lch.c

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/*
   This file is part of darktable,
   Copyright (C) 2010 Bruce Guenter.
   Copyright (C) 2010-2011 Henrik Andersson.
   Copyright (C) 2010-2014, 2016 johannes hanika.
   Copyright (C) 2010 Stuart Henderson.
   Copyright (C) 2011 Antony Dovgal.
   Copyright (C) 2011 Robert Bieber.
   Copyright (C) 2011-2014, 2016, 2019 Tobias Ellinghaus.
   Copyright (C) 2011-2012, 2014, 2016-2017 Ulrich Pegelow.
   Copyright (C) 2012, 2015 Edouard Gomez.
   Copyright (C) 2012 Jérémy Rosen.
   Copyright (C) 2012 Richard Wonka.
   Copyright (C) 2013, 2020 Aldric Renaudin.
   Copyright (C) 2014, 2016 Dan Torop.
   Copyright (C) 2014-2016 Roman Lebedev.
   Copyright (C) 2015-2016 Pedro Côrte-Real.
   Copyright (C) 2017 Heiko Bauke.
   Copyright (C) 2017 luzpaz.
   Copyright (C) 2018, 2020-2026 Aurélien PIERRE.
   Copyright (C) 2018 Edgardo Hoszowski.
   Copyright (C) 2018 Maurizio Paglia.
   Copyright (C) 2018-2020, 2022 Pascal Obry.
   Copyright (C) 2018 rawfiner.
   Copyright (C) 2019 Andreas Schneider.
   Copyright (C) 2019 Diederik ter Rahe.
   Copyright (C) 2019-2020, 2022 Hanno Schwalm.
   Copyright (C) 2020 Chris Elston.
   Copyright (C) 2020, 2022 Diederik Ter Rahe.
   Copyright (C) 2020-2021 Ralf Brown.
   Copyright (C) 2021 Hubert Kowalski.
   Copyright (C) 2022 Martin Bařinka.
   Copyright (C) 2022 Philipp Lutz.
   Copyright (C) 2022 Victor Forsiuk.
   Copyright (C) 2023 Alynx Zhou.
   Copyright (C) 2023 Guillaume Stutin.
   Copyright (C) 2023 Luca Zulberti.
 
   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/>.
 */
 
// LCh highlight reconstruction (Bayer + X-Trans), with its colour interpolation helpers. (implementation; see
// lch.h for the public API.)
 
#include "common/darktable.h"
#include "develop/imageop_math.h"
#include "iop/highlights/lch.h"
#include <math.h>
#include <string.h>
 
/* interpolate value for a pixel, ideal via ratio to nearby pixel */
static inline float interp_pix_xtrans(const int ratio_next, const ssize_t offset_next, const float clip0,
                                      const float clip_next, const float *const in, const float *const ratios)
{
  assert(ratio_next != 0);
  // it's OK to exceed clipping of current pixel's color based on a
  // neighbor -- that is the purpose of interpolating highlight
  // colors
  const float clip_val = fmaxf(clip0, clip_next);
  if(in[offset_next] >= clip_next - 1e-5f)
  {
    // next pixel is also clipped
    return clip_val;
  }
  else
  {
    // set this pixel in ratio to the next
    assert(ratio_next != 0);
    if(ratio_next > 0)
      return fminf(in[offset_next] / ratios[ratio_next], clip_val);
    else
      return fminf(in[offset_next] * ratios[-ratio_next], clip_val);
  }
}
 
void interpolate_color_xtrans(const void *const ivoid, void *const ovoid, const dt_iop_roi_t *const roi_in,
                              const dt_iop_roi_t *const roi_out, int dim, int dir, int other,
                              const float *const clip, const uint8_t (*const xtrans)[6], const int pass)
{
  // In Bayer each row/col has only green/red or green/blue
  // transitions, hence can reconstruct color by single ratio per
  // row. In x-trans there can be transitions between arbitrary colors
  // in a row/col (and 2x2 green blocks which provide no color
  // transition information). Hence calculate multiple color ratios
  // for each row/col.
 
  // Lookup for color ratios, e.g. red -> blue is roff[0][2] and blue
  // -> red is roff[2][0]. Returned value is an index into ratios. If
  // negative, then need to invert the ratio. Identity color
  // transitions aren't used.
  const int roff[3][3] = { { 0, -1, -2 }, { 1, 0, -3 }, { 2, 3, 0 } };
  // record ratios of color transitions 0:unused, 1:RG, 2:RB, and 3:GB
  dt_aligned_pixel_t ratios = { 1.0f, 1.0f, 1.0f, 1.0f };
 
  // passes are 0:+x, 1:-x, 2:+y, 3:-y
  // dims are 0:traverse a row, 1:traverse a column
  // dir is 1:left to right, -1: right to left
  int i = (dim == 0) ? 0 : other;
  int j = (dim == 0) ? other : 0;
  const ssize_t offs = (ssize_t)(dim ? roi_out->width : 1) * ((dir < 0) ? -1 : 1);
  const ssize_t offl = offs - (dim ? 1 : roi_out->width);
  const ssize_t offr = offs + (dim ? 1 : roi_out->width);
  int beg, end;
  if(dir == 1)
  {
    beg = 0;
    end = (dim == 0) ? roi_out->width : roi_out->height;
  }
  else
  {
    beg = ((dim == 0) ? roi_out->width : roi_out->height) - 1;
    end = -1;
  }
 
  float *in, *out;
  if(dim == 1)
  {
    out = (float *)ovoid + (size_t)i + (size_t)beg * roi_out->width;
    in = (float *)ivoid + (size_t)i + (size_t)beg * roi_in->width;
  }
  else
  {
    out = (float *)ovoid + (size_t)beg + (size_t)j * roi_out->width;
    in = (float *)ivoid + (size_t)beg + (size_t)j * roi_in->width;
  }
 
  for(int k = beg; k != end; k += dir)
  {
    if(dim == 1)
      j = k;
    else
      i = k;
 
    const uint8_t f0 = FCxtrans(j, i, roi_in, xtrans);
    const uint8_t f1 = FCxtrans(dim ? (j + dir) : j, dim ? i : (i + dir), roi_in, xtrans);
    const uint8_t fl = FCxtrans(dim ? (j + dir) : (j - 1), dim ? (i - 1) : (i + dir), roi_in, xtrans);
    const uint8_t fr = FCxtrans(dim ? (j + dir) : (j + 1), dim ? (i + 1) : (i + dir), roi_in, xtrans);
    const float clip0 = clip[f0];
    const float clip1 = clip[f1];
    const float clipl = clip[fl];
    const float clipr = clip[fr];
    const float clip_max = fmaxf(fmaxf(clip[0], clip[1]), clip[2]);
 
    if(i == 0 || i == roi_out->width - 1 || j == 0 || j == roi_out->height - 1)
    {
      if(pass == 3) out[0] = fminf(clip_max, in[0]);
    }
    else
    {
      // ratio to next pixel if this & next are unclamped and not in
      // 2x2 green block
      if((f0 != f1) && (in[0] < clip0 && in[0] > 1e-5f) && (in[offs] < clip1 && in[offs] > 1e-5f))
      {
        const int r = roff[f0][f1];
        assert(r != 0);
        if(r > 0)
          ratios[r] = (3.f * ratios[r] + (in[offs] / in[0])) / 4.f;
        else
          ratios[-r] = (3.f * ratios[-r] + (in[0] / in[offs])) / 4.f;
      }
 
      if(in[0] >= clip0 - 1e-5f)
      {
        // interplate color for clipped pixel
        float add;
        if(f0 != f1)
          // next pixel is different color
          add = interp_pix_xtrans(roff[f0][f1], offs, clip0, clip1, in, ratios);
        else
          // at start of 2x2 green block, look diagonally
          add = (fl != f0) ? interp_pix_xtrans(roff[f0][fl], offl, clip0, clipl, in, ratios)
                           : interp_pix_xtrans(roff[f0][fr], offr, clip0, clipr, in, ratios);
 
        if(pass == 0)
          out[0] = add;
        else if(pass == 3)
          out[0] = fminf(clip_max, (out[0] + add) / 4.0f);
        else
          out[0] += add;
      }
      else
      {
        // pixel is not clipped
        if(pass == 3) out[0] = in[0];
      }
    }
    out += offs;
    in += offs;
  }
}
 
void interpolate_color(const void *const ivoid, void *const ovoid, const dt_iop_roi_t *const roi_out, int dim,
                       int dir, int other, const float *clip, const uint32_t filters, const int pass)
{
  float ratio = 1.0f;
  float *in, *out;
 
  int i = 0, j = 0;
  if(dim == 0)
    j = other;
  else
    i = other;
  ssize_t offs = dim ? roi_out->width : 1;
  if(dir < 0) offs = -offs;
  int beg, end;
  if(dim == 0 && dir == 1)
  {
    beg = 0;
    end = roi_out->width;
  }
  else if(dim == 0 && dir == -1)
  {
    beg = roi_out->width - 1;
    end = -1;
  }
  else if(dim == 1 && dir == 1)
  {
    beg = 0;
    end = roi_out->height;
  }
  else if(dim == 1 && dir == -1)
  {
    beg = roi_out->height - 1;
    end = -1;
  }
  else
    return;
 
  if(dim == 1)
  {
    out = (float *)ovoid + i + (size_t)beg * roi_out->width;
    in = (float *)ivoid + i + (size_t)beg * roi_out->width;
  }
  else
  {
    out = (float *)ovoid + beg + (size_t)j * roi_out->width;
    in = (float *)ivoid + beg + (size_t)j * roi_out->width;
  }
  for(int k = beg; k != end; k += dir)
  {
    if(dim == 1)
      j = k;
    else
      i = k;
    const float clip0 = clip[FC(j, i, filters)];
    const float clip1 = clip[FC(dim ? (j + 1) : j, dim ? i : (i + 1), filters)];
    if(i == 0 || i == roi_out->width - 1 || j == 0 || j == roi_out->height - 1)
    {
      if(pass == 3) out[0] = in[0];
    }
    else
    {
      if(in[0] < clip0 && in[0] > 1e-5f)
      { // both are not clipped
        if(in[offs] < clip1 && in[offs] > 1e-5f)
        { // update ratio, exponential decay. ratio = in[odd]/in[even]
          if(k & 1)
            ratio = (3.0f * ratio + in[0] / in[offs]) / 4.0f;
          else
            ratio = (3.0f * ratio + in[offs] / in[0]) / 4.0f;
        }
      }
 
      if(in[0] >= clip0 - 1e-5f)
      { // in[0] is clipped, restore it as in[1] adjusted according to ratio
        float add = 0.0f;
        if(in[offs] >= clip1 - 1e-5f)
          add = fmaxf(clip0, clip1);
        else if(k & 1)
          add = in[offs] * ratio;
        else
          add = in[offs] / ratio;
 
        if(pass == 0)
          out[0] = add;
        else if(pass == 3)
          out[0] = (out[0] + add) / 4.0f;
        else
          out[0] += add;
      }
      else
      {
        if(pass == 3) out[0] = in[0];
      }
    }
    out += offs;
    in += offs;
  }
}
 
/*
 * these 2 constants were computed using following Sage code:
 *
 * sqrt3 = sqrt(3)
 * sqrt12 = sqrt(12) # 2*sqrt(3)
 *
 * print 'sqrt3 = ', sqrt3, ' ~= ', RealField(128)(sqrt3)
 * print 'sqrt12 = ', sqrt12, ' ~= ', RealField(128)(sqrt12)
 */
 
__DT_CLONE_TARGETS__
void process_lch_bayer(dt_iop_module_t *self, const dt_dev_pixelpipe_iop_t *piece, const void *const ivoid,
                       void *const ovoid, const dt_iop_roi_t *const roi_in, const dt_iop_roi_t *const roi_out,
                       const float clip)
{
  const uint32_t filters = piece->dsc_in.filters;
  __OMP_PARALLEL_FOR__(collapse(2))
  for(int j = 0; j < roi_out->height; j++)
  {
    for(int i = 0; i < roi_out->width; i++)
    {
      float *const out = (float *)ovoid + (size_t)roi_out->width * j + i;
      const float *const in = (float *)ivoid + (size_t)roi_out->width * j + i;
 
      if(i == roi_out->width - 1 || j == roi_out->height - 1)
      {
        // fast path for border
        out[0] = MIN(clip, in[0]);
      }
      else
      {
        int clipped = 0;
 
        // sample 1 bayer block. thus we will have 2 green values.
        float R = 0.0f, Gmin = FLT_MAX, Gmax = -FLT_MAX, B = 0.0f;
        for(int jj = 0; jj <= 1; jj++)
        {
          for(int ii = 0; ii <= 1; ii++)
          {
            const float val = in[(size_t)jj * roi_out->width + ii];
 
            clipped = (clipped || (val > clip));
 
            const int c = FC(j + jj + roi_out->y, i + ii + roi_out->x, filters);
            switch(c)
            {
              case 0:
                R = val;
                break;
              case 1:
                Gmin = MIN(Gmin, val);
                Gmax = MAX(Gmax, val);
                break;
              case 2:
                B = val;
                break;
            }
          }
        }
 
        if(clipped)
        {
          const float Ro = MIN(R, clip);
          const float Go = MIN(Gmin, clip);
          const float Bo = MIN(B, clip);
 
          const float L = (R + Gmax + B) / 3.0f;
 
          float C = SQRT3 * (R - Gmax);
          float H = 2.0f * B - Gmax - R;
 
          const float Co = SQRT3 * (Ro - Go);
          const float Ho = 2.0f * Bo - Go - Ro;
 
          if(R != Gmax && Gmax != B)
          {
            const float ratio = sqrtf((Co * Co + Ho * Ho) / (C * C + H * H));
            C *= ratio;
            H *= ratio;
          }
 
          dt_aligned_pixel_t RGB = { 0.0f, 0.0f, 0.0f };
 
          /*
           * backtransform proof, sage:
           *
           * R,G,B,L,C,H = var('R,G,B,L,C,H')
           * solve([L==(R+G+B)/3, C==sqrt(3)*(R-G), H==2*B-G-R], R, G, B)
           *
           * result:
           * [[R == 1/6*sqrt(3)*C - 1/6*H + L, G == -1/6*sqrt(3)*C - 1/6*H + L, B == 1/3*H + L]]
           */
          RGB[0] = L - H / 6.0f + C / SQRT12;
          RGB[1] = L - H / 6.0f - C / SQRT12;
          RGB[2] = L + H / 3.0f;
 
          out[0] = RGB[FC(j + roi_out->y, i + roi_out->x, filters)];
        }
        else
        {
          out[0] = in[0];
        }
      }
    }
  }
}
 
__DT_CLONE_TARGETS__
void process_lch_xtrans(dt_iop_module_t *self, const dt_dev_pixelpipe_iop_t *piece, const void *const ivoid,
                        void *const ovoid, const dt_iop_roi_t *const roi_in, const dt_iop_roi_t *const roi_out,
                        const float clip)
{
  const uint8_t(*const xtrans)[6] = (const uint8_t(*const)[6])piece->dsc_in.xtrans;
  __OMP_PARALLEL_FOR__()
  for(int j = 0; j < roi_out->height; j++)
  {
    float *out = (float *)ovoid + (size_t)roi_out->width * j;
    float *in = (float *)ivoid + (size_t)roi_in->width * j;
 
    // bit vector used as ring buffer to remember clipping of current
    // and last two columns, checking current pixel and its vertical
    // neighbors
    int cl = 0;
 
    for(int i = 0; i < roi_out->width; i++)
    {
      // update clipping ring buffer
      cl = (cl << 1) & 6;
      if(j >= 2 && j <= roi_out->height - 3)
      {
        cl |= (in[-roi_in->width] > clip) | (in[0] > clip) | (in[roi_in->width] > clip);
      }
 
      if(i < 2 || i > roi_out->width - 3 || j < 2 || j > roi_out->height - 3)
      {
        // fast path for border
        out[0] = MIN(clip, in[0]);
      }
      else
      {
        // if current pixel is clipped, always reconstruct
        int clipped = (in[0] > clip);
        if(!clipped)
        {
          clipped = cl;
          if(clipped)
          {
            // If the ring buffer can't show we are in an obviously
            // unclipped region, this is the slow case: check if there
            // is any 3x3 block touching the current pixel which has
            // no clipping, as then don't need to reconstruct the
            // current pixel. This avoids zippering in edge
            // transitions from clipped to unclipped areas. The
            // X-Trans sensor seems prone to this, unlike Bayer, due
            // to its irregular pattern.
            for(int offset_j = -2; offset_j <= 0; offset_j++)
            {
              for(int offset_i = -2; offset_i <= 0; offset_i++)
              {
                if(clipped)
                {
                  clipped = 0;
                  for(int jj = offset_j; jj <= offset_j + 2; jj++)
                  {
                    for(int ii = offset_i; ii <= offset_i + 2; ii++)
                    {
                      const float val = in[(ssize_t)jj * roi_in->width + ii];
                      clipped = (clipped || (val > clip));
                    }
                  }
                }
              }
            }
          }
        }
 
        if(clipped)
        {
          dt_aligned_pixel_t mean = { 0.0f, 0.0f, 0.0f };
          dt_aligned_pixel_t RGBmax = { -FLT_MAX, -FLT_MAX, -FLT_MAX };
          int cnt[3] = { 0, 0, 0 };
 
          for(int jj = -1; jj <= 1; jj++)
          {
            for(int ii = -1; ii <= 1; ii++)
            {
              const float val = in[(ssize_t)jj * roi_in->width + ii];
              const int c = FCxtrans(j + jj, i + ii, roi_in, xtrans);
              mean[c] += val;
              cnt[c]++;
              RGBmax[c] = MAX(RGBmax[c], val);
            }
          }
 
          const float Ro = MIN(mean[0] / cnt[0], clip);
          const float Go = MIN(mean[1] / cnt[1], clip);
          const float Bo = MIN(mean[2] / cnt[2], clip);
 
          const float R = RGBmax[0];
          const float G = RGBmax[1];
          const float B = RGBmax[2];
 
          const float L = (R + G + B) / 3.0f;
 
          float C = SQRT3 * (R - G);
          float H = 2.0f * B - G - R;
 
          const float Co = SQRT3 * (Ro - Go);
          const float Ho = 2.0f * Bo - Go - Ro;
 
          if(R != G && G != B)
          {
            const float ratio = sqrtf((Co * Co + Ho * Ho) / (C * C + H * H));
            C *= ratio;
            H *= ratio;
          }
 
          dt_aligned_pixel_t RGB = { 0.0f, 0.0f, 0.0f };
 
          RGB[0] = L - H / 6.0f + C / SQRT12;
          RGB[1] = L - H / 6.0f - C / SQRT12;
          RGB[2] = L + H / 3.0f;
 
          out[0] = RGB[FCxtrans(j, i, roi_out, xtrans)];
        }
        else
          out[0] = in[0];
      }
      out++;
      in++;
    }
  }
}