gimp/app/base/hue-saturation.c

/* GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <glib-object.h>

#include "libgimpcolor/gimpcolor.h"
#include "libgimpmath/gimpmath.h"

#include "base-types.h"

#include "hue-saturation.h"
#include "pixel-region.h"


void
hue_saturation_init (HueSaturation *hs)
{
  GimpHueRange partition;

  g_return_if_fail (hs != NULL);

  hs->overlap = 0.0;

  for (partition = GIMP_ALL_HUES; partition <= GIMP_MAGENTA_HUES; partition++)
    {
      hs->hue[partition]        = 0.0;
      hs->lightness[partition]  = 0.0;
      hs->saturation[partition] = 0.0;
    }
}

void
hue_saturation_calculate_transfers (HueSaturation *hs)
{
  gint value;
  gint hue;
  gint i;

  g_return_if_fail (hs != NULL);

  /*  Calculate transfers  */
  for (hue = 0; hue < 6; hue++)
    for (i = 0; i < 256; i++)
      {
        /*  Hue  */
        value = (hs->hue[0] + hs->hue[hue + 1]) * 255.0 / 360.0;
        if ((i + value) < 0)
          hs->hue_transfer[hue][i] = 255 + (i + value);
        else if ((i + value) > 255)
          hs->hue_transfer[hue][i] = i + value - 255;
        else
          hs->hue_transfer[hue][i] = i + value;

        /*  Lightness  */
        value = (hs->lightness[0] + hs->lightness[hue + 1]) * 127.0 / 100.0;
        value = CLAMP (value, -255, 255);

        if (value < 0)
          hs->lightness_transfer[hue][i] = (guchar) ((i * (255 + value)) / 255);
        else
          hs->lightness_transfer[hue][i] = (guchar) (i + ((255 - i) * value) / 255);

        /*  Saturation  */
        value = (hs->saturation[0] + hs->saturation[hue + 1]) * 255.0 / 100.0;
        value = CLAMP (value, -255, 255);

        /* This change affects the way saturation is computed. With the
           old code (different code for value < 0), increasing the
           saturation affected muted colors very much, and bright colors
           less. With the new code, it affects muted colors and bright
           colors more or less evenly. For enhancing the color in photos,
           the new behavior is exactly what you want. It's hard for me
           to imagine a case in which the old behavior is better.
         */
        hs->saturation_transfer[hue][i] = CLAMP ((i * (255 + value)) / 255, 0, 255);
      }
}

void
hue_saturation (HueSaturation *hs,
                PixelRegion   *srcPR,
                PixelRegion   *destPR)
{
  const guchar *src, *s;
  guchar       *dest, *d;
  const gint    hue_thresholds[]    = { 21, 64, 106, 149, 192, 234, 255 };
  gint          alpha;
  gint          w, h;
  gint          r, g, b;
  gint          hue;
  gint          hue_counter;
  gint          secondary_hue       = 0;
  gboolean      use_secondary_hue   = FALSE;
  gfloat        primary_intensity   = 0.0;
  gfloat        secondary_intensity = 0.0;
  gfloat        overlap_hue         = (hs->overlap / 100.0) * 21;

  /*  Set the transfer arrays  (for speed)  */
  h     = srcPR->h;
  src   = srcPR->data;
  dest  = destPR->data;
  alpha = (srcPR->bytes == 4) ? TRUE : FALSE;

  while (h--)
    {
      w = srcPR->w;
      s = src;
      d = dest;

      while (w--)
        {
          r = s[RED];
          g = s[GREEN];
          b = s[BLUE];

          gimp_rgb_to_hsl_int (&r, &g, &b);

          hue = (r + (128 / 6)) / 6;

          for (hue_counter = 0; hue_counter < 7; hue_counter++)
            if (r < hue_thresholds[hue_counter] + overlap_hue)
              {
                gint  hue_threshold = hue_thresholds[hue_counter];

                hue = hue_counter;

                if (overlap_hue > 1.0 && r > hue_threshold - overlap_hue)
                  {
                    secondary_hue = hue_counter + 1;
                    use_secondary_hue = TRUE;
                    secondary_intensity =
                      (r - hue_threshold + overlap_hue) / (2.0 * overlap_hue);
                    primary_intensity = 1.0 - secondary_intensity;
                  }
                else
                  {
                    use_secondary_hue = FALSE;
                  }
                break;
              }

          if (hue >= 6)
            {
              hue = 0;
              use_secondary_hue = FALSE;
            }

          if (secondary_hue >= 6)
            secondary_hue = 0;

          if (use_secondary_hue)
            {
	      /*  find nearest hue on the circle
               *  between primary and secondary hue
               */
              gint diff;

              diff = hs->hue_transfer[hue][r] - hs->hue_transfer[secondary_hue][r];
              if (diff < -127 || diff >= 128)
                r = (gint) (hs->hue_transfer[hue][r] * primary_intensity +
                            (hs->hue_transfer[secondary_hue][r] + 255) * secondary_intensity) % 255;
              else
                r = hs->hue_transfer[hue][r] * primary_intensity +
                    hs->hue_transfer[secondary_hue][r] * secondary_intensity;

              g = hs->saturation_transfer[hue][g] * primary_intensity +
                  hs->saturation_transfer[secondary_hue][g] * secondary_intensity;
              b = hs->lightness_transfer[hue][b] * primary_intensity +
                  hs->lightness_transfer[secondary_hue][b] * secondary_intensity;
            }
          else
            {
              r = hs->hue_transfer[hue][r];
              g = hs->saturation_transfer[hue][g];
              b = hs->lightness_transfer[hue][b];
            }

          gimp_hsl_to_rgb_int (&r, &g, &b);

          d[RED]   = r;
          d[GREEN] = g;
          d[BLUE]  = b;

          if (alpha)
            d[ALPHA] = s[ALPHA];

          s += srcPR->bytes;
          d += destPR->bytes;
        }

      src  += srcPR->rowstride;
      dest += destPR->rowstride;
    }
}