defringe.c

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/*
    This file is part of darktable,
    Copyright (C) 2013-2014 Dennis Gnad.
    Copyright (C) 2014-2016 Roman Lebedev.
    Copyright (C) 2014, 2016, 2019 Tobias Ellinghaus.
    Copyright (C) 2015 Pedro Côrte-Real.
    Copyright (C) 2016 johannes hanika.
    Copyright (C) 2017 Heiko Bauke.
    Copyright (C) 2017-2019 luzpaz.
    Copyright (C) 2017 Ulrich Pegelow.
    Copyright (C) 2018, 2020, 2023, 2025-2026 Aurélien PIERRE.
    Copyright (C) 2018 Edgardo Hoszowski.
    Copyright (C) 2018 Maurizio Paglia.
    Copyright (C) 2018-2022 Pascal Obry.
    Copyright (C) 2018 rawfiner.
    Copyright (C) 2019 Andreas Schneider.
    Copyright (C) 2019 Diederik ter Rahe.
    Copyright (C) 2020 Aldric Renaudin.
    Copyright (C) 2020 Chris Elston.
    Copyright (C) 2020 Diederik Ter Rahe.
    Copyright (C) 2020-2021 Hubert Kowalski.
    Copyright (C) 2020-2021 Ralf Brown.
    Copyright (C) 2022 Martin Bařinka.
    Copyright (C) 2022 Philipp Lutz.
    
    darktable 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.
    
    darktable 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 darktable.  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/gaussian.h"
#include "common/imagebuf.h"
#include "common/math.h"
#include "develop/develop.h"
#include "develop/imageop.h"
#include "develop/imageop_math.h"
#include "develop/imageop_gui.h"
#include "gui/gtk.h"
 
#include "iop/iop_api.h"
#include <gtk/gtk.h>
#include <stdlib.h>
 
DT_MODULE_INTROSPECTION(1, dt_iop_defringe_params_t)
 
typedef enum dt_iop_defringe_mode_t
{
  MODE_GLOBAL_AVERAGE = 0, // $DESCRIPTION: "global average (fast)"
  MODE_LOCAL_AVERAGE = 1,  // $DESCRIPTION: "local average (slow)"
  MODE_STATIC = 2          // $DESCRIPTION: "static threshold (fast)"
} dt_iop_defringe_mode_t;
 
typedef struct dt_iop_defringe_params_t
{
  float radius; // $MIN: 0.5 $MAX: 20.0 $DEFAULT: 4.0 $DESCRIPTION: "edge detection radius"
  float thresh; // $MIN: 0.5 $MAX: 128.0 $DEFAULT: 20.0 $DESCRIPTION: "threshold"
  dt_iop_defringe_mode_t op_mode; // $DEFAULT: MODE_GLOBAL_AVERAGE $DESCRIPTION: "operation mode"
} dt_iop_defringe_params_t;
 
typedef dt_iop_defringe_params_t dt_iop_defringe_data_t;
 
typedef struct dt_iop_defringe_gui_data_t
{
  GtkWidget *mode_select;
  GtkWidget *radius_scale;
  GtkWidget *thresh_scale;
} dt_iop_defringe_gui_data_t;
 
// would be nice to be able to precompute this only once for an image
// typedef struct dt_iop_defringe_global_data_t
//{
//  float avg_edge_chroma;
//}
// dt_iop_defringe_global_data_t;
 
 
const char *name()
{
  return _("defringe");
}
 
const char *aliases()
{
  return _("chromatic aberrations");
}
 
const char **description(struct dt_iop_module_t *self)
{
  return dt_iop_set_description(self, _("attenuate chromatic aberration by desaturating edges"),
                                      _("corrective"),
                                      _("linear or non-linear, Lab, display-referred"),
                                      _("non-linear, Lab"),
                                      _("non-linear, Lab, display-referred"));
}
 
int default_group()
{
  return IOP_GROUP_REPAIR;
}
 
int flags()
{
  // a second instance might help to reduce artifacts when thick fringe needs to be removed
  return IOP_FLAGS_SUPPORTS_BLENDING | IOP_FLAGS_DEPRECATED;
}
 
const char *deprecated_msg()
{
  return _("this module is deprecated. please use the chromatic aberration module instead.");
}
 
int default_colorspace(dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, const dt_dev_pixelpipe_iop_t *piece)
{
  return IOP_CS_LAB;
}
 
// Verify before actually using this
/*
void tiling_callback  (dt_iop_module_t *module, dt_dev_pixelpipe_iop_t *piece, const dt_iop_roi_t *roi_in,
const dt_iop_roi_t *roi_out, dt_develop_tiling_t *tiling)
{
  dt_iop_defringe_data_t *p = (dt_iop_defringe_data_t *)piece->data;
 
  const int width = roi_in->width;
  const int height = roi_in->height;
  const int channels = piece->dsc_in.channels;
  const size_t basebuffer = width*height*channels*sizeof(float);
 
  tiling->factor = 2.0f + (float)dt_gaussian_memory_use(width, height, channels)/basebuffer;
#ifdef HAVE_OPENCL
  tiling->factor_cl = 2.0f + (float)dt_gaussian_memory_use_cl(width, height, channels)/basebuffer;
#endif
  tiling->maxbuf = fmax(1.0f, (float)dt_gaussian_singlebuffer_size(width, height, channels)/basebuffer);
  tiling->overhead = 0;
  tiling->overlap = p->window;
  tiling->xalign = 1;
  tiling->yalign = 1;
  return;
}
*/
 
// fibonacci lattice to select surrounding pixels for different cases
static const float fib[] = { 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233 };
// 0,1,2,3,4,5,6, 7, 8, 9,10,11, 12, 13
 
static inline void fib_latt(int *const x, int *const y, float radius, int step, int idx)
{
  // idx < 1 because division by zero is also a problem in the following line
  if(idx >= sizeof(fib) / sizeof(float) - 1 || idx < 1)
  {
    *x = 0;
    *y = 0;
    fprintf(stderr, "Fibonacci lattice index wrong/out of bounds in: defringe module\n");
    return;
  }
  float px = step / fib[idx], py = step * (fib[idx + 1] / fib[idx]);
  py -= (int)py;
  float dx = px * radius, dy = py * radius;
  *x = round(dx - radius / 2.0);
  *y = round(dy - radius / 2.0);
}
 
#define MAGIC_THRESHOLD_COEFF 33.0
 
// the basis of how the following algorithm works comes from rawtherapee (http://rawtherapee.com/)
// defringe -- thanks to Emil Martinec <ejmartin@uchicago.edu> for that
// quite some modifications were done though:
// 1. use a fibonacci lattice instead of full window, to speed things up
// 2. option for local averaging or static (RT used the global/region one)
// 3. additional condition to reduce sharp edged artifacts, by blurring pixels near pixels over threshold,
// this really helps improving the filter with thick fringes
// -----------------------------------------------------------------------------------------
// in the following you will also see some more "magic numbers",
// most are chosen arbitrarily and/or by experiment/trial+error ... I am sorry ;-)
// and having everything user-defineable would be just too much
// -----------------------------------------------------------------------------------------
 
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_defringe_data_t));
  piece->data_size = sizeof(dt_iop_defringe_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;
}
 
__DT_CLONE_TARGETS__
int process(struct dt_iop_module_t *module, const dt_dev_pixelpipe_t *pipe, const dt_dev_pixelpipe_iop_t *piece,
            const void *const i,
             void *const o)
{
  (void)pipe;
  const dt_iop_roi_t *const roi_in = &piece->roi_in;
  const dt_iop_roi_t *const roi_out = &piece->roi_out;
  dt_iop_defringe_data_t *const d = (dt_iop_defringe_data_t *)piece->data;
 
  const int order = 1; // 0,1,2
  int err = 0;
  const float sigma = fmax(0.1f, fabs(d->radius)) * roi_in->scale;
  const float Labmax[] = { 100.0f, 128.0f, 128.0f, 1.0f };
  const float Labmin[] = { 0.0f, -128.0f, -128.0f, 0.0f };
  const int ch = 4;
  const int radius = ceil(2.0 * ceilf(sigma));
 
  // save the fibonacci lattices in them later
  int *xy_avg = NULL;
  int *xy_small = NULL;
 
  if(roi_out->width < 2 * radius + 1 || roi_out->height < 2 * radius + 1) goto ERROR_EXIT;
 
  float avg_edge_chroma = 0.0;
 
  const float *const restrict in = (float *const)i;
  float *const restrict out = (float *const)o;
  const int width = roi_in->width;
  const int height = roi_in->height;
 
  dt_gaussian_t *gauss = NULL;
  gauss = dt_gaussian_init(width, height, 4, Labmax, Labmin, sigma, order);
  if(IS_NULL_PTR(gauss))
  {
    fprintf(stderr, "Error allocating memory for gaussian blur in: defringe module\n");
    err = 1;
    goto ERROR_EXIT;
  }
  dt_gaussian_blur_4c(gauss, in, out);
  dt_gaussian_free(gauss);
 
  const int samples_wish = radius * radius;
  int sampleidx_avg;
  // select samples by fibonacci number
  if(samples_wish > 89)
  {
    sampleidx_avg = 12; // 144 samples
  }
  else if(samples_wish > 55)
  {
    sampleidx_avg = 11; // 89 samples
  }
  else if(samples_wish > 34)
  {
    sampleidx_avg = 10; // ..you get the idea
  }
  else if(samples_wish > 21)
  {
    sampleidx_avg = 9;
  }
  else if(samples_wish > 13)
  {
    sampleidx_avg = 8;
  }
  else
  { // don't use less than 13 samples
    sampleidx_avg = 7;
  }
  const int sampleidx_small = sampleidx_avg - 1;
 
  const int small_radius = MAX(radius, 3);
  const int avg_radius = 24 + radius * 4;
 
  const int samples_small = fib[sampleidx_small];
  const int samples_avg = fib[sampleidx_avg];
 
  // Pre-Compute Fibonacci Lattices
 
  xy_avg = malloc(sizeof(int) * 2 * samples_avg);
  xy_small = malloc(sizeof(int) * 2 * samples_small);
  if(IS_NULL_PTR(xy_avg) || IS_NULL_PTR(xy_small))
  {
    fprintf(stderr, "Error allocating memory for fibonacci lattice in: defringe module\n");
    err = 1;
    goto ERROR_EXIT;
  }
 
  // precompute all required fibonacci lattices:
  for(int u = 0; u < samples_avg; u++)
  {
    int dx, dy;
    fib_latt(&dx, &dy, avg_radius, u, sampleidx_avg);
    xy_avg[2*u] = dx;
    xy_avg[2*u+1] = dy;
  }
  for(int u = 0; u < samples_small; u++)
  {
    int dx, dy;
    fib_latt(&dx, &dy, small_radius, u, sampleidx_small);
    xy_small[2*u] = dx;
    xy_small[2*u+1] = dy;
  }
 
  const float use_global_average = MODE_GLOBAL_AVERAGE == d->op_mode;
  __OMP_PARALLEL_FOR_SIMD__(reduction(+ : avg_edge_chroma))
  for(size_t j = 0; j < (size_t)height * width * 4; j += 4)
  {
    // edge-detect on color channels
    // method: difference of original to gaussian blurred image:
    const float a = in[j + 1] - out[j + 1];
    const float b = in[j + 2] - out[j + 2];
    const float edge = (a * a + b * b); // range up to 2*(256)^2 -> approx. 0 to 131072
 
    // save local edge chroma in out[.. +3] , this is later compared with threshold
    out[j + 3] = edge;
    // the average chroma of the edge-layer in the roi
    avg_edge_chroma += edge * use_global_average;
  }
 
  float thresh;
  if(use_global_average)
  {
    avg_edge_chroma = avg_edge_chroma / (width * height) + 10.0 * FLT_EPSILON;
    thresh = fmax(0.1f, 4.0 * d->thresh * avg_edge_chroma / MAGIC_THRESHOLD_COEFF);
  }
  else
  {
    // this fixed value will later be changed when doing local averaging, or kept as-is in "static" mode
    avg_edge_chroma = MAGIC_THRESHOLD_COEFF;
    thresh = fmax(0.1f, d->thresh);
  }
 
#ifdef _OPENMP
// dynamically/guided scheduled due to possible uneven edge-chroma distribution (thanks to rawtherapee code
// for this hint!)
#pragma omp parallel for default(firstprivate) \
  schedule(dynamic,3)
#endif
  for(int v = 0; v < height; v++)
  {
    const size_t row_above = (size_t)MAX(0, (v-1)) * width * ch;
    const size_t curr_row = (size_t)v * width * ch;
    const size_t row_below = (size_t)MIN((height-1), (v+1)) * width * ch;
    for(int t = 0; t < width; t++)
    {
      const size_t index = ch * ((size_t)v * width + t);
      float local_thresh = thresh;
      // think of compiler setting "-funswitch-loops" to maybe improve these things:
      if(MODE_LOCAL_AVERAGE == d->op_mode && out[index + 3] > thresh)
      {
        float local_avg = 0.0;
        // use some and not all values from the neighbourhood to speed things up:
        for(int u = 0; u < samples_avg; u++)
        {
          const int dx = xy_avg[2*u];
          const int dy = xy_avg[2*u+1];
          const int x = CLAMP(t + dx, 0, width - 1);
          const int y = CLAMP(v + dy, 0, height - 1);
          local_avg += out[((size_t)y * width + x) * ch + 3];
        }
        avg_edge_chroma = fmax(0.01f, (float)local_avg / samples_avg);
        local_thresh = fmax(0.1f, 4.0 * d->thresh * avg_edge_chroma / MAGIC_THRESHOLD_COEFF);
      }
 
      if(out[index + 3] > local_thresh
         // reduces artifacts ("region growing by 1 pixel"):
         || out[row_above + MAX(0, (t - 1)) * ch + 3] > local_thresh
         || out[row_above + t * ch + 3] > local_thresh
         || out[row_above + MIN(width - 1, (t + 1)) * ch + 3] > local_thresh
         || out[curr_row + MAX(0, (t - 1)) * ch + 3] > local_thresh
         || out[curr_row + MIN(width - 1, (t + 1)) * ch + 3] > local_thresh
         || out[row_below + MAX(0, (t - 1)) * ch + 3] > local_thresh
         || out[row_below + t * ch + 3] > local_thresh
         || out[row_below + MIN(width - 1, (t + 1)) * ch + 3] > local_thresh)
      {
        float atot = 0, btot = 0;
        float norm = 0;
        float weight;
        // it seems better to use only some pixels from a larger window instead of all pixels from a smaller
        // window
        // we use a fibonacci lattice for that, samples amount need to be a fibonacci number, this can then be
        // scaled to
        // a certain radius
 
        // use some neighbourhood pixels for lowest chroma average
        for(int u = 0; u < samples_small; u++)
        {
          const int dx = xy_small[2*u];
          const int dy = xy_small[2*u+1];
          const int x = CLAMP(t + dx, 0, width - 1);
          const int y = CLAMP(v + dy, 0, height - 1);
          const size_t idx = ch * ((size_t)y * width + x);
          // inverse chroma weighted average of neighbouring pixels inside window
          // also taking average edge chromaticity into account (either global or local average)
          weight = 1.0 / (out[idx + 3] + avg_edge_chroma);
          atot += weight * in[idx + 1];
          btot += weight * in[idx + 2];
          norm += weight;
        }
        // here we could try using a "balance" between original and changed value, this could be used to
        // reduce artifacts
        // but on first tries, results weren't very convincing, and there are blend settings available anyway
        // in dt
        // float balance = (out[v*width*ch +t*ch +3]-thresh)/out[v*width*ch +t*ch +3];
        double a = (atot / norm); // *balance + in[v*width*ch + t*ch +1]*(1.0-balance);
        double b = (btot / norm); // *balance + in[v*width*ch + t*ch +2]*(1.0-balance);
        out[index] = in[index];
        out[index + 1] = a;
        out[index + 2] = b;
      }
      else
      {
        __OMP_SIMD__(aligned(in, out))
        // we can't copy the alpha channel here because it contains info needed by neighboring pixels!
        for(int c = 0; c < 3; c++)
        {
          out[index+c] = in[index+c];
        }
      }
    }
  }
 
  if(pipe->mask_display & DT_DEV_PIXELPIPE_DISPLAY_MASK)
    dt_iop_alpha_copy(i, o, roi_out->width, roi_out->height);
 
  goto FINISH_PROCESS;
 
ERROR_EXIT:
  dt_iop_image_copy_by_size(o, i, roi_out->width, roi_out->height, ch);
 
FINISH_PROCESS:
  dt_free(xy_small);
  dt_free(xy_avg);
  return err;
}
 
void gui_init(dt_iop_module_t *self)
{
  dt_iop_defringe_gui_data_t *g = IOP_GUI_ALLOC(defringe);
 
  g->mode_select = dt_bauhaus_combobox_from_params(self, "op_mode");
  gtk_widget_set_tooltip_text(g->mode_select,
      _("method for color protection:\n - global average: fast, might show slightly wrong previews in high "
        "magnification; might sometimes protect saturation too much or too low in comparison to local "
        "average\n - local average: slower, might protect saturation better than global average by using "
        "near pixels as color reference, so it can still allow for more desaturation where required\n - "
        "static: fast, only uses the threshold as a static limit"));
 
  g->radius_scale = dt_bauhaus_slider_from_params(self, "radius");
  gtk_widget_set_tooltip_text(g->radius_scale, _("radius for detecting fringe"));
 
  g->thresh_scale = dt_bauhaus_slider_from_params(self, "thresh");
  gtk_widget_set_tooltip_text(g->thresh_scale, _("threshold for defringe, higher values mean less defringing"));
}
 
void gui_update(dt_iop_module_t *module)
{
  dt_iop_defringe_gui_data_t *g = (dt_iop_defringe_gui_data_t *)module->gui_data;
  dt_iop_defringe_params_t *p = (dt_iop_defringe_params_t *)module->params;
  dt_bauhaus_combobox_set(g->mode_select, p->op_mode);
  dt_bauhaus_slider_set(g->radius_scale, p->radius);
  dt_bauhaus_slider_set(g->thresh_scale, p->thresh);
}
 
// 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