luminance_mask.h

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/*
    This file is part of darktable,
    Copyright (C) 2019 Aurélien PIERRE.
    Copyright (C) 2019 luzpaz.
    Copyright (C) 2019-2020 Pascal Obry.
    Copyright (C) 2020 Diederik Ter Rahe.
    Copyright (C) 2022 Martin Bařinka.
    Copyright (C) 2022 Sakari Kapanen.
    
    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/>.
*/
 
#ifndef DT_PIXEL_LUMINANCE_MASK_H
#define DT_PIXEL_LUMINANCE_MASK_H
#include <assert.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
 
#include "system/openmp.h"
#include "system/target_clones.h"
 
 
#define MIN_FLOAT exp2f(-16.0f)
 
 
typedef enum dt_iop_luminance_mask_method_t
{
  DT_TONEEQ_MEAN = 0,   // $DESCRIPTION: "RGB average"
  DT_TONEEQ_LIGHTNESS,  // $DESCRIPTION: "HSL lightness"
  DT_TONEEQ_VALUE,      // $DESCRIPTION: "HSV value / RGB max"
  DT_TONEEQ_NORM_1,     // $DESCRIPTION: "RGB sum"
  DT_TONEEQ_NORM_2,     // $DESCRIPTION: "RGB euclidean norm")
  DT_TONEEQ_NORM_POWER, // $DESCRIPTION: "RGB power norm"
  DT_TONEEQ_GEOMEAN,    // $DESCRIPTION: "RGB geometric mean"
  DT_TONEEQ_LAST
} dt_iop_luminance_mask_method_t;
 
__OMP_DECLARE_SIMD__()
static float linear_contrast(const float pixel, const float fulcrum, const float contrast)
{
  // Increase the slope of the value around a fulcrum value
  return fmaxf((pixel - fulcrum) * contrast + fulcrum, MIN_FLOAT);
}
 
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_mean(const float *const restrict image,
                           float *const restrict luminance,
                           const size_t k, const size_t ch,
                           const float exposure_boost,
                           const float fulcrum, const float contrast_boost)
{
  // mean(RGB) is the intensity
 
  float lum = 0.0f;
  __OMP_SIMD__(reduction(+:lum) aligned(image:64))
  for(int c = 0; c < 3; ++c)
    lum += image[k + c];
 
  luminance[k / ch] = linear_contrast(exposure_boost * lum / 3.0f, fulcrum, contrast_boost);
}
 
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_value(const float *const restrict image,
                            float *const restrict luminance,
                            const size_t k, const size_t ch,
                            const float exposure_boost,
                            const float fulcrum, const float contrast_boost)
{
  // max(RGB) is equivalent to HSV value
 
  const float lum = exposure_boost * fmaxf(fmaxf(image[k], image[k + 1]), image[k + 2]);
  luminance[k / ch] = linear_contrast(lum, fulcrum, contrast_boost);
}
 
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_lightness(const float *const restrict image,
                                float *const restrict luminance,
                                const size_t k, const size_t ch,
                                const float exposure_boost,
                                const float fulcrum, const float contrast_boost)
{
  // (max(RGB) + min(RGB)) / 2 is equivalent to HSL lightness
 
  const float max_rgb = fmaxf(fmaxf(image[k], image[k + 1]), image[k + 2]);
  const float min_rgb = fminf(fminf(image[k], image[k + 1]), image[k + 2]);
  luminance[k / ch] = linear_contrast(exposure_boost * (max_rgb + min_rgb) / 2.0f, fulcrum, contrast_boost);
}
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_norm_1(const float *const restrict image,
                             float *const restrict luminance,
                             const size_t k, const size_t ch,
                             const float exposure_boost,
                             const float fulcrum, const float contrast_boost)
{
  // vector norm L1
 
  float lum = 0.0f;
    __OMP_SIMD__(reduction(+:lum) aligned(image:64))
    for(int c = 0; c < 3; ++c)
      lum += fabsf(image[k + c]);
 
  luminance[k / ch] = linear_contrast(exposure_boost * lum, fulcrum, contrast_boost);
}
 
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_norm_2(const float *const restrict image,
                             float *const restrict luminance,
                             const size_t k, const size_t ch,
                             const float exposure_boost,
                             const float fulcrum, const float contrast_boost)
{
  // vector norm L2 : euclidean norm
 
  float result = 0.0f;
  __OMP_SIMD__(aligned(image:64) reduction(+: result))
  for(int c = 0; c < 3; ++c) result += image[k + c] * image[k + c];
 
  luminance[k / ch] = linear_contrast(exposure_boost * sqrtf(result), fulcrum, contrast_boost);
}
 
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_norm_power(const float *const restrict image,
                                 float *const restrict luminance,
                                 const size_t k, const size_t ch,
                                 const float exposure_boost,
                                 const float fulcrum, const float contrast_boost)
{
  // weird norm sort of perceptual. This is black magic really, but it looks good.
 
  float numerator = 0.0f;
  float denominator = 0.0f;
  __OMP_SIMD__(aligned(image:64) reduction(+:numerator, denominator))
  for(int c = 0; c < 3; ++c)
  {
    const float value = fabsf(image[k + c]);
    const float RGB_square = value * value;
    const float RGB_cubic = RGB_square * value;
    numerator += RGB_cubic;
    denominator += RGB_square;
  }
 
  luminance[k / ch] = linear_contrast(exposure_boost * numerator / denominator, fulcrum, contrast_boost);
}
 
__OMP_DECLARE_SIMD__(aligned(image, luminance:64) uniform(image, luminance))
static void pixel_rgb_geomean(const float *const restrict image,
                              float *const restrict luminance,
                              const size_t k, const size_t ch,
                              const float exposure_boost,
                              const float fulcrum, const float contrast_boost)
{
  // geometric_mean(RGB). Kind of interesting for saturated colours (maps them to shadows)
 
  float lum = 1.0f;
  __OMP_SIMD__(aligned(image:64) reduction(*:lum))
  for(int c = 0; c < 3; ++c)
  {
    lum *= fabsf(image[k + c]);
  }
 
  luminance[k / ch] = linear_contrast(exposure_boost * powf(lum, 1.0f / 3.0f), fulcrum, contrast_boost);
}
 
 
// Overkill trick to explicitely unswitch loops
// GCC should to it automatically with "funswitch-loops" flag,
// but not sure about Clang
#ifdef _OPENMP
  #define LOOP(fn)                                                        \
    {                                                                     \
      _Pragma ("omp parallel for simd default(firstprivate) \
      aligned(in, out:64)" )                                              \
      for(size_t k = 0; k < num_elem; k += ch)                            \
      {                                                                   \
        fn(in, out, k, ch, exposure_boost, fulcrum, contrast_boost);      \
      }                                                                   \
      break;                                                              \
    }
#else
  #define LOOP(fn)                                                        \
    {                                                                     \
      for(size_t k = 0; k < num_elem; k += ch)                            \
      {                                                                   \
        fn(in, out, k, ch, exposure_boost, fulcrum, contrast_boost);      \
      }                                                                   \
      break;                                                              \
    }
#endif
 
 
__DT_CLONE_TARGETS__
static inline void luminance_mask(const float *const restrict in, float *const restrict out,
                           const size_t width, const size_t height, const size_t ch,
                           const dt_iop_luminance_mask_method_t method,
                           const float exposure_boost,
                           const float fulcrum, const float contrast_boost)
{
  const size_t num_elem = width * height * ch;
  switch(method)
  {
    case DT_TONEEQ_MEAN:
      LOOP(pixel_rgb_mean);
 
    case DT_TONEEQ_LIGHTNESS:
      LOOP(pixel_rgb_lightness);
 
    case DT_TONEEQ_VALUE:
      LOOP(pixel_rgb_value);
 
    case DT_TONEEQ_NORM_1:
      LOOP(pixel_rgb_norm_1);
 
    case DT_TONEEQ_NORM_2:
      LOOP(pixel_rgb_norm_2);
 
    case DT_TONEEQ_NORM_POWER:
      LOOP(pixel_rgb_norm_power);
 
    case DT_TONEEQ_GEOMEAN:
      LOOP(pixel_rgb_geomean);
 
    default:
      break;
  }
}
 
#endif // DT_PIXEL_LUMINANCE_MASK_H
 
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