despeckle.c

/* despeckle.c: Bitmap despeckler

   Copyright (C) 2001 David A. Bartold

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation; either version 2.1 of
   the License, or (at your option) any later version.

   This library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
   USA. */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif /* Def: HAVE_CONFIG_H */

#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <time.h>
#include "xstd.h"
#include "types.h"
#include "bitmap.h"
#include "despeckle.h"

/* Calculate Error - compute the error between two colors
 *
 *   Input parameters:
 *     Two 24 bit RGB colors
 *
 *   Returns:
 *     The squared error between the two colors
 */

static int
calc_error (unsigned char *color1,
            unsigned char *color2)
{
  int the_error;
  int temp;

  temp = color1[0] - color2[0];
  the_error = temp * temp;
  temp = color1[1] - color2[1];
  the_error += temp * temp;
  temp = color1[2] - color2[2];
  the_error += temp * temp;

  return the_error;
}


/* Calculate Error - compute the error between two colors
 *
 *   Input parameters:
 *     Two 8 bit gray scale colors
 *
 *   Returns:
 *     The squared error between the two colors
 */

static int
calc_error_8 (unsigned char *color1,
            unsigned char *color2)
{
  int the_error;
  int temp;

  temp = color1[0] - color2[0];
  the_error = temp * temp;

  return the_error;
}


/* Find Size - Find the number of adjacent pixels of the same color
 *
 * Input Parameters:
 *   An 24 bit image, the current location inside the image, and the palette
 *   index of the color we are looking for
 *
 * Modified Parameters:
 *   A mask array used to prevent backtracking over already counted pixels
 *
 * Returns:
 *   Number of adjacent pixels found having the same color
 */

static int
find_size (/* in */     unsigned char *index,
           /* in */     int    x,
           /* in */     int    y,
           /* in */     int    width,
           /* in */     int    height,
           /* in */     unsigned char *bitmap,
           /* in/out */ unsigned char *mask)
{
  int count;
  int x1, x2;

  if (y < 0 || y >= height ||
    mask[y * width + x] == 1 ||
    bitmap[3 * (y * width + x)    ] != index[0] ||
    bitmap[3 * (y * width + x) + 1] != index[1] ||
	bitmap[3 * (y * width + x) + 2] != index[2])
      return 0;

  for (x1 = x; x1 >= 0 &&
	bitmap[3 * (y * width + x1)    ] == index[0] &&
    bitmap[3 * (y * width + x1) + 1] == index[1] &&
	bitmap[3 * (y * width + x1) + 2] == index[2] &&
	mask[y * width + x] != 1; x1--) ;
  x1++;
  
  for (x2 = x; x2 < width &&
	bitmap[3 * (y * width + x2)    ] == index[0] &&
    bitmap[3 * (y * width + x2) + 1] == index[1] &&
	bitmap[3 * (y * width + x2) + 2] == index[2] &&
	mask[y * width + x] != 1; x2++) ;
  x2--;

  count = x2 - x1 + 1;
  for (x = x1; x <= x2; x++)
    mask[y * width + x] = 1;

  for (x = x1; x <= x2; x++)
    {
      count += find_size (index, x, y - 1, width, height, bitmap, mask);
      count += find_size (index, x, y + 1, width, height, bitmap, mask);
    }

  return count;
}


/* Find Size - Find the number of adjacent pixels of the same color
 *
 * Input Parameters:
 *   An 8 bit image, the current location inside the image, and the palette
 *   index of the color we are looking for
 *
 * Modified Parameters:
 *   A mask array used to prevent backtracking over already counted pixels
 *
 * Returns:
 *   Number of adjacent pixels found having the same color
 */

static int
find_size_8 (/* in */   unsigned char *index,
           /* in */     int    x,
           /* in */     int    y,
           /* in */     int    width,
           /* in */     int    height,
           /* in */     unsigned char *bitmap,
           /* in/out */ unsigned char *mask)
{
  int count;
  int x1, x2;

  if (y < 0 || y >= height ||
    mask[y * width + x] == 1 ||
    bitmap[(y * width + x)    ] != index[0])
      return 0;

  for (x1 = x; x1 >= 0 &&
	bitmap[(y * width + x1)    ] == index[0] &&
	mask[y * width + x] != 1; x1--) ;
  x1++;
  
  for (x2 = x; x2 < width &&
	bitmap[(y * width + x2)    ] == index[0] &&
	mask[y * width + x] != 1; x2++) ;
  x2--;

  count = x2 - x1 + 1;
  for (x = x1; x <= x2; x++)
    mask[y * width + x] = 1;

  for (x = x1; x <= x2; x++)
    {
      count += find_size_8 (index, x, y - 1, width, height, bitmap, mask);
      count += find_size_8 (index, x, y + 1, width, height, bitmap, mask);
    }

  return count;
}


/* Find Most Similar Neighbor - Given a position in an 8bit bitmap and a color
 * index, traverse over a blob of adjacent pixels having the same value.
 * Return the color index of the neighbor pixel that has the most similar
 * color.
 *
 * Input parameters:
 *   24 bit bitmap, the current location inside the image,
 *   and the color index of the blob
 *
 * Modified parameters:
 *   Mask used to prevent backtracking
 *
 * Output parameters:
 *   Closest index != index and the error between the two colors squared
 */

static void
find_most_similar_neighbor (/* in */     unsigned char *index,
                            /* in/out */ unsigned char **closest_index,
                            /* in/out */ int   *error_amt,
                            /* in */     int    x,
                            /* in */     int    y,
                            /* in */     int    width,
                            /* in */     int    height,
                            /* in */     unsigned char *bitmap,
                            /* in/out */ unsigned char *mask)
{
  int x1, x2;
  int temp_error;
  unsigned char *value, *temp;

  if (y < 0 || y >= height || mask[y * width + x] == 2)
    return;

  temp = &bitmap[3 * (y * width + x)];

  assert (closest_index != NULL);

  if (temp[0] != index[0] || temp[1] != index[1] || temp[2] != index[2])
    {
      value = temp;

      temp_error = calc_error (index, value);

      if (*closest_index == NULL || temp_error < *error_amt)
        *closest_index = value, *error_amt = temp_error;

      return;
    }

  for (x1 = x; x1 >= 0 &&
	bitmap[ 3 * (y * width + x1)    ] == index[0] &&
    bitmap[ 3 * (y * width + x1) + 1] == index[1] &&
	bitmap[ 3 * (y * width + x1) + 2] == index[2]; x1--) ;
  x1++;

  for (x2 = x; x2 < width &&
	bitmap[ 3 * (y * width + x2)    ] == index[0] &&
    bitmap[ 3 * (y * width + x2) + 1] == index[1] &&
	bitmap[ 3 * (y * width + x2) + 2] == index[2]; x2++) ;
  x2--;

  if (x1 > 0)
    {
      value = &bitmap[ 3 * (y * width + x1 - 1)    ];

      temp_error = calc_error (index, value);

      if (*closest_index == NULL || temp_error < *error_amt)
        *closest_index = value, *error_amt = temp_error;
    }

  if (x2 < width - 1)
    {
      value = &bitmap[ 3 * (y * width + x2 + 1)    ];

      temp_error = calc_error (index, value);

      if (*closest_index == NULL || temp_error < *error_amt)
        *closest_index = value, *error_amt = temp_error;
    }

  for (x = x1; x <= x2; x++)
    mask[y * width + x] = 2;

  for (x = x1; x <= x2; x++)
    {
      find_most_similar_neighbor (index, closest_index, error_amt, x, y - 1,
                                  width, height, bitmap, mask);
      find_most_similar_neighbor (index, closest_index, error_amt, x, y + 1,
                                  width, height, bitmap, mask);
    }
}


/* Find Most Similar Neighbor - Given a position in an 8bit bitmap and a color
 * index, traverse over a blob of adjacent pixels having the same value.
 * Return the color index of the neighbor pixel that has the most similar
 * color.
 *
 * Input parameters:
 *   8 bit bitmap, the current location inside the image,
 *   and the color index of the blob
 *
 * Modified parameters:
 *   Mask used to prevent backtracking
 *
 * Output parameters:
 *   Closest index != index and the error between the two colors squared
 */

static void
find_most_similar_neighbor_8 (/* in */   unsigned char *index,
                            /* in/out */ unsigned char **closest_index,
                            /* in/out */ int   *error_amt,
                            /* in */     int    x,
                            /* in */     int    y,
                            /* in */     int    width,
                            /* in */     int    height,
                            /* in */     unsigned char *bitmap,
                            /* in/out */ unsigned char *mask)
{
  int x1, x2;
  int temp_error;
  unsigned char *value, *temp;

  if (y < 0 || y >= height || mask[y * width + x] == 2)
    return;

  temp = &bitmap[(y * width + x)];

  assert (closest_index != NULL);

  if (temp[0] != index[0])
    {
      value = temp;

      temp_error = calc_error_8 (index, value);

      if (*closest_index == NULL || temp_error < *error_amt)
        *closest_index = value, *error_amt = temp_error;

      return;
    }

  for (x1 = x; x1 >= 0 &&
	bitmap[(y * width + x1)    ] == index[0]; x1--) ;
  x1++;

  for (x2 = x; x2 < width &&
	bitmap[(y * width + x2)    ] == index[0]; x2++) ;
  x2--;

  if (x1 > 0)
    {
      value = &bitmap[(y * width + x1 - 1)    ];

      temp_error = calc_error_8 (index, value);

      if (*closest_index == NULL || temp_error < *error_amt)
        *closest_index = value, *error_amt = temp_error;
    }

  if (x2 < width - 1)
    {
      value = &bitmap[(y * width + x2 + 1)    ];

      temp_error = calc_error_8 (index, value);

      if (*closest_index == NULL || temp_error < *error_amt)
        *closest_index = value, *error_amt = temp_error;
    }

  for (x = x1; x <= x2; x++)
    mask[y * width + x] = 2;

  for (x = x1; x <= x2; x++)
    {
      find_most_similar_neighbor_8 (index, closest_index, error_amt, x, y - 1,
                                  width, height, bitmap, mask);
      find_most_similar_neighbor_8 (index, closest_index, error_amt, x, y + 1,
                                  width, height, bitmap, mask);
    }
}


/* Fill - change the color of a blob
 *
 * Input parameters:
 *   The new color
 *
 * Modified parameters:
 *   24 bit pixbuf and its mask (used to prevent backtracking)
 */

static void
fill (/* in */     unsigned char *to_index,
      /* in */     int    x,
      /* in */     int    y,
      /* in */     int    width,
      /* in */     int    height,
      /* in/out */ unsigned char *bitmap,
      /* in/out */ unsigned char *mask)
{
  int x1, x2;

  if (y < 0 || y >= height || mask[y * width + x] != 2)
    return;

  for (x1 = x; x1 >= 0 && mask[y * width + x1] == 2; x1--) ;
  x1++;
  for (x2 = x; x2 < width && mask[y * width + x2] == 2; x2++) ;
  x2--;

  assert (x1 >= 0 && x2 < width);

  for (x = x1; x <= x2; x++)
    {
      bitmap[3 * (y * width + x)    ] = to_index[0];
      bitmap[3 * (y * width + x) + 1] = to_index[1];
      bitmap[3 * (y * width + x) + 2] = to_index[2];
      mask[y * width + x] = 3;
    }

  for (x = x1; x <= x2; x++)
    {
      fill (to_index, x, y - 1, width, height, bitmap, mask);
      fill (to_index, x, y + 1, width, height, bitmap, mask);
    }
}


/* Fill - change the color of a blob
 *
 * Input parameters:
 *   The new color
 *
 * Modified parameters:
 *   8 bit pixbuf and its mask (used to prevent backtracking)
 */

static void
fill_8 (/* in */   unsigned char *to_index,
      /* in */     int    x,
      /* in */     int    y,
      /* in */     int    width,
      /* in */     int    height,
      /* in/out */ unsigned char *bitmap,
      /* in/out */ unsigned char *mask)
{
  int x1, x2;

  if (y < 0 || y >= height || mask[y * width + x] != 2)
    return;

  for (x1 = x; x1 >= 0 && mask[y * width + x1] == 2; x1--) ;
  x1++;
  for (x2 = x; x2 < width && mask[y * width + x2] == 2; x2++) ;
  x2--;

  assert (x1 >= 0 && x2 < width);

  for (x = x1; x <= x2; x++)
    {
      bitmap[(y * width + x)    ] = to_index[0];
      mask[y * width + x] = 3;
    }

  for (x = x1; x <= x2; x++)
    {
      fill_8 (to_index, x, y - 1, width, height, bitmap, mask);
      fill_8 (to_index, x, y + 1, width, height, bitmap, mask);
    }
}


/* Ignore - blob is big enough, mask it off
 *
 * Modified parameters:
 *   its mask (used to prevent backtracking)
 */

static void
ignore (/* in */     int    x,
        /* in */     int    y,
        /* in */     int    width,
        /* in */     int    height,
        /* in/out */ unsigned char *mask)
{
  int x1, x2;

  if (y < 0 || y >= height || mask[y * width + x] != 1)
    return;

  for (x1 = x; x1 >= 0 && mask[y * width + x1] == 1; x1--) ;
  x1++;
  for (x2 = x; x2 < width && mask[y * width + x2] == 1; x2++) ;
  x2--;

  assert (x1 >= 0 && x2 < width);

  for (x = x1; x <= x2; x++)
    mask[y * width + x] = 3;

  for (x = x1; x <= x2; x++)
    {
      ignore (x, y - 1, width, height, mask);
      ignore (x, y + 1, width, height, mask);
    }
}


/* Recolor - conditionally change a feature's color to the closest color of all
 * neighboring pixels
 *
 * Input parameters:
 *   The color palette, current blob size, and adaptive tightness
 *
 *   Adaptive Tightness: (integer 1 to 256)
 *     1   = really tight
 *     256 = turn off the feature
 *
 * Modified parameters:
 *   24 bit pixbuf and its mask (used to prevent backtracking)
 *
 * Returns:
 *   TRUE  - feature was recolored, thus coalesced
 *   FALSE - feature wasn't recolored
 */

static at_bool
recolor (/* in */     double adaptive_tightness,
         /* in */     int    x,
         /* in */     int    y,
         /* in */     int    width,
         /* in */     int    height,
         /* in/out */ unsigned char *bitmap,
         /* in/out */ unsigned char *mask)
{
  unsigned char *index, *to_index;
  int error_amt;

  index = &bitmap[3 * (y * width + x)    ];
  to_index = NULL;
  error_amt = 0;

  find_most_similar_neighbor (index, &to_index, &error_amt,
                              x, y, width, height, bitmap, mask);

  /* This condition only fails if the bitmap is all the same color */
  if (to_index != NULL)
    {
      double temp_error;

      /* Adaptive */
      temp_error = calc_error (index, to_index);

      temp_error = sqrt (temp_error / 3.0);

      /*
       * If the difference between the two colors is too great,
       * don't coalesce the feature with its neighbor(s).  This prevents a
       * color from turning into its complement.
       */

      if (temp_error > adaptive_tightness)
        fill (index, x, y, width, height, bitmap, mask);
      else
        {
          fill (to_index, x, y, width, height, bitmap, mask);

          return true;
        }
    }

  return false;
}


/* Recolor - conditionally change a feature's color to the closest color of all
 * neighboring pixels
 *
 * Input parameters:
 *   The color palette, current blob size, and adaptive tightness
 *
 *   Adaptive Tightness: (integer 1 to 256)
 *     1   = really tight
 *     256 = turn off the feature
 *
 * Modified parameters:
 *   8 bit pixbuf and its mask (used to prevent backtracking)
 *
 * Returns:
 *   TRUE  - feature was recolored, thus coalesced
 *   FALSE - feature wasn't recolored
 */

static at_bool
recolor_8 (/* in */   double adaptive_tightness,
         /* in */     int    x,
         /* in */     int    y,
         /* in */     int    width,
         /* in */     int    height,
         /* in/out */ unsigned char *bitmap,
         /* in/out */ unsigned char *mask)
{
  unsigned char *index, *to_index;
  int error_amt;

  index = &bitmap[(y * width + x)    ];
  to_index = NULL;
  error_amt = 0;

  find_most_similar_neighbor_8 (index, &to_index, &error_amt,
                              x, y, width, height, bitmap, mask);

  /* This condition only fails if the bitmap is all the same color */
  if (to_index != NULL)
    {
      double temp_error;

      /* Adaptive */
      temp_error = calc_error_8 (index, to_index);

      temp_error = sqrt (temp_error / 3.0);

      /*
       * If the difference between the two colors is too great,
       * don't coalesce the feature with its neighbor(s).  This prevents a
       * color from turning into its complement.
       */

      if (temp_error > adaptive_tightness)
        fill_8 (index, x, y, width, height, bitmap, mask);
      else
        {
          fill_8 (to_index, x, y, width, height, bitmap, mask);

          return true;
        }
    }

  return false;
}


/* Despeckle Iteration - Despeckle all regions smaller than cur_size pixels
 *
 * Input Parameters:
 *   Current blob size, maximum blob size
 *   for all iterations (used to selectively recolor blobs), and adaptive
 *   tightness
 *
 * Modified Parameters:
 *   The 24 bit pixbuf is despeckled
 */

static void
despeckle_iteration (/* in */     int    level,
                     /* in */     double adaptive_tightness,
                     /* in */     int    width,
                     /* in */     int    height,
                     /* in/out */ unsigned char *bitmap)
{
  unsigned char *mask;
  int    x, y;
  int    i;
  int    current_size;
  int    tightness;

  for (i = 0, current_size = 1; i < level; i++, current_size *= 2)
    tightness = (int) (256 / (1.0 + adaptive_tightness * level));

  mask = (unsigned char *) calloc (width * height, sizeof(unsigned char));
  for (y = 0; y < height; y++)
    {
      for (x = 0; x < width; x++)
        {
          if (mask[y * width + x] == 0)
            {
              int size;

              size = find_size (&bitmap[3 * (y * width + x)], x, y,
                                width, height, bitmap, mask);

              assert (size > 0);

              if (size < current_size)
                {
                  if (recolor (tightness,
                               x, y, width, height,
                               bitmap, mask))
                    x--;
                }
              else
                ignore (x, y, width, height, mask);
            }
        }
    }

  free (mask);
}


/* Despeckle Iteration - Despeckle all regions smaller than cur_size pixels
 *
 * Input Parameters:
 *   Current blob size, maximum blob size
 *   for all iterations (used to selectively recolor blobs), and adaptive
 *   tightness
 *
 * Modified Parameters:
 *   The 8 bit pixbuf is despeckled
 */

static void
despeckle_iteration_8 (/* in */   int    level,
                     /* in */     double adaptive_tightness,
                     /* in */     int    width,
                     /* in */     int    height,
                     /* in/out */ unsigned char *bitmap)
{
  unsigned char *mask;
  int    x, y;
  int    i;
  int    current_size;
  int    tightness;

  for (i = 0, current_size = 1; i < level; i++, current_size *= 2)
  tightness = (int) (256 / (1.0 + adaptive_tightness * level));

  mask = (unsigned char *) calloc (width * height, sizeof(unsigned char));
  for (y = 0; y < height; y++)
    {
      for (x = 0; x < width; x++)
        {
          if (mask[y * width + x] == 0)
            {
              int size;

              size = find_size_8 (&bitmap[(y * width + x)], x, y,
                                width, height, bitmap, mask);

              assert (size > 0);

              if (size < current_size)
                {
                  if (recolor_8 (tightness,
                               x, y, width, height,
                               bitmap, mask))
                    x--;
                }
              else
                ignore (x, y, width, height, mask);
            }
        }
    }

  free (mask);
}


/* Despeckle - Despeckle an 8/24 bit image
 *
 * Input Parameters:
 *   Color palette, current blob size, and the despeckling level
 *
 *   Despeckling level: Integer from 0 to ~20
 *     0 = perform no despeckling
 *     An increase of the despeckling level by one doubles the size of features
 *
 *   Adaptive tightness:
 *     0 = Turn it off (whites may turn black and vice versa, etc)
 *     3 = Good middle value
 *     8 = Really tight
 *
 * Modified Parameters:
 *   The 24 bit pixbuf is despeckled
 */

void
despeckle (/* in/out */ bitmap_type *bitmap,
           /* in */     int          level,
           /* in */     at_real      tightness,
	   at_exception_type * excep)
{
  int i;
  int planes;

  planes = BITMAP_PLANES (*bitmap);

  assert (tightness >= 0.0 && tightness <= 8.0);
  assert (level >= 0 && level <= 20);

  if (planes == 3) {
  for (i = 0; i < level; i++)
    despeckle_iteration (i, tightness, BITMAP_WIDTH (*bitmap),
    BITMAP_HEIGHT (*bitmap), BITMAP_BITS(*bitmap));
  }
  else if (planes == 1) {
  for (i = 0; i < level; i++)
    despeckle_iteration_8 (i, tightness, BITMAP_WIDTH (*bitmap),
    BITMAP_HEIGHT (*bitmap), BITMAP_BITS(*bitmap));
  }
  else
    {
      LOG1 ("despeckle: %u-plane images are not supported", planes);
      at_exception_fatal(excep, "despeckle: wrong plane images are passed");
      return;
    }

}