negadoctor.c

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/*
    This file is part of the Ansel project.
    Copyright (C) 2020 Aldric Renaudin.
    Copyright (C) 2020, 2022-2023, 2025-2026 Aurélien PIERRE.
    Copyright (C) 2020-2022 Diederik Ter Rahe.
    Copyright (C) 2020, 2022 Pascal Obry.
    Copyright (C) 2020-2021 Ralf Brown.
    Copyright (C) 2020 Tobias Ellinghaus.
    Copyright (C) 2021 Chris Elston.
    Copyright (C) 2021 Dan Torop.
    Copyright (C) 2021 Hubert Kowalski.
    Copyright (C) 2022 Hanno Schwalm.
    Copyright (C) 2022 Martin Bařinka.
    Copyright (C) 2022 Philipp Lutz.
    Copyright (C) 2023, 2025 Guillaume Stutin.
    Copyright (C) 2023 Luca Zulberti.
    
    Ansel 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.
    
    Ansel 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 Ansel.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "bauhaus/bauhaus.h"
#include "common/darktable.h"
#include "common/opencl.h"
#include "control/control.h"
#include "develop/develop.h"
#include "develop/imageop.h"
#include "develop/imageop_math.h"
#include "develop/imageop_gui.h"
#include "develop/openmp_maths.h"
#include "dtgtk/button.h"
#include "dtgtk/resetlabel.h"
 
#include "gui/gtk.h"
#include "gui/presets.h"
#include "gui/color_picker_proxy.h"
#include "iop/iop_api.h"
 
#include <glib.h>
#include <math.h>
#include <stdlib.h>
 
 #define THRESHOLD 2.3283064365386963e-10f // -32 EV
 
 
DT_MODULE_INTROSPECTION(2, dt_iop_negadoctor_params_t)
 
 
typedef enum dt_iop_negadoctor_filmstock_t
{
  // What kind of emulsion are we working on ?
  DT_FILMSTOCK_NB = 0,   // $DESCRIPTION: "black and white film"
  DT_FILMSTOCK_COLOR = 1 // $DESCRIPTION: "color film"
} dt_iop_negadoctor_filmstock_t;
 
 
typedef struct dt_iop_negadoctor_params_t
{
  dt_iop_negadoctor_filmstock_t film_stock; /* $DEFAULT: DT_FILMSTOCK_COLOR $DESCRIPTION: "film stock" */
  float Dmin[4];                            /* color of film substrate
                                               $MIN: 0.00001 $MAX: 1.5 $DEFAULT: 1.0 */
  float wb_high[4];                         /* white balance RGB coeffs (illuminant)
                                               $MIN: 0.25 $MAX: 2 $DEFAULT: 1.0 */
  float wb_low[4];                          /* white balance RGB offsets (base light)
                                               $MIN: 0.25 $MAX: 2 $DEFAULT: 1.0 */
  float D_max;                              /* max density of film
                                               $MIN: 0.1 $MAX: 6 $DEFAULT: 2.046 */
  float offset;                             /* inversion offset
                                               $MIN: -1.0 $MAX: 1.0 $DEFAULT: -0.05 $DESCRIPTION: "scan exposure bias" */
  float black;                              /* display black level
                                               $MIN: -0.5 $MAX: 0.5 $DEFAULT: 0.0755 $DESCRIPTION: "paper black (density correction)" */
  float gamma;                              /* display gamma
                                               $MIN: 1.0 $MAX: 8.0 $DEFAULT: 4.0 $DESCRIPTION: "paper grade (gamma)" */
  float soft_clip;                          /* highlights roll-off
                                               $MIN: 0.0001 $MAX: 1.0 $DEFAULT: 0.75 $DESCRIPTION: "paper gloss (specular highlights)" */
  float exposure;                           /* extra exposure
                                               $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.9245 $DESCRIPTION: "print exposure adjustment" */
} dt_iop_negadoctor_params_t;
 
 
typedef struct dt_iop_negadoctor_data_t
{
  dt_aligned_pixel_t Dmin;                // color of film substrate
  dt_aligned_pixel_t wb_high;             // white balance RGB coeffs / Dmax
  dt_aligned_pixel_t offset;              // inversion offset
  float black;                            // display black level
  float gamma;                            // display gamma
  float soft_clip;                        // highlights roll-off
  float soft_clip_comp;                   // 1 - softclip, complement to 1
  float exposure;                         // extra exposure
} dt_iop_negadoctor_data_t;
 
 
typedef struct dt_iop_negadoctor_gui_data_t
{
  GtkNotebook *notebook;
  GtkWidget *film_stock;
  GtkWidget *Dmin_R, *Dmin_G, *Dmin_B;
  GtkWidget *wb_high_R, *wb_high_G, *wb_high_B;
  GtkWidget *wb_low_R, *wb_low_G, *wb_low_B;
  GtkWidget *D_max;
  GtkWidget *offset;
  GtkWidget *black, *gamma, *soft_clip, *exposure;
  GtkWidget *Dmin_picker, *Dmin_sampler;
  GtkWidget *WB_high_picker, *WB_high_norm, *WB_high_sampler;
  GtkWidget *WB_low_picker, *WB_low_norm, *WB_low_sampler;
} dt_iop_negadoctor_gui_data_t;
 
 
typedef struct dt_iop_negadoctor_global_data_t
{
  int kernel_negadoctor;
} dt_iop_negadoctor_global_data_t;
 
 
const char *name()
{
  return _("ne_gadoctor");
}
 
const char *aliases()
{
  return _("film|invert|negative|scan");
}
 
const char **description(struct dt_iop_module_t *self)
{
  return dt_iop_set_description(self, _("invert film negative scans and simulate printing on paper"),
                                      _("corrective and creative"),
                                      _("linear, RGB, display-referred"),
                                      _("non-linear, RGB"),
                                      _("non-linear, RGB, display-referred"));
}
 
int flags()
{
  return IOP_FLAGS_INCLUDE_IN_STYLES | IOP_FLAGS_ALLOW_TILING | IOP_FLAGS_ONE_INSTANCE;
}
 
 
int default_group()
{
  return IOP_GROUP_FILM;
}
 
 
int default_colorspace(dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, const dt_dev_pixelpipe_iop_t *piece)
{
  return IOP_CS_RGB;
}
 
int legacy_params(dt_iop_module_t *self, const void *const old_params, const int old_version,
                  void *new_params, const int new_version)
{
  if(old_version == 1 && new_version == 2)
  {
    typedef struct dt_iop_negadoctor_params_v1_t
    {
      dt_iop_negadoctor_filmstock_t film_stock;
      dt_aligned_pixel_t Dmin;                // color of film substrate
      dt_aligned_pixel_t wb_high;             // white balance RGB coeffs (illuminant)
      dt_aligned_pixel_t wb_low;              // white balance RGB offsets (base light)
      float D_max;                            // max density of film
      float offset;                           // inversion offset
      float black;                            // display black level
      float gamma;                            // display gamma
      float soft_clip;                        // highlights roll-off
      float exposure;                         // extra exposure
    } dt_iop_negadoctor_params_v1_t;
 
    dt_iop_negadoctor_params_v1_t *o = (dt_iop_negadoctor_params_v1_t *)old_params;
    dt_iop_negadoctor_params_t *n = (dt_iop_negadoctor_params_t *)new_params;
    dt_iop_negadoctor_params_t *d = (dt_iop_negadoctor_params_t *)self->default_params;
 
    *n = *d; // start with a fresh copy of default parameters
 
    // WARNING: when copying the arrays in a for loop, gcc wrongly assumed
    //          that n and o were aligned and used AVX instructions for me,
    //          which segfaulted. let's hope this doesn't get optimized too much.
    n->film_stock = o->film_stock;
    n->Dmin[0] = o->Dmin[0];
    n->Dmin[1] = o->Dmin[1];
    n->Dmin[2] = o->Dmin[2];
    n->Dmin[3] = o->Dmin[3];
    n->wb_high[0] = o->wb_high[0];
    n->wb_high[1] = o->wb_high[1];
    n->wb_high[2] = o->wb_high[2];
    n->wb_high[3] = o->wb_high[3];
    n->wb_low[0] = o->wb_low[0];
    n->wb_low[1] = o->wb_low[1];
    n->wb_low[2] = o->wb_low[2];
    n->wb_low[3] = o->wb_low[3];
    n->D_max = o->D_max;
    n->offset = o->offset;
    n->black = o->black;
    n->gamma = o->gamma;
    n->soft_clip = o->soft_clip;
    n->exposure = o->exposure;
 
    return 0;
  }
  return 1;
}
 
void commit_params(dt_iop_module_t *self, dt_iop_params_t *p1, dt_dev_pixelpipe_t *pipe,
                   dt_dev_pixelpipe_iop_t *piece)
{
  const dt_iop_negadoctor_params_t *const p = (dt_iop_negadoctor_params_t *)p1;
  dt_iop_negadoctor_data_t *const d = (dt_iop_negadoctor_data_t *)piece->data;
 
  // keep WB_high even in B&W mode to apply sepia or warm tone look
  // but premultiply it aheard with Dmax to spare one div per pixel
  for(size_t c = 0; c < 4; c++) d->wb_high[c] = p->wb_high[c] / p->D_max;
 
  for(size_t c = 0; c < 4; c++) d->offset[c] = p->wb_high[c] * p->offset * p->wb_low[c];
 
  // ensure we use a monochrome Dmin for B&W film
  if(p->film_stock == DT_FILMSTOCK_COLOR)
    for(size_t c = 0; c < 4; c++) d->Dmin[c] = p->Dmin[c];
  else if(p->film_stock == DT_FILMSTOCK_NB)
    for(size_t c = 0; c < 4; c++) d->Dmin[c] = p->Dmin[0];
 
  // arithmetic trick allowing to rewrite the pixel inversion as FMA
  d->black = -p->exposure * (1.0f + p->black);
 
  // highlights soft clip
  d->soft_clip = p->soft_clip;
  d->soft_clip_comp = 1.0f - p->soft_clip;
 
  // copy
  d->exposure = p->exposure;
  d->gamma = p->gamma;
}
 
 
__DT_CLONE_TARGETS__
int process(struct dt_iop_module_t *const self, const dt_dev_pixelpipe_t *const pipe,
            const dt_dev_pixelpipe_iop_t *const piece, const void *const restrict ivoid,
            void *const restrict ovoid)
{
  const dt_iop_roi_t *const restrict roi_out = &piece->roi_out;
  const dt_iop_negadoctor_data_t *const d = piece->data;
  const float *const restrict in = (float *)ivoid;
  float *const restrict out = (float *)ovoid;
  __OMP_FOR_SIMD__(aligned(in, out:64) collapse(2))
  for(size_t k = 0; k < (size_t)roi_out->height * roi_out->width * 4; k += 4)
  {
    for(size_t c = 0; c < 4; c++)
    {
      // Unpack vectors one by one with extra pragmas to be sure the compiler understands they can be vectorized
      const float *const restrict pix_in = in + k;
      float *const restrict pix_out = out + k;
      const float *const restrict Dmin = __builtin_assume_aligned(d->Dmin, 16);
      const float *const restrict wb_high = __builtin_assume_aligned(d->wb_high, 16);
      const float *const restrict offset = __builtin_assume_aligned(d->offset, 16);
 
      // Convert transmission to density using Dmin as a fulcrum
      const float density = - log10f(Dmin[c] / fmaxf(pix_in[c], THRESHOLD)); // threshold to -32 EV
 
      // Correct density in log space
      const float corrected_de = wb_high[c] * density + offset[c];
 
      // Print density on paper : ((1 - 10^corrected_de + black) * exposure)^gamma rewritten for FMA
      const float print_linear = -(d->exposure * fast_exp10f(corrected_de) + d->black);
      const float print_gamma = powf(fmaxf(print_linear, 0.0f), d->gamma); // note : this is always > 0
 
      // Compress highlights. from https://lists.gnu.org/archive/html/openexr-devel/2005-03/msg00009.html
      pix_out[c] =  (print_gamma > d->soft_clip) ? d->soft_clip + (1.0f - fast_expf(-(print_gamma - d->soft_clip) / d->soft_clip_comp)) * d->soft_clip_comp
                                                 : print_gamma;
    }
  }
 
  if(pipe->mask_display & DT_DEV_PIXELPIPE_DISPLAY_MASK)
    dt_iop_alpha_copy(ivoid, ovoid, roi_out->width, roi_out->height);
  return 0;
}
 
 
#ifdef HAVE_OPENCL
int process_cl(struct dt_iop_module_t *const self, const dt_dev_pixelpipe_t *const pipe,
               const dt_dev_pixelpipe_iop_t *const piece, cl_mem dev_in, cl_mem dev_out)
{
  const dt_iop_roi_t *const restrict roi_in = &piece->roi_in;
  const dt_iop_negadoctor_data_t *const d = (dt_iop_negadoctor_data_t *)piece->data;
  const dt_iop_negadoctor_global_data_t *const gd = (dt_iop_negadoctor_global_data_t *)self->global_data;
 
  cl_int err = -999;
 
  const int devid = pipe->devid;
  const int width = roi_in->width;
  const int height = roi_in->height;
 
  size_t sizes[] = { ROUNDUPDWD(width, devid), ROUNDUPDHT(height, devid), 1 };
 
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 0, sizeof(cl_mem), (void *)&dev_in);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 1, sizeof(cl_mem), (void *)&dev_out);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 2, sizeof(int), (void *)&width);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 3, sizeof(int), (void *)&height);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 4, 4 * sizeof(float), (void *)&d->Dmin);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 5, 4 * sizeof(float), (void *)&d->wb_high);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 6, 4 * sizeof(float), (void *)&d->offset);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 7, sizeof(float), (void *)&d->exposure);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 8, sizeof(float), (void *)&d->black);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 9, sizeof(float), (void *)&d->gamma);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 10, sizeof(float), (void *)&d->soft_clip);
  dt_opencl_set_kernel_arg(devid, gd->kernel_negadoctor, 11, sizeof(float), (void *)&d->soft_clip_comp);
 
  err = dt_opencl_enqueue_kernel_2d(devid, gd->kernel_negadoctor, sizes);
  if(err != CL_SUCCESS) goto error;
    return TRUE;
 
error:
  dt_print(DT_DEBUG_OPENCL, "[opencl_negadoctor] couldn't enqueue kernel! %d\n", err);
  return FALSE;
}
#endif
 
 
void init(dt_iop_module_t *module)
{
  dt_iop_default_init(module);
 
  dt_iop_negadoctor_params_t *d = module->default_params;
 
  d->Dmin[0] = 1.00f;
  d->Dmin[1] = 0.45f;
  d->Dmin[2] = 0.25f;
}
 
void init_presets(dt_iop_module_so_t *self)
{
  dt_iop_negadoctor_params_t tmp = (dt_iop_negadoctor_params_t){ .film_stock = DT_FILMSTOCK_COLOR,
                                                                 .Dmin = { 1.13f, 0.49f, 0.27f, 0.0f},
                                                                 .wb_high = { 1.0f, 1.0f, 1.0f, 0.0f },
                                                                 .wb_low = { 1.0f, 1.0f, 1.0f, 0.0f },
                                                                 .D_max = 1.6f,
                                                                 .offset = -0.05f,
                                                                 .gamma = 4.0f,
                                                                 .soft_clip = 0.75f,
                                                                 .exposure = 0.9245f,
                                                                 .black = 0.0755f };
 
 
  dt_gui_presets_add_generic(_("color film"), self->op,
                             self->version(), &tmp, sizeof(tmp), 1, DEVELOP_BLEND_CS_RGB_DISPLAY);
 
  dt_iop_negadoctor_params_t tmq = (dt_iop_negadoctor_params_t){ .film_stock = DT_FILMSTOCK_NB,
                                                                 .Dmin = { 1.0f, 1.0f, 1.0f, 0.0f},
                                                                 .wb_high = { 1.0f, 1.0f, 1.0f, 0.0f },
                                                                 .wb_low = { 1.0f, 1.0f, 1.0f, 0.0f },
                                                                 .D_max = 2.2f,
                                                                 .offset = -0.05f,
                                                                 .gamma = 5.0f,
                                                                 .soft_clip = 0.75f,
                                                                 .exposure = 1.f,
                                                                 .black = 0.0755f };
 
 
  dt_gui_presets_add_generic(_("black and white film"), self->op,
                             self->version(), &tmq, sizeof(tmq), 1, DEVELOP_BLEND_CS_RGB_DISPLAY);
}
 
void init_global(dt_iop_module_so_t *module)
{
  dt_iop_negadoctor_global_data_t *gd
      = (dt_iop_negadoctor_global_data_t *)calloc(1, sizeof(dt_iop_negadoctor_global_data_t));
  if(IS_NULL_PTR(gd)) return;
 
  module->data = gd;
  const int program = 30; // negadoctor.cl, from programs.conf
  gd->kernel_negadoctor = dt_opencl_create_kernel(program, "negadoctor");
}
 
void cleanup_global(dt_iop_module_so_t *module)
{
  dt_iop_negadoctor_global_data_t *gd = module->data;
  dt_opencl_free_kernel(gd->kernel_negadoctor);
  dt_free(module->data);
}
 
void init_pipe(struct dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, dt_dev_pixelpipe_iop_t *piece)
{
  piece->data = dt_calloc_align(sizeof(dt_iop_negadoctor_data_t));
  piece->data_size = sizeof(dt_iop_negadoctor_data_t);
}
 
void cleanup_pipe(struct dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, dt_dev_pixelpipe_iop_t *piece)
{
  dt_free_align(piece->data);
  piece->data = NULL;
}
 
 
/* Global GUI stuff */
 
static void setup_color_variables(dt_iop_negadoctor_gui_data_t *const g, const gint state)
{
  gtk_widget_set_visible(g->Dmin_G, state);
  gtk_widget_set_visible(g->Dmin_B, state);
}
 
 
static void toggle_stock_controls(dt_iop_module_t *const self)
{
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  const dt_iop_negadoctor_params_t *const p = (dt_iop_negadoctor_params_t *)self->params;
 
  if(p->film_stock == DT_FILMSTOCK_NB)
  {
    // Hide color controls
    setup_color_variables(g, FALSE);
    dt_bauhaus_widget_set_label(g->Dmin_R, N_("D min"));
  }
  else if(p->film_stock == DT_FILMSTOCK_COLOR)
  {
    // Show color controls
    setup_color_variables(g, TRUE);
    dt_bauhaus_widget_set_label(g->Dmin_R, N_("D min red component"));
  }
  else
  {
    // We shouldn't be there
    fprintf(stderr, "negadoctor film stock: undefined behaviour\n");
  }
}
 
 
static void Dmin_picker_update(dt_iop_module_t *self)
{
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  const dt_iop_negadoctor_params_t *const p = (dt_iop_negadoctor_params_t *)self->params;
 
  GdkRGBA color;
  color.alpha = 1.0f;
 
  if(p->film_stock == DT_FILMSTOCK_COLOR)
  {
    color.red = p->Dmin[0];
    color.green = p->Dmin[1];
    color.blue = p->Dmin[2];
  }
  else if(p->film_stock == DT_FILMSTOCK_NB)
  {
    color.red = color.green = color.blue = p->Dmin[0];
  }
 
  gtk_color_chooser_set_rgba(GTK_COLOR_CHOOSER(g->Dmin_picker), &color);
}
 
static void Dmin_picker_callback(GtkColorButton *widget, dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_iop_color_picker_reset(self, TRUE);
 
  GdkRGBA c;
  gtk_color_chooser_get_rgba(GTK_COLOR_CHOOSER(widget), &c);
  p->Dmin[0] = c.red;
  p->Dmin[1] = c.green;
  p->Dmin[2] = c.blue;
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->Dmin_R, p->Dmin[0]);
  dt_bauhaus_slider_set(g->Dmin_G, p->Dmin[1]);
  dt_bauhaus_slider_set(g->Dmin_B, p->Dmin[2]);
  --darktable.gui->reset;
 
  Dmin_picker_update(self);
  dt_iop_color_picker_reset(self, TRUE);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
static void WB_low_picker_update(dt_iop_module_t *self)
{
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  const dt_iop_negadoctor_params_t *const p = (dt_iop_negadoctor_params_t *)self->params;
 
  GdkRGBA color;
  color.alpha = 1.0f;
 
  dt_aligned_pixel_t WB_low_invert;
  for(size_t c = 0; c < 3; ++c) WB_low_invert[c] = 2.0f - p->wb_low[c];
  const float WB_low_max = v_maxf(WB_low_invert);
  for(size_t c = 0; c < 3; ++c) WB_low_invert[c] /= WB_low_max;
 
  color.red = WB_low_invert[0];
  color.green = WB_low_invert[1];
  color.blue = WB_low_invert[2];
 
  gtk_color_chooser_set_rgba(GTK_COLOR_CHOOSER(g->WB_low_picker), &color);
}
 
static void WB_low_picker_callback(GtkColorButton *widget, dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_iop_color_picker_reset(self, TRUE);
 
  GdkRGBA c;
  gtk_color_chooser_get_rgba(GTK_COLOR_CHOOSER(widget), &c);
 
  dt_aligned_pixel_t RGB = { 2.0f - c.red, 2.0f - c.green, 2.0f - c.blue };
 
  float RGB_min = v_minf(RGB);
  for(size_t k = 0; k < 3; k++) p->wb_low[k] = RGB[k] / RGB_min;
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->wb_low_R, p->wb_low[0]);
  dt_bauhaus_slider_set(g->wb_low_G, p->wb_low[1]);
  dt_bauhaus_slider_set(g->wb_low_B, p->wb_low[2]);
  --darktable.gui->reset;
 
  WB_low_picker_update(self);
  dt_iop_color_picker_reset(self, TRUE);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
 
static void WB_high_picker_update(dt_iop_module_t *self)
{
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  const dt_iop_negadoctor_params_t *const p = (dt_iop_negadoctor_params_t *)self->params;
 
  GdkRGBA color;
  color.alpha = 1.0f;
 
  dt_aligned_pixel_t WB_high_invert;
  for(size_t c = 0; c < 3; ++c) WB_high_invert[c] = 2.0f - p->wb_high[c];
  const float WB_high_max = v_maxf(WB_high_invert);
  for(size_t c = 0; c < 3; ++c) WB_high_invert[c] /= WB_high_max;
 
  color.red = WB_high_invert[0];
  color.green = WB_high_invert[1];
  color.blue = WB_high_invert[2];
 
  gtk_color_chooser_set_rgba(GTK_COLOR_CHOOSER(g->WB_high_picker), &color);
}
 
static void WB_high_picker_callback(GtkColorButton *widget, dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_iop_color_picker_reset(self, TRUE);
 
  GdkRGBA c;
  gtk_color_chooser_get_rgba(GTK_COLOR_CHOOSER(widget), &c);
 
  dt_aligned_pixel_t RGB = { 2.0f - c.red, 2.0f - c.green, 2.0f - c.blue };
  float RGB_min = v_minf(RGB);
  for(size_t k = 0; k < 3; k++) p->wb_high[k] = RGB[k] / RGB_min;
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->wb_high_R, p->wb_high[0]);
  dt_bauhaus_slider_set(g->wb_high_G, p->wb_high[1]);
  dt_bauhaus_slider_set(g->wb_high_B, p->wb_high[2]);
  --darktable.gui->reset;
 
  WB_high_picker_update(self);
  dt_iop_color_picker_reset(self, TRUE);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
static void Wb_low_norm_callback(GtkColorButton *widget, dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
 
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
 
  const float WB_low_max = v_maxf(p->wb_low);
  for(size_t c = 0; c < 3; ++c)
    p->wb_low[c] /= WB_low_max;
 
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->wb_low_R, p->wb_low[0]);
  dt_bauhaus_slider_set(g->wb_low_G, p->wb_low[1]);
  dt_bauhaus_slider_set(g->wb_low_B, p->wb_low[2]);
  --darktable.gui->reset;
 
  WB_low_picker_update(self);
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
static void Wb_high_norm_callback(GtkColorButton *widget, dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
 
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  const float WB_high_min = v_minf(p->wb_high);
  for(size_t c = 0; c < 3; ++c)
    p->wb_high[c] /= WB_high_min;
 
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->wb_high_R, p->wb_high[0]);
  dt_bauhaus_slider_set(g->wb_high_G, p->wb_high[1]);
  dt_bauhaus_slider_set(g->wb_high_B, p->wb_high[2]);
  --darktable.gui->reset;
 
  WB_low_picker_update(self);
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
/* Color pickers auto-tuners */
 
// measure Dmin from the film edges first
static void apply_auto_Dmin(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  for(int k = 0; k < 4; k++) p->Dmin[k] = self->picked_color[k];
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->Dmin_R, p->Dmin[0]);
  dt_bauhaus_slider_set(g->Dmin_G, p->Dmin[1]);
  dt_bauhaus_slider_set(g->Dmin_B, p->Dmin[2]);
  --darktable.gui->reset;
 
  Dmin_picker_update(self);
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
// from Dmin, find out the range of density values of the film and compute Dmax
static void apply_auto_Dmax(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_aligned_pixel_t RGB;
  for(int c = 0; c < 3; c++)
  {
    RGB[c] = log10f(p->Dmin[c] / fmaxf(self->picked_color_min[c], THRESHOLD));
  }
 
  // Take the max(RGB) for safety. Big values unclip whites
  p->D_max = v_maxf(RGB);
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->D_max, p->D_max);
  --darktable.gui->reset;
 
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
// from Dmax, compute the offset so the range of density is rescaled between [0; 1]
static void apply_auto_offset(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_aligned_pixel_t RGB;
  for(int c = 0; c < 3; c++)
    RGB[c] = log10f(p->Dmin[c] / fmaxf(self->picked_color_max[c], THRESHOLD)) / p->D_max;
 
  // Take the min(RGB) for safety. Negative values unclip blacks
  p->offset = v_minf(RGB);
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->offset, p->offset);
  --darktable.gui->reset;
 
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
// from Dmax and offset, compute the white balance correction as multipliers of the offset
// such that offset x wb[c] make black monochrome
static void apply_auto_WB_low(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_aligned_pixel_t RGB_min;
  for(int c = 0; c < 3; c++)
    RGB_min[c] = log10f(p->Dmin[c] / fmaxf(self->picked_color[c], THRESHOLD)) / p->D_max;
 
  const float RGB_v_min = v_minf(RGB_min); // warning: can be negative
  for(int c = 0; c < 3; c++) p->wb_low[c] =  RGB_v_min / RGB_min[c];
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->wb_low_R, p->wb_low[0]);
  dt_bauhaus_slider_set(g->wb_low_G, p->wb_low[1]);
  dt_bauhaus_slider_set(g->wb_low_B, p->wb_low[2]);
  --darktable.gui->reset;
 
  WB_low_picker_update(self);
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
// from Dmax, offset and white balance multipliers, compute the white balance of the illuminant as multipliers of 1/Dmax
// such that WB[c] / Dmax make white monochrome
static void apply_auto_WB_high(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_aligned_pixel_t RGB_min;
  for(int c = 0; c < 3; c++)
    RGB_min[c] = fabsf(-1.0f / (p->offset * p->wb_low[c] - log10f(p->Dmin[c] / fmaxf(self->picked_color[c], THRESHOLD)) / p->D_max));
 
  const float RGB_v_min = v_minf(RGB_min); // warning : must be positive
  for(int c = 0; c < 3; c++) p->wb_high[c] = RGB_min[c] / RGB_v_min;
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->wb_high_R, p->wb_high[0]);
  dt_bauhaus_slider_set(g->wb_high_G, p->wb_high[1]);
  dt_bauhaus_slider_set(g->wb_high_B, p->wb_high[2]);
  --darktable.gui->reset;
 
  WB_high_picker_update(self);
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
// from Dmax, offset and both white balances, compute the print black adjustment
// such that the printed values range from 0 to + infinity
static void apply_auto_black(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_aligned_pixel_t RGB;
  for(int c = 0; c < 3; c++)
  {
    RGB[c] = -log10f(p->Dmin[c] / fmaxf(self->picked_color_max[c], THRESHOLD));
    RGB[c] *= p->wb_high[c] / p->D_max;
    RGB[c] += p->wb_low[c] * p->offset * p->wb_high[c];
    RGB[c] = 0.1f - (1.0f - fast_exp10f(RGB[c])); // actually, remap between -3.32 EV and infinity for safety because gamma comes later
  }
  p->black = v_maxf(RGB);
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->black, p->black);
  --darktable.gui->reset;
 
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
// from Dmax, offset, both white balances, and printblack, compute the print exposure adjustment as a scaling factor
// such that the printed values range from 0 to 1
static void apply_auto_exposure(dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_aligned_pixel_t RGB;
  for(int c = 0; c < 3; c++)
  {
    RGB[c] = -log10f(p->Dmin[c] / fmaxf(self->picked_color_min[c], THRESHOLD));
    RGB[c] *= p->wb_high[c] / p->D_max;
    RGB[c] += p->wb_low[c] * p->offset;
    RGB[c] = 0.96f / (1.0f - fast_exp10f(RGB[c]) + p->black); // actually, remap in [0; 0.96] for safety
  }
  p->exposure = v_minf(RGB);
 
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->exposure, log2f(p->exposure));
  --darktable.gui->reset;
 
  dt_control_queue_redraw_widget(self->widget);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
}
 
 
void color_picker_apply(dt_iop_module_t *self, GtkWidget *picker, dt_dev_pixelpipe_t *pipe, dt_dev_pixelpipe_iop_t *piece)
{
  (void)pipe;
  (void)piece;
  if(darktable.gui->reset) return;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
 
  if     (picker == g->Dmin_sampler)
    apply_auto_Dmin(self);
  else if(picker == g->WB_high_sampler)
    apply_auto_WB_high(self);
  else if(picker == g->offset)
    apply_auto_offset(self);
  else if(picker == g->D_max)
    apply_auto_Dmax(self);
  else if(picker == g->WB_low_sampler)
    apply_auto_WB_low(self);
  else if(picker == g->exposure)
    apply_auto_exposure(self);
  else if(picker == g->black)
    apply_auto_black(self);
  else
    fprintf(stderr, "[negadoctor] unknown color picker\n");
}
 
void gui_init(dt_iop_module_t *self)
{
  dt_iop_negadoctor_gui_data_t *g = IOP_GUI_ALLOC(negadoctor);
 
  g->notebook = dt_ui_notebook_new();
 
  // Page FILM PROPERTIES
  GtkWidget *page1 = self->widget = dt_ui_notebook_page(g->notebook, N_("film properties"), NULL);
 
  // Dmin
 
  gtk_box_pack_start(GTK_BOX(page1), dt_ui_section_label_new(_("color of the film base")), FALSE, FALSE, 0);
 
  GtkWidget *row1 = GTK_WIDGET(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING));
 
  g->Dmin_picker = gtk_color_button_new();
  gtk_color_chooser_set_use_alpha(GTK_COLOR_CHOOSER(g->Dmin_picker), FALSE);
  gtk_color_button_set_title(GTK_COLOR_BUTTON(g->Dmin_picker), _("select color of film material from a swatch"));
  gtk_box_pack_start(GTK_BOX(row1), GTK_WIDGET(g->Dmin_picker), TRUE, TRUE, 0);
  g_signal_connect(G_OBJECT(g->Dmin_picker), "color-set", G_CALLBACK(Dmin_picker_callback), self);
 
  g->Dmin_sampler = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, row1);
  gtk_widget_set_tooltip_text(g->Dmin_sampler , _("pick color of film material from image"));
 
  gtk_box_pack_start(GTK_BOX(page1), GTK_WIDGET(row1), FALSE, FALSE, 0);
 
  g->Dmin_R = dt_bauhaus_slider_from_params(self, "Dmin[0]");
  dt_bauhaus_slider_set_digits(g->Dmin_R, 4);
  dt_bauhaus_slider_set_format(g->Dmin_R, "%");
  dt_bauhaus_slider_set_factor(g->Dmin_R, 100);
  dt_bauhaus_widget_set_label(g->Dmin_R, N_("D min red component"));
  gtk_widget_set_tooltip_text(g->Dmin_R, _("adjust the color and shade of the film transparent base.\n"
                                           "this value depends on the film material, \n"
                                           "the chemical fog produced while developing the film,\n"
                                           "and the scanner white balance."));
 
  g->Dmin_G = dt_bauhaus_slider_from_params(self, "Dmin[1]");
  dt_bauhaus_slider_set_digits(g->Dmin_G, 4);
  dt_bauhaus_slider_set_format(g->Dmin_G, "%");
  dt_bauhaus_slider_set_factor(g->Dmin_G, 100);
  dt_bauhaus_widget_set_label(g->Dmin_G, N_("D min green component"));
  gtk_widget_set_tooltip_text(g->Dmin_G, _("adjust the color and shade of the film transparent base.\n"
                                           "this value depends on the film material, \n"
                                           "the chemical fog produced while developing the film,\n"
                                           "and the scanner white balance."));
 
  g->Dmin_B = dt_bauhaus_slider_from_params(self, "Dmin[2]");
  dt_bauhaus_slider_set_digits(g->Dmin_B, 4);
  dt_bauhaus_slider_set_format(g->Dmin_B, "%");
  dt_bauhaus_slider_set_factor(g->Dmin_B, 100);
  dt_bauhaus_widget_set_label(g->Dmin_B, N_("D min blue component"));
  gtk_widget_set_tooltip_text(g->Dmin_B, _("adjust the color and shade of the film transparent base.\n"
                                           "this value depends on the film material, \n"
                                           "the chemical fog produced while developing the film,\n"
                                           "and the scanner white balance."));
 
  // D max and scanner bias
 
  gtk_box_pack_start(GTK_BOX(page1), dt_ui_section_label_new(_("dynamic range of the film")), FALSE, FALSE, 0);
 
  g->D_max = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, dt_bauhaus_slider_from_params(self, "D_max"));
  dt_bauhaus_slider_set_format(g->D_max, " dB");
  gtk_widget_set_tooltip_text(g->D_max, _("maximum density of the film, corresponding to white after inversion.\n"
                                          "this value depends on the film specifications, the developing process,\n"
                                          "the dynamic range of the scene and the scanner exposure settings."));
 
  gtk_box_pack_start(GTK_BOX(page1), dt_ui_section_label_new(_("scanner exposure settings")), FALSE, FALSE, 0);
 
  g->offset = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, dt_bauhaus_slider_from_params(self, "offset"));
  dt_bauhaus_slider_set_format(g->offset, " dB");
  gtk_widget_set_tooltip_text(g->offset, _("correct the exposure of the scanner, for all RGB channels,\n"
                                           "before the inversion, so blacks are neither clipped or too pale."));
 
  // Page CORRECTIONS
  GtkWidget *page2 = self->widget = dt_ui_notebook_page(g->notebook, N_("corrections"), NULL);
 
  // WB shadows
  gtk_box_pack_start(GTK_BOX(page2), dt_ui_section_label_new(_("shadows color cast")), FALSE, FALSE, 0);
 
  GtkWidget *row3 = GTK_WIDGET(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING));
 
  g->WB_low_picker = gtk_color_button_new();
  gtk_color_chooser_set_use_alpha(GTK_COLOR_CHOOSER(g->WB_low_picker), FALSE);
  gtk_color_button_set_title(GTK_COLOR_BUTTON(g->WB_low_picker), _("select color of shadows from a swatch"));
  gtk_box_pack_start(GTK_BOX(row3), GTK_WIDGET(g->WB_low_picker), TRUE, TRUE, 0);
  g_signal_connect(G_OBJECT(g->WB_low_picker), "color-set", G_CALLBACK(WB_low_picker_callback), self);
 
  g->WB_low_norm = dt_action_button_new((dt_lib_module_t *)self, N_("normalize"), Wb_low_norm_callback, self, _("normalize shadows white balance settings"), 0, 0);
  gtk_box_pack_start(GTK_BOX(row3), GTK_WIDGET(g->WB_low_norm), FALSE, FALSE, 0);
 
  g->WB_low_sampler = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, row3);
  gtk_widget_set_tooltip_text(g->WB_low_sampler, _("pick shadows color from image"));
 
  gtk_box_pack_start(GTK_BOX(page2), GTK_WIDGET(row3), FALSE, FALSE, 0);
 
  g->wb_low_R = dt_bauhaus_slider_from_params(self, "wb_low[0]");
  dt_bauhaus_widget_set_label(g->wb_low_R, N_("shadows red offset"));
  gtk_widget_set_tooltip_text(g->wb_low_R, _("correct the color cast in shadows so blacks are\n"
                                             "truly achromatic. Setting this value before\n"
                                             "the highlights illuminant white balance will help\n"
                                             "recovering the global white balance in difficult cases."));
 
  g->wb_low_G = dt_bauhaus_slider_from_params(self, "wb_low[1]");
  dt_bauhaus_widget_set_label(g->wb_low_G, N_("shadows green offset"));
  gtk_widget_set_tooltip_text(g->wb_low_G, _("correct the color cast in shadows so blacks are\n"
                                             "truly achromatic. Setting this value before\n"
                                             "the highlights illuminant white balance will help\n"
                                             "recovering the global white balance in difficult cases."));
 
  g->wb_low_B = dt_bauhaus_slider_from_params(self, "wb_low[2]");
  dt_bauhaus_widget_set_label(g->wb_low_B, N_("shadows blue offset"));
  gtk_widget_set_tooltip_text(g->wb_low_B, _("correct the color cast in shadows so blacks are\n"
                                             "truly achromatic. Setting this value before\n"
                                             "the highlights illuminant white balance will help\n"
                                             "recovering the global white balance in difficult cases."));
 
  // WB highlights
  gtk_box_pack_start(GTK_BOX(page2), dt_ui_section_label_new(_("highlights white balance")), FALSE, FALSE, 0);
 
  GtkWidget *row2 = GTK_WIDGET(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING));
 
  g->WB_high_picker = gtk_color_button_new();
  gtk_color_chooser_set_use_alpha(GTK_COLOR_CHOOSER(g->WB_high_picker), FALSE);
  gtk_color_button_set_title(GTK_COLOR_BUTTON(g->WB_high_picker), _("select color of illuminant from a swatch"));
  gtk_box_pack_start(GTK_BOX(row2), GTK_WIDGET(g->WB_high_picker), TRUE, TRUE, 0);
  g_signal_connect(G_OBJECT(g->WB_high_picker), "color-set", G_CALLBACK(WB_high_picker_callback), self);
 
  g->WB_high_norm = dt_action_button_new((dt_lib_module_t *)self, N_("normalize"), Wb_high_norm_callback, self, _("normalize highlight white balance settings"), 0, 0);
  gtk_box_pack_start(GTK_BOX(row2), GTK_WIDGET(g->WB_high_norm), FALSE, FALSE, 0);
 
  g->WB_high_sampler = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, row2);
  gtk_widget_set_tooltip_text(g->WB_high_sampler , _("pick illuminant color from image"));
 
  gtk_box_pack_start(GTK_BOX(page2), GTK_WIDGET(row2), FALSE, FALSE, 0);
 
  g->wb_high_R = dt_bauhaus_slider_from_params(self, "wb_high[0]");
  dt_bauhaus_widget_set_label(g->wb_high_R, N_("illuminant red gain"));
  gtk_widget_set_tooltip_text(g->wb_high_R, _("correct the color of the illuminant so whites are\n"
                                              "truly achromatic. Setting this value after\n"
                                              "the shadows color cast will help\n"
                                              "recovering the global white balance in difficult cases."));
 
  g->wb_high_G = dt_bauhaus_slider_from_params(self, "wb_high[1]");
  dt_bauhaus_widget_set_label(g->wb_high_G, N_("illuminant green gain"));
  gtk_widget_set_tooltip_text(g->wb_high_G, _("correct the color of the illuminant so whites are\n"
                                              "truly achromatic. Setting this value after\n"
                                              "the shadows color cast will help\n"
                                              "recovering the global white balance in difficult cases."));
 
  g->wb_high_B = dt_bauhaus_slider_from_params(self, "wb_high[2]");
  dt_bauhaus_widget_set_label(g->wb_high_B, N_("illuminant blue gain"));
  gtk_widget_set_tooltip_text(g->wb_high_B, _("correct the color of the illuminant so whites are\n"
                                              "truly achromatic. Setting this value after\n"
                                              "the shadows color cast will help\n"
                                              "recovering the global white balance in difficult cases."));
 
  // Page PRINT PROPERTIES
  GtkWidget *page3 = self->widget = dt_ui_notebook_page(g->notebook, N_("print properties"), NULL);
 
  // print corrections
  gtk_box_pack_start(GTK_BOX(page3), dt_ui_section_label_new(_("virtual paper properties")), FALSE, FALSE, 0);
 
  g->black = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, dt_bauhaus_slider_from_params(self, "black"));
  dt_bauhaus_slider_set_digits(g->black, 4);
  dt_bauhaus_slider_set_factor(g->black, 100);
  dt_bauhaus_slider_set_format(g->black, "%");
  gtk_widget_set_tooltip_text(g->black, _("correct the density of black after the inversion,\n"
                                          "to adjust the global contrast while avoiding clipping shadows."));
 
  g->gamma = dt_bauhaus_slider_from_params(self, "gamma");
  dt_bauhaus_widget_set_label(g->gamma, N_("paper grade (gamma)"));
  gtk_widget_set_tooltip_text(g->gamma, _("select the grade of the virtual paper, which is actually\n"
                                          "equivalent to applying a gamma. it compensates the film D max\n"
                                          "and recovers the contrast. use a high grade for high D max."));
 
  g->soft_clip = dt_bauhaus_slider_from_params(self, "soft_clip");
  dt_bauhaus_slider_set_factor(g->soft_clip, 100);
  dt_bauhaus_slider_set_digits(g->soft_clip, 4);
  dt_bauhaus_slider_set_format(g->soft_clip, "%");
  gtk_widget_set_tooltip_text(g->soft_clip, _("gradually compress specular highlights past this value\n"
                                              "to avoid clipping while pushing the exposure for mid-tones.\n"
                                              "this somewhat reproduces the behaviour of matte paper."));
 
  gtk_box_pack_start(GTK_BOX(page3), dt_ui_section_label_new(_("virtual print emulation")), FALSE, FALSE, 0);
 
  g->exposure = dt_color_picker_new(self, DT_COLOR_PICKER_AREA, dt_bauhaus_slider_from_params(self, "exposure"));
  dt_bauhaus_slider_set_soft_min(g->exposure, -1.0);
  dt_bauhaus_slider_set_soft_max(g->exposure, 1.0);
  dt_bauhaus_slider_set_default(g->exposure, 0.0);
  dt_bauhaus_slider_set_format(g->exposure, _(" EV"));
  gtk_widget_set_tooltip_text(g->exposure, _("correct the printing exposure after inversion to adjust\n"
                                             "the global contrast and avoid clipping highlights."));
 
  // start building top level widget
  self->widget = gtk_box_new(GTK_ORIENTATION_VERTICAL, DT_GUI_BOX_SPACING);
 
  // Film emulsion
  g->film_stock = dt_bauhaus_combobox_from_params(self, "film_stock");
  gtk_widget_set_tooltip_text(g->film_stock, _("toggle on or off the color controls"));
 
  gtk_box_pack_start(GTK_BOX(self->widget), GTK_WIDGET(g->notebook), FALSE, FALSE, 0);
  const int active_page = dt_conf_get_int("plugins/darkroom/negadoctor/gui_page");
  gtk_widget_show(gtk_notebook_get_nth_page(g->notebook, active_page));
  gtk_notebook_set_current_page(g->notebook, active_page);
 
}
 
void gui_cleanup(struct dt_iop_module_t *self)
{
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  if(!IS_NULL_PTR(g) && GTK_IS_NOTEBOOK(g->notebook))
    dt_conf_set_int("plugins/darkroom/negadoctor/gui_page", gtk_notebook_get_current_page(g->notebook));
  IOP_GUI_FREE;
}
 
void gui_changed(dt_iop_module_t *self, GtkWidget *w, void *previous)
{
  dt_iop_negadoctor_params_t *p = (dt_iop_negadoctor_params_t *)self->params;
  dt_iop_negadoctor_gui_data_t *g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(w) || w == g->film_stock)
  {
    toggle_stock_controls(self);
    Dmin_picker_update(self);
  }
  else if(w == g->Dmin_R && p->film_stock == DT_FILMSTOCK_NB)
  {
    dt_bauhaus_slider_set(g->Dmin_G, p->Dmin[0]);
    dt_bauhaus_slider_set(g->Dmin_B, p->Dmin[0]);
  }
  else if(w == g->Dmin_R || w == g->Dmin_G || w == g->Dmin_B)
  {
    Dmin_picker_update(self);
  }
  else if(w == g->exposure)
  {
    p->exposure = powf(2.0f, p->exposure);
  }
 
  if(IS_NULL_PTR(w) || w == g->wb_high_R || w == g->wb_high_G || w == g->wb_high_B)
  {
    WB_high_picker_update(self);
  }
 
  if(IS_NULL_PTR(w) || w == g->wb_low_R || w == g->wb_low_G || w == g->wb_low_B)
  {
    WB_low_picker_update(self);
  }
}
 
 
void gui_update(dt_iop_module_t *const self)
{
  // let gui slider match current parameters:
  dt_iop_negadoctor_gui_data_t *const g = (dt_iop_negadoctor_gui_data_t *)self->gui_data;
  const dt_iop_negadoctor_params_t *const p = (dt_iop_negadoctor_params_t *)self->params;
 
  dt_iop_color_picker_reset(self, TRUE);
 
 
  dt_bauhaus_slider_set(g->exposure, log2f(p->exposure));     // warning: GUI is in EV
 
  // Update custom stuff
  gui_changed(self, NULL, NULL);
}
 
void gui_reset(dt_iop_module_t *self)
{
  dt_iop_color_picker_reset(self, TRUE);
}
// clang-format off
// modelines: These editor modelines have been set for all relevant files by tools/update_modelines.py
// vim: shiftwidth=2 expandtab tabstop=2 cindent
// kate: tab-indents: off; indent-width 2; replace-tabs on; indent-mode cstyle; remove-trailing-spaces modified;
// clang-format on