gstreamer/gst/dvbsubenc/libimagequant/viter.c

#include "libimagequant.h"
#include "pam.h"
#include "viter.h"
#include "nearest.h"
#include <stdlib.h>
#include <string.h>

#ifdef _OPENMP
#include <omp.h>
#else
#define omp_get_max_threads() 1
#define omp_get_thread_num() 0
#endif

/*
 * Voronoi iteration: new palette color is computed from weighted average of colors that map to that palette entry.
 */
LIQ_PRIVATE void
viter_init (const colormap * map, const unsigned int max_threads,
    viter_state average_color[])
{
  memset (average_color, 0,
      sizeof (average_color[0]) * (VITER_CACHE_LINE_GAP +
          map->colors) * max_threads);
}

LIQ_PRIVATE void
viter_update_color (const f_pixel acolor, const float value,
    const colormap * map, unsigned int match, const unsigned int thread,
    viter_state average_color[])
{
  match += thread * (VITER_CACHE_LINE_GAP + map->colors);
  average_color[match].a += acolor.a * value;
  average_color[match].r += acolor.r * value;
  average_color[match].g += acolor.g * value;
  average_color[match].b += acolor.b * value;
  average_color[match].total += value;
}

LIQ_PRIVATE void
viter_finalize (colormap * map, const unsigned int max_threads,
    const viter_state average_color[])
{
  for (unsigned int i = 0; i < map->colors; i++) {
    double a = 0, r = 0, g = 0, b = 0, total = 0;

    // Aggregate results from all threads
    for (unsigned int t = 0; t < max_threads; t++) {
      const unsigned int offset = (VITER_CACHE_LINE_GAP + map->colors) * t + i;

      a += average_color[offset].a;
      r += average_color[offset].r;
      g += average_color[offset].g;
      b += average_color[offset].b;
      total += average_color[offset].total;
    }

    if (total && !map->palette[i].fixed) {
      map->palette[i].acolor = (f_pixel) {
      .a = a / total,.r = r / total,.g = g / total,.b = b / total,};
    } else {
      total = i / 1024.0;
    }
    map->palette[i].popularity = total;
  }
}

LIQ_PRIVATE double
viter_do_iteration (histogram * hist, colormap * const map,
    const float min_opaque_val, viter_callback callback,
    const bool fast_palette)
{
  viter_state *average_color;
  const unsigned int max_threads = omp_get_max_threads ();
  double total_diff = 0;

  average_color =
      g_alloca (sizeof (viter_state) * (VITER_CACHE_LINE_GAP +
          map->colors) * max_threads);

  viter_init (map, max_threads, average_color);
  {
    struct nearest_map *const n = nearest_init (map, fast_palette);
    hist_item *const achv = hist->achv;
    const int hist_size = hist->size;
    int j;

#pragma omp parallel for if (hist_size > 3000) \
            schedule(static) default(none) shared(average_color,callback) reduction(+:total_diff)
    for (j = 0; j < hist_size; j++) {
      float diff;
      unsigned int match =
          nearest_search (n, achv[j].acolor, achv[j].tmp.likely_colormap_index,
          min_opaque_val, &diff);
      achv[j].tmp.likely_colormap_index = match;
      total_diff += diff * achv[j].perceptual_weight;

      viter_update_color (achv[j].acolor, achv[j].perceptual_weight, map, match,
          omp_get_thread_num (), average_color);

      if (callback)
        callback (&achv[j], diff);
    }

    nearest_free (n);
  }
  viter_finalize (map, max_threads, average_color);

  return total_diff / hist->total_perceptual_weight;
}