget *, gpointer);
static void   levels_green_callback          (GtkWidget *, gpointer);
static void   levels_blue_callback           (GtkWidget *, gpointer);
static void   levels_alpha_callback          (GtkWidget *, gpointer);
static void   levels_auto_levels_callback    (GtkWidget *, gpointer);
static void   levels_ok_callback             (GtkWidget *, gpointer);
static void   levels_cancel_callback         (GtkWidget *, gpointer);
static gint   levels_delete_callback         (GtkWidget *, GdkEvent *, gpointer);
static void   levels_preview_update          (GtkWidget *, gpointer);
static void   levels_low_input_spin_update   (GtkWidget *, gpointer);
static void   levels_gamma_text_update       (GtkWidget *, gpointer);
static void   levels_high_input_spin_update  (GtkWidget *, gpointer);
static void   levels_low_output_spin_update  (GtkWidget *, gpointer);
static void   levels_high_output_spin_update (GtkWidget *, gpointer);
static gint   levels_input_da_events         (GtkWidget *, GdkEvent *,
					      LevelsDialog *);
static gint   levels_output_da_events        (GtkWidget *, GdkEvent *,
					      LevelsDialog *);

static void   levels_histogram_range         (HistogramWidget *,
					      int, int, void *);

static void
levels_histogram_range (HistogramWidget *h,
			int              start,
			int              end,
			void            *user_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) user_data;

  histogram_widget_range (ld->histogram, -1, -1);
}

/*  levels action functions  */

static void
levels_button_press (Tool           *tool,
		     GdkEventButton *bevent,
		     gpointer        gdisp_ptr)
{
  GDisplay *gdisp;

  gdisp = gdisp_ptr;
  tool->drawable = gimage_active_drawable (gdisp->gimage);
}

static void
levels_button_release (Tool           *tool,
		       GdkEventButton *bevent,
		       gpointer        gdisp_ptr)
{
}

static void
levels_motion (Tool           *tool,
	       GdkEventMotion *mevent,
	       gpointer        gdisp_ptr)
{
}

static void
levels_cursor_update (Tool           *tool,
		      GdkEventMotion *mevent,
		      gpointer        gdisp_ptr)
{
  GDisplay *gdisp;

  gdisp = (GDisplay *) gdisp_ptr;
  gdisplay_install_tool_cursor (gdisp, GDK_TOP_LEFT_ARROW);
}

static void
levels_control (Tool       *tool,
		ToolAction  action,
		gpointer    gdisp_ptr)
{
  switch (action)
    {
    case PAUSE:
      break;

    case RESUME:
      break;

    case HALT:
      if (levels_dialog)
	levels_cancel_callback (NULL, (gpointer) levels_dialog);
      break;

    default:
      break;
    }
}

Tool *
tools_new_levels ()
{
  Tool * tool;
  Levels * private;

  /*  The tool options  */
  if (! levels_options)
    {
      levels_options = tool_options_new (_("Levels Options"));
      tools_register (LEVELS, levels_options);
    }

  tool = (Tool *) g_malloc (sizeof (Tool));
  private = (Levels *) g_malloc (sizeof (Levels));

  tool->type = LEVELS;
  tool->state = INACTIVE;
  tool->scroll_lock = 1;  /*  Disallow scrolling  */
  tool->auto_snap_to = TRUE;
  tool->private = (void *) private;

  tool->button_press_func = levels_button_press;
  tool->button_release_func = levels_button_release;
  tool->motion_func = levels_motion;
  tool->arrow_keys_func = standard_arrow_keys_func;
  tool->modifier_key_func = standard_modifier_key_func;
  tool->cursor_update_func = levels_cursor_update;
  tool->control_func = levels_control;
  tool->preserve = FALSE;
  tool->gdisp_ptr = NULL;
  tool->drawable = NULL;

  return tool;
}

void
tools_free_levels (Tool *tool)
{
  Levels * _levels;

  _levels = (Levels *) tool->private;

  /*  Close the color select dialog  */
  if (levels_dialog)
    levels_cancel_callback (NULL, (gpointer) levels_dialog);

  g_free (_levels);
}

static MenuItem color_option_items[] =
{
  { N_("Value"), 0, 0, levels_value_callback, NULL, NULL, NULL },
  { N_("Red"), 0, 0, levels_red_callback, NULL, NULL, NULL },
  { N_("Green"), 0, 0, levels_green_callback, NULL, NULL, NULL },
  { N_("Blue"), 0, 0, levels_blue_callback, NULL, NULL, NULL },
  { N_("Alpha"), 0, 0, levels_alpha_callback, NULL, NULL, NULL },
  { NULL, 0, 0, NULL, NULL, NULL, NULL }
};

void
levels_initialize (GDisplay *gdisp)
{
  int i;

  if (drawable_indexed (gimage_active_drawable (gdisp->gimage)))
    {
      g_message (_("Levels for indexed drawables cannot be adjusted."));
      return;
    }

  /*  The levels dialog  */
  if (!levels_dialog)
    levels_dialog = levels_new_dialog ();
  else
    if (!GTK_WIDGET_VISIBLE (levels_dialog->shell))
      gtk_widget_show (levels_dialog->shell);

  /*  Initialize the values  */
  levels_dialog->channel = HISTOGRAM_VALUE;
  for (i = 0; i < 5; i++)
    {
      levels_dialog->low_input[i] = 0;
      levels_dialog->gamma[i] = 1.0;
      levels_dialog->high_input[i] = 255;
      levels_dialog->low_output[i] = 0;
      levels_dialog->high_output[i] = 255;
    }

  levels_dialog->drawable = gimage_active_drawable (gdisp->gimage);
  levels_dialog->color = drawable_color (levels_dialog->drawable);
  levels_dialog->image_map = image_map_create (gdisp, levels_dialog->drawable);

  /* check for alpha channel */
  if (drawable_has_alpha (levels_dialog->drawable))
    gtk_widget_set_sensitive( color_option_items[4].widget, TRUE);
  else 
    gtk_widget_set_sensitive( color_option_items[4].widget, FALSE);
  
  /*  hide or show the channel menu based on image type  */
  if (levels_dialog->color)
    for (i = 0; i < 4; i++) 
       gtk_widget_set_sensitive( color_option_items[i].widget, TRUE);
  else 
    for (i = 1; i < 4; i++) 
       gtk_widget_set_sensitive( color_option_items[i].widget, FALSE);

  /* set the current selection */
  gtk_option_menu_set_history ( GTK_OPTION_MENU (levels_dialog->channel_menu), 0);


  levels_update (levels_dialog, LOW_INPUT | GAMMA | HIGH_INPUT | LOW_OUTPUT | HIGH_OUTPUT | DRAW);
  levels_update (levels_dialog, INPUT_LEVELS | OUTPUT_LEVELS);

  gimp_histogram_calculate_drawable (levels_dialog->hist,
				     levels_dialog->drawable);
  histogram_widget_update(levels_dialog->histogram, levels_dialog->hist);
  histogram_widget_range (levels_dialog->histogram, -1, -1);
}

void
levels_free ()
{
  if (levels_dialog)
    {
      if (levels_dialog->image_map)
	{
	  active_tool->preserve = TRUE;
	  image_map_abort (levels_dialog->image_map);
	  active_tool->preserve = FALSE;
	  levels_dialog->image_map = NULL;
	}
      gtk_widget_destroy (levels_dialog->shell);
    }
}

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

static LevelsDialog *
levels_new_dialog ()
{
  LevelsDialog *ld;
  GtkWidget *vbox;
  GtkWidget *hbox;
  GtkWidget *vbox2;
  GtkWidget *label;
  GtkWidget *frame;
  GtkWidget *toggle;
  GtkWidget *channel_hbox;
  GtkWidget *menu;
  int i;

  static ActionAreaItem action_items[] =
  {
    { N_("Auto Levels"), levels_auto_levels_callback, NULL, NULL },
    { N_("OK"), levels_ok_callback, NULL, NULL },
    { N_("Cancel"), levels_cancel_callback, NULL, NULL }
  };

  ld = g_malloc (sizeof (LevelsDialog));
  ld->preview = TRUE;

  ld->lut  = gimp_lut_new();
  ld->hist = gimp_histogram_new();

  for (i = 0; i < 5; i++)
    color_option_items [i].user_data = (gpointer) ld;

  /*  The shell and main vbox  */
  ld->shell = gtk_dialog_new ();
  gtk_window_set_wmclass (GTK_WINDOW (ld->shell), "levels", "Gimp");
  gtk_window_set_title (GTK_WINDOW (ld->shell), _("Levels"));

  /* handle the wm close signal */
  gtk_signal_connect (GTK_OBJECT (ld->shell), "delete_event",
		      GTK_SIGNAL_FUNC (levels_delete_callback),
		      ld);

  vbox = gtk_vbox_new (FALSE, 2);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 2);
  gtk_box_pack_start (GTK_BOX (GTK_DIALOG (ld->shell)->vbox), vbox, TRUE, TRUE, 0);

  /*  The option menu for selecting channels  */
  channel_hbox = gtk_hbox_new (FALSE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), channel_hbox, FALSE, FALSE, 0);

  label = gtk_label_new (_("Modify Levels for Channel: "));
  gtk_box_pack_start (GTK_BOX (channel_hbox), label, FALSE, FALSE, 0);

  menu = build_menu (color_option_items, NULL);
  ld->channel_menu = gtk_option_menu_new ();
  gtk_box_pack_start (GTK_BOX (channel_hbox), ld->channel_menu, FALSE, FALSE, 2);

  gtk_widget_show (label);
  gtk_widget_show (ld->channel_menu);
  gtk_widget_show (channel_hbox);
  gtk_option_menu_set_menu (GTK_OPTION_MENU (ld->channel_menu), menu);

  /*  Horizontal box for levels text and spin widgets  */
  hbox = gtk_hbox_new (TRUE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, FALSE, 0);

  label = gtk_label_new (_("Input Levels: "));
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, FALSE, 0);
  gtk_widget_show (label);

  /*  low input spin  */
  ld->low_input_adj = GTK_ADJUSTMENT(gtk_adjustment_new (0, 0, 255, 1, 10, 10));
  ld->low_input_spin = gtk_spin_button_new (ld->low_input_adj, 0.5, 0);
  gtk_spin_button_set_numeric(GTK_SPIN_BUTTON(ld->low_input_spin), TRUE);
  gtk_box_pack_start (GTK_BOX (hbox), ld->low_input_spin, FALSE, FALSE, 0);

  gtk_signal_connect (GTK_OBJECT (ld->low_input_adj), "value_changed",
                      (GtkSignalFunc) levels_low_input_spin_update,
                      ld);
  gtk_widget_show (ld->low_input_spin);

  /* input gamma text  */
  ld->gamma_text = gtk_entry_new ();
  gtk_entry_set_text (GTK_ENTRY (ld->gamma_text), "1.0");
  gtk_widget_set_usize (ld->gamma_text, TEXT_WIDTH, 25);
  gtk_box_pack_start (GTK_BOX (hbox), ld->gamma_text, FALSE, FALSE, 0);
  gtk_signal_connect (GTK_OBJECT (ld->gamma_text), "changed",
		      (GtkSignalFunc) levels_gamma_text_update,
		      ld);
  gtk_widget_show (ld->gamma_text);
  gtk_widget_show (hbox);

  /* high input spin  */
  ld->high_input_adj = GTK_ADJUSTMENT(gtk_adjustment_new (255, 0, 255, 1, 10, 10));
  ld->high_input_spin = gtk_spin_button_new (ld->high_input_adj, 0.5, 0);
  gtk_spin_button_set_numeric(GTK_SPIN_BUTTON(ld->high_input_spin), TRUE);
  gtk_box_pack_start (GTK_BOX (hbox), ld->high_input_spin, FALSE, FALSE, 0);

  gtk_signal_connect (GTK_OBJECT (ld->high_input_adj), "value_changed",
		      (GtkSignalFunc) levels_high_input_spin_update,
		      ld);
  gtk_widget_show (ld->high_input_spin);
  gtk_widget_show (hbox);

  /*  The levels histogram  */
  hbox = gtk_hbox_new (TRUE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, FALSE, 0);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (hbox), frame, TRUE, FALSE, 0);
  ld->histogram = histogram_widget_new(HISTOGRAM_WIDTH, HISTOGRAM_HEIGHT);

  gtk_signal_connect (GTK_OBJECT (ld->histogram), "rangechanged",
		      (GtkSignalFunc) levels_histogram_range,
		      (void*)ld);
  gtk_container_add (GTK_CONTAINER (frame), GTK_WIDGET(ld->histogram));
  gtk_widget_show (GTK_WIDGET(ld->histogram));
  gtk_widget_show (frame);
  gtk_widget_show (hbox);

  /*  The input levels drawing area  */
  hbox = gtk_hbox_new (TRUE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, FALSE, 0);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (hbox), frame, FALSE, FALSE, 0);
  vbox2 = gtk_vbox_new (FALSE, 2);
  gtk_container_add (GTK_CONTAINER (frame), vbox2);
  ld->input_levels_da[0] = gtk_preview_new (GTK_PREVIEW_GRAYSCALE);
  gtk_preview_size (GTK_PREVIEW (ld->input_levels_da[0]), DA_WIDTH, GRADIENT_HEIGHT);
  gtk_widget_set_events (ld->input_levels_da[0], LEVELS_DA_MASK);
  gtk_signal_connect (GTK_OBJECT (ld->input_levels_da[0]), "event",
		      (GtkSignalFunc) levels_input_da_events,
		      ld);
  gtk_box_pack_start (GTK_BOX (vbox2), ld->input_levels_da[0], FALSE, TRUE, 0);
  ld->input_levels_da[1] = gtk_drawing_area_new ();
  gtk_drawing_area_size (GTK_DRAWING_AREA (ld->input_levels_da[1]), DA_WIDTH, CONTROL_HEIGHT);
  gtk_widget_set_events (ld->input_levels_da[1], LEVELS_DA_MASK);
  gtk_signal_connect (GTK_OBJECT (ld->input_levels_da[1]), "event",
		      (GtkSignalFunc) levels_input_da_events,
		      ld);
  gtk_box_pack_start (GTK_BOX (vbox2), ld->input_levels_da[1], FALSE, TRUE, 0);
  gtk_widget_show (ld->input_levels_da[0]);
  gtk_widget_show (ld->input_levels_da[1]);
  gtk_widget_show (vbox2);
  gtk_widget_show (frame);
  gtk_widget_show (hbox);

  /*  Horizontal box for levels spin widgets  */
  hbox = gtk_hbox_new (TRUE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, FALSE, 0);

  label = gtk_label_new (_("Output Levels: "));
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, FALSE, 0);
  gtk_widget_show (label);

  /*  low output spin  */
  ld->low_output_adj = GTK_ADJUSTMENT(gtk_adjustment_new (0, 0, 255, 1, 10, 10));
  ld->low_output_spin = gtk_spin_button_new (ld->low_output_adj, 0.5, 0);
  gtk_spin_button_set_numeric(GTK_SPIN_BUTTON(ld->low_input_spin), TRUE);
  gtk_box_pack_start (GTK_BOX (hbox), ld->low_output_spin, FALSE, FALSE, 0);

  gtk_signal_connect (GTK_OBJECT (ld->low_output_adj), "value_changed",
                      (GtkSignalFunc) levels_low_output_spin_update,
                      ld);
  gtk_widget_show (ld->low_output_spin);

  /*  high output spin  */
  ld->high_output_adj = GTK_ADJUSTMENT(gtk_adjustment_new (255, 0, 255, 1, 10, 10));
  ld->high_output_spin = gtk_spin_button_new (ld->high_output_adj, 0.5, 0);
  gtk_spin_button_set_numeric(GTK_SPIN_BUTTON(ld->high_input_spin), TRUE);
  gtk_box_pack_start (GTK_BOX (hbox), ld->high_output_spin, FALSE, FALSE, 0);

  gtk_signal_connect (GTK_OBJECT (ld->high_output_adj), "value_changed",
                      (GtkSignalFunc) levels_high_output_spin_update,
                      ld);
  gtk_widget_show (ld->high_output_spin);
  gtk_widget_show (hbox);

  /*  The output levels drawing area  */
  hbox = gtk_hbox_new (TRUE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, FALSE, 0);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (hbox), frame, FALSE, FALSE, 0);
  vbox2 = gtk_vbox_new (FALSE, 2);
  gtk_container_add (GTK_CONTAINER (frame), vbox2);
  ld->output_levels_da[0] = gtk_preview_new (GTK_PREVIEW_GRAYSCALE);
  gtk_preview_size (GTK_PREVIEW (ld->output_levels_da[0]), DA_WIDTH, GRADIENT_HEIGHT);
  gtk_widget_set_events (ld->output_levels_da[0], LEVELS_DA_MASK);
  gtk_signal_connect (GTK_OBJECT (ld->output_levels_da[0]), "event",
		      (GtkSignalFunc) levels_output_da_events,
		      ld);
  gtk_box_pack_start (GTK_BOX (vbox2), ld->output_levels_da[0], FALSE, TRUE, 0);
  ld->output_levels_da[1] = gtk_preview_new (GTK_PREVIEW_GRAYSCALE);
  gtk_preview_size (GTK_PREVIEW (ld->output_levels_da[1]), DA_WIDTH, CONTROL_HEIGHT);
  gtk_widget_set_events (ld->output_levels_da[1], LEVELS_DA_MASK);
  gtk_signal_connect (GTK_OBJECT (ld->output_levels_da[1]), "event",
		      (GtkSignalFunc) levels_output_da_events,
		      ld);
  gtk_box_pack_start (GTK_BOX (vbox2), ld->output_levels_da[1], FALSE, TRUE, 0);
  gtk_widget_show (ld->output_levels_da[0]);
  gtk_widget_show (ld->output_levels_da[1]);
  gtk_widget_show (vbox2);
  gtk_widget_show (frame);
  gtk_widget_show (hbox);

  /*  Horizontal box for preview  */
  hbox = gtk_hbox_new (TRUE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, FALSE, 0);

  /*  The preview toggle  */
  toggle = gtk_check_button_new_with_label (_("Preview"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (toggle), ld->preview);
  gtk_box_pack_start (GTK_BOX (hbox), toggle, TRUE, FALSE, 0);
  gtk_signal_connect (GTK_OBJECT (toggle), "toggled",
		      (GtkSignalFunc) levels_preview_update,
		      ld);

  gtk_widget_show (label);
  gtk_widget_show (toggle);
  gtk_widget_show (hbox);

  /*  The action area  */
  action_items[0].user_data = ld;
  action_items[1].user_data = ld;
  action_items[2].user_data = ld;
  build_action_area (GTK_DIALOG (ld->shell), action_items, 3, 0);

  gtk_widget_show (vbox);
  gtk_widget_show (ld->shell);

  return ld;
}

static void
levels_draw_slider (GdkWindow *window,
		    GdkGC     *border_gc,
		    GdkGC     *fill_gc,
		    int        xpos)
{
  int y;

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

  gdk_draw_line(window, border_gc, xpos, 0,
		xpos - (CONTROL_HEIGHT - 1) / 2,  CONTROL_HEIGHT - 1);

  gdk_draw_line(window, border_gc, xpos, 0,
		xpos + (CONTROL_HEIGHT - 1) / 2, CONTROL_HEIGHT - 1);

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

static void
levels_erase_slider (GdkWindow *window,
		     int        xpos)
{
  gdk_window_clear_area (window, xpos - (CONTROL_HEIGHT - 1) / 2, 0,
			 CONTROL_HEIGHT - 1, CONTROL_HEIGHT);
}

static void
levels_calculate_transfers (LevelsDialog *ld)
{
  double inten;
  int i, j;

  /*  Recalculate the levels arrays  */
  for (j = 0; j < 5; j++)
    {
      for (i = 0; i < 256; i++)
	{
	  /*  determine input intensity  */
	  if (ld->high_input[j] != ld->low_input[j])
	    inten = (double) (i - ld->low_input[j]) /
	      (double) (ld->high_input[j] - ld->low_input[j]);
	  else
	    inten = (double) (i - ld->low_input[j]);

	  inten = BOUNDS (inten, 0.0, 1.0);
	  if (ld->gamma[j] != 0.0)
	    inten = pow (inten, (1.0 / ld->gamma[j]));
	  ld->input[j][i] = (unsigned char) (inten * 255.0 + 0.5);
	}
    }
}

static void
levels_update (LevelsDialog *ld,
	       int           update)
{
  char text[12];
  int i;

  /*  Recalculate the transfer arrays  */
  levels_calculate_transfers (ld);
  /* set up the lut */
  levels_lut_setup(ld->lut, ld->gamma, ld->low_input, ld->high_input,
		   ld->low_output, ld->high_output,
		   gimp_drawable_bytes(ld->drawable));

  if (update & LOW_INPUT)
    {
      gtk_spin_button_set_value (GTK_SPIN_BUTTON(ld->low_input_spin),
                                 ld->low_input[ld->channel]);
    }
  if (update & GAMMA)
    {
      sprintf (text, "%2.2f", ld->gamma[ld->channel]);
      gtk_entry_set_text (GTK_ENTRY (ld->gamma_text), text);
    }
  if (update & HIGH_INPUT)
    {
      gtk_spin_button_set_value (GTK_SPIN_BUTTON(ld->high_input_spin),
                                 ld->high_input[ld->channel]);
    }
  if (update & LOW_OUTPUT)
    {
      gtk_spin_button_set_value (GTK_SPIN_BUTTON(ld->low_output_spin),
                                 ld->low_output[ld->channel]);
    }
  if (update & HIGH_OUTPUT)
    {
      gtk_spin_button_set_value (GTK_SPIN_BUTTON(ld->high_output_spin),
                                 ld->high_output[ld->channel]);
    }
  if (update & INPUT_LEVELS)
    {
      for (i = 0; i < GRADIENT_HEIGHT; i++)
	gtk_preview_draw_row (GTK_PREVIEW (ld->input_levels_da[0]),
			      ld->input[ld->channel], 0, i, DA_WIDTH);

      if (update & DRAW)
	gtk_widget_draw (ld->input_levels_da[0], NULL);
    }
  if (update & OUTPUT_LEVELS)
    {
      unsigned char buf[DA_WIDTH];

      for (i = 0; i < DA_WIDTH; i++)
	buf[i] = i;

      for (i = 0; i < GRADIENT_HEIGHT; i++)
	gtk_preview_draw_row (GTK_PREVIEW (ld->output_levels_da[0]),
			      buf, 0, i, DA_WIDTH);

      if (update & DRAW)
	gtk_widget_draw (ld->output_levels_da[0], NULL);
    }
  if (update & INPUT_SLIDERS)
    {
      double width, mid, tmp;

      levels_erase_slider (ld->input_levels_da[1]->window, ld->slider_pos[0]);
      levels_erase_slider (ld->input_levels_da[1]->window, ld->slider_pos[1]);
      levels_erase_slider (ld->input_levels_da[1]->window, ld->slider_pos[2]);

      ld->slider_pos[0] = DA_WIDTH * ((double) ld->low_input[ld->channel] / 255.0);
      ld->slider_pos[2] = DA_WIDTH * ((double) ld->high_input[ld->channel] / 255.0);

      width = (double) (ld->slider_pos[2] - ld->slider_pos[0]) / 2.0;
      mid = ld->slider_pos[0] + width;
      tmp = log10 (1.0 / ld->gamma[ld->channel]);
      ld->slider_pos[1] = (int) (mid + width * tmp + 0.5);

      levels_draw_slider (ld->input_levels_da[1]->window,
			  ld->input_levels_da[1]->style->black_gc,
			  ld->input_levels_da[1]->style->dark_gc[GTK_STATE_NORMAL],
			  ld->slider_pos[1]);
      levels_draw_slider (ld->input_levels_da[1]->window,
			  ld->input_levels_da[1]->style->black_gc,
			  ld->input_levels_da[1]->style->black_gc,
			  ld->slider_pos[0]);
      levels_draw_slider (ld->input_levels_da[1]->window,
			  ld->input_levels_da[1]->style->black_gc,
			  ld->input_levels_da[1]->style->white_gc,
			  ld->slider_pos[2]);
    }
  if (update & OUTPUT_SLIDERS)
    {
      levels_erase_slider (ld->output_levels_da[1]->window, ld->slider_pos[3]);
      levels_erase_slider (ld->output_levels_da[1]->window, ld->slider_pos[4]);

      ld->slider_pos[3] = DA_WIDTH * ((double) ld->low_output[ld->channel] / 255.0);
      ld->slider_pos[4] = DA_WIDTH * ((double) ld->high_output[ld->channel] / 255.0);

      levels_draw_slider (ld->output_levels_da[1]->window,
			  ld->output_levels_da[1]->style->black_gc,
			  ld->output_levels_da[1]->style->black_gc,
			  ld->slider_pos[3]);
      levels_draw_slider (ld->output_levels_da[1]->window,
			  ld->output_levels_da[1]->style->black_gc,
			  ld->output_levels_da[1]->style->white_gc,
			  ld->slider_pos[4]);
    }
}

static void
levels_preview (LevelsDialog *ld)
{
  if (!ld->image_map)
    g_warning ("No image map");
  active_tool->preserve = TRUE;
  image_map_apply (ld->image_map,  (ImageMapApplyFunc)gimp_lut_process_2,
		   (void *) ld->lut);
  active_tool->preserve = FALSE;
}

static void
levels_value_callback (GtkWidget *w,
		       gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;

  if (ld->channel != HISTOGRAM_VALUE)
    {
      ld->channel = HISTOGRAM_VALUE;
      histogram_widget_channel (ld->histogram, ld->channel);
      levels_update (ld, ALL);
    }
}

static void
levels_red_callback (GtkWidget *w,
		     gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;

  if (ld->channel != HISTOGRAM_RED)
    {
      ld->channel = HISTOGRAM_RED;
      histogram_widget_channel (ld->histogram, ld->channel);
      levels_update (ld, ALL);
    }
}

static void
levels_green_callback (GtkWidget *w,
		       gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;

  if (ld->channel != HISTOGRAM_GREEN)
    {
      ld->channel = HISTOGRAM_GREEN;
      histogram_widget_channel (ld->histogram, ld->channel);
      levels_update (ld, ALL);
    }
}

static void
levels_blue_callback (GtkWidget *w,
		      gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;

  if (ld->channel != HISTOGRAM_BLUE)
    {
      ld->channel = HISTOGRAM_BLUE;
      histogram_widget_channel (ld->histogram, ld->channel);
      levels_update (ld, ALL);
    }
}

static void
levels_alpha_callback (GtkWidget *w,
		      gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;

  if (ld->channel != HISTOGRAM_ALPHA)
    {
      ld->channel = HISTOGRAM_ALPHA;
      histogram_widget_channel (ld->histogram, ld->channel);
      levels_update (ld, ALL);
    }
}

static void
levels_adjust_channel (LevelsDialog    *ld,
		       GimpHistogram   *hist,
		       int              channel)
{
  int i;
  double count, new_count, percentage, next_percentage;

  ld->gamma[channel]       = 1.0;
  ld->low_output[channel]  = 0;
  ld->high_output[channel] = 255;

  
  count = gimp_histogram_get_count(hist, 0, 255);

  if (count == 0.0)
    {
      ld->low_input[channel] = 0;
      ld->high_input[channel] = 0;
    }
  else
    {
      /*  Set the low input  */
      new_count = 0.0;
      for (i = 0; i < 255; i++)
	{
	  new_count += gimp_histogram_get_value(hist, channel, i);
	  percentage = new_count / count;
	  next_percentage = (new_count + gimp_histogram_get_value(hist,
								  channel,
								  i + 1)) /
	    count;
	  if (fabs (percentage - 0.006) < fabs (next_percentage - 0.006))
	    {
	      ld->low_input[channel] = i + 1;
	      break;
	    }
	}
      /*  Set the high input  */
      new_count = 0.0;
      for (i = 255; i > 0; i--)
	{
	  new_count += gimp_histogram_get_value(hist, channel, i);
	  percentage = new_count / count;
	  next_percentage = (new_count + gimp_histogram_get_value(hist,
								  channel,
							      i - 1)) / count;
	  if (fabs (percentage - 0.006) < fabs (next_percentage - 0.006))
	    {
	      ld->high_input[channel] = i - 1;
	      break;
	    }
	}
    }
}

static void
levels_auto_levels_callback (GtkWidget *widget,
			     gpointer   client_data)
{
  LevelsDialog *ld;
  int channel;

  ld = (LevelsDialog *) client_data;

  if (ld->color)
    {
      /*  Set the overall value to defaults  */
      ld->low_input[HISTOGRAM_VALUE]   = 0;
      ld->gamma[HISTOGRAM_VALUE]       = 1.0;
      ld->high_input[HISTOGRAM_VALUE]  = 255;
      ld->low_output[HISTOGRAM_VALUE]  = 0;
      ld->high_output[HISTOGRAM_VALUE] = 255;

      for (channel = 0; channel < 3; channel ++)
	levels_adjust_channel (ld, ld->hist, channel + 1);
    }
  else
    levels_adjust_channel (ld, ld->hist, HISTOGRAM_VALUE);

  levels_update (ld, ALL);
  if (ld->preview)
    levels_preview (ld);
}

static void
levels_ok_callback (GtkWidget *widget,
		    gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;

  if (GTK_WIDGET_VISIBLE (ld->shell))
    gtk_widget_hide (ld->shell);

  active_tool->preserve = TRUE;

  if (!ld->preview)
  {
    levels_lut_setup(ld->lut, ld->gamma, ld->low_input, ld->high_input,
		     ld->low_output, ld->high_output,
		     gimp_drawable_bytes(ld->drawable));
    image_map_apply (ld->image_map, (ImageMapApplyFunc)gimp_lut_process_2,
		     (void *) ld->lut);
  }

  if (ld->image_map)
    image_map_commit (ld->image_map);

  active_tool->preserve = FALSE;

  ld->image_map = NULL;
}

static gint
levels_delete_callback (GtkWidget *w,
			GdkEvent *e,
			gpointer client_data)
{
  levels_cancel_callback (w, client_data);

  return TRUE;
}

static void
levels_cancel_callback (GtkWidget *widget,
			gpointer   client_data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) client_data;
  if (GTK_WIDGET_VISIBLE (ld->shell))
    gtk_widget_hide (ld->shell);

  if (ld->image_map)
    {
      active_tool->preserve = TRUE;
      image_map_abort (ld->image_map);
      active_tool->preserve = FALSE;

      ld->image_map = NULL;
      gdisplays_flush ();
    }

}

static void
levels_preview_update (GtkWidget *w,
		       gpointer   data)
{
  LevelsDialog *ld;

  ld = (LevelsDialog *) data;

  if (GTK_TOGGLE_BUTTON (w)->active)
    {
      ld->preview = TRUE;
      levels_preview (ld);
    }
  else
    ld->preview = FALSE;
}

static void
levels_low_input_spin_update (GtkWidget *w,
			      gpointer   data)
{
  LevelsDialog *ld;
  int value;

  ld = (LevelsDialog *) data;
  value = gtk_spin_button_get_value_as_int (GTK_SPIN_BUTTON (ld->low_input_spin));
  value = BOUNDS (value, 0, ld->high_input[ld->channel]);
  /*  enforce a consistent displayed value (low_input <= high_input)  */
  gtk_spin_button_set_value(GTK_SPIN_BUTTON (ld->low_input_spin), value);

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

      if (ld->preview)
	levels_preview (ld);
    }
}

static void
levels_gamma_text_update (GtkWidget *w,
			  gpointer   data)
{
  LevelsDialog *ld;
  char *str;
  double value;

  str = gtk_entry_get_text (GTK_ENTRY (w));
  ld = (LevelsDialog *) data;
  value = BOUNDS ((atof (str)), 0.1, 10.0);

  if (value != ld->gamma[ld->channel])
    {
      ld->gamma[ld->channel] = value;
      levels_update (ld, INPUT_LEVELS | INPUT_SLIDERS | DRAW);

      if (ld->preview)
	levels_preview (ld);
    }
}

static void
levels_high_input_spin_update (GtkWidget *w,
			       gpointer   data)
{
  LevelsDialog *ld;
  int value;

  ld = (LevelsDialog *) data;
  value = gtk_spin_button_get_value_as_int (GTK_SPIN_BUTTON (ld->high_input_spin));
  value = BOUNDS (value, ld->low_input[ld->channel], 255);
  /*  enforce a consistent displayed value (high_input >= low_input)  */
   gtk_spin_button_set_value(GTK_SPIN_BUTTON (ld->high_input_spin), value);

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

      if (ld->preview)
	levels_preview (ld);
    }
}

static void
levels_low_output_spin_update (GtkWidget *w,
			       gpointer   data)
{
  LevelsDialog *ld;
  int value;

  ld = (LevelsDialog *) data;
  value = gtk_spin_button_get_value_as_int (GTK_SPIN_BUTTON (ld->low_output_spin));
  value = BOUNDS (value, 0, 255);

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

      if (ld->preview)
	levels_preview (ld);
    }
}

static void
levels_high_output_spin_update (GtkWidget *w,
				gpointer   data)
{
  LevelsDialog *ld;
  int value;

  ld = (LevelsDialog *) data;
  value = gtk_spin_button_get_value_as_int (GTK_SPIN_BUTTON (ld->high_output_spin));
  value = BOUNDS (value, 0, 255);

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

      if (ld->preview)
	levels_preview (ld);
    }
}

static gint
levels_input_da_events (GtkWidget    *widget,
			GdkEvent     *event,
			LevelsDialog *ld)
{
  GdkEventButton *bevent;
  GdkEventMotion *mevent;
  char text[12];
  double width, mid, tmp;
  int x, distance;
  int i;
  int update = FALSE;

  switch (event->type)
    {
    case GDK_EXPOSE:
      if (widget == ld->input_levels_da[1])
	levels_update (ld, INPUT_SLIDERS);
      break;

    case GDK_BUTTON_PRESS:
      gtk_grab_add (widget);
      bevent = (GdkEventButton *) event;

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

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

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

      if (ld->preview)
	levels_preview (ld);
      break;

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

    default:
      break;
    }

  if (update)
    {
      switch (ld->active_slider)
	{
	case 0:  /*  low input  */
	  ld->low_input[ld->channel] = ((double) x / (double) DA_WIDTH) * 255.0;
	  ld->low_input[ld->channel] = BOUNDS (ld->low_input[ld->channel], 0,
					       ld->high_input[ld->channel]);
	  break;

	case 1:  /*  gamma  */
	  width = (double) (ld->slider_pos[2] - ld->slider_pos[0]) / 2.0;
	  mid = ld->slider_pos[0] + width;

	  x = BOUNDS (x, ld->slider_pos[0], ld->slider_pos[2]);
	  tmp = (double) (x - mid) / width;
	  ld->gamma[ld->channel] = 1.0 / pow (10, tmp);

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

	case 2:  /*  high input  */
	  ld->high_input[ld->channel] = ((double) x / (double) DA_WIDTH) * 255.0;
	  ld->high_input[ld->channel] = BOUNDS (ld->high_input[ld->channel],
						ld->low_input[ld->channel], 255);
	  break;
	}

      levels_update (ld, INPUT_SLIDERS | INPUT_LEVELS | DRAW);
    }

  return FALSE;
}

static gint
levels_output_da_events (GtkWidget    *widget,
			 GdkEvent     *event,
			 LevelsDialog *ld)
{
  GdkEventButton *bevent;
  GdkEventMotion *mevent;
  int x, distance;
  int i;
  int update = FALSE;

  switch (event->type)
    {
    case GDK_EXPOSE:
      if (widget == ld->output_levels_da[1])
	levels_update (ld, OUTPUT_SLIDERS);
      break;


    case GDK_BUTTON_PRESS:
      bevent = (GdkEventButton *) event;

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

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

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

      if (ld->preview)
	levels_preview (ld);
      break;

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

    default:
      break;
    }

  if (update)
    {
      switch (ld->active_slider)
	{
	case 3:  /*  low output  */
	  ld->low_output[ld->channel] = ((double) x / (double) DA_WIDTH) * 255.0;
	  ld->low_output[ld->channel] = BOUNDS (ld->low_output[ld->channel], 0, 255);
	  break;

	case 4:  /*  high output  */
	  ld->high_output[ld->channel] = ((double) x / (double) DA_WIDTH) * 255.0;
	  ld->high_output[ld->channel] = BOUNDS (ld->high_output[ld->channel], 0, 255);
	  break;
	}

      levels_update (ld, OUTPUT_SLIDERS | DRAW);
    }

  return FALSE;
}