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median.c

Go to the documentation of this file.

#include        "sadie.h"

/*-Copyright Information------------------------------------------------------*/
/* Copyright (c) 1988 by the University of Arizona Digital Image Analysis Lab */
/*----------------------------------------------------------------------------*/
/*-General Information--------------------------------------------------------*/
/*                                                                            */
/*   This function performs median filtering of an image.                     */
/*                                                                            */
/*----------------------------------------------------------------------------*/
/*-Interface Information------------------------------------------------------*/
void
MEDIAN (IMAGE * in,             /*  I   Pointer to the input image.                           */
        short jsize,            /*  I   Number of lines in the median window.                 */
        short ksize,            /*  I   Number of pixels/line in the median window.           */
        IMAGE ** out            /*  O   Address of a pointer to the output image.             */
/*----------------------------------------------------------------------------*/
  )
{
  register short i, j, k, l, m, count, index, jstart, jend, kstart, kend,
    jover = (jsize - 1) / 2, kover = (ksize - 1) / 2;
  char msg[SLEN];
  double pinc, psum;
  PIXEL med, *list = 0;

  if (TIMES)
    TIMING (T_MEDIAN);
  if (NAMES)
    {
      MESSAGE ('I', "");
      MESSAGE ('I', "MEDIAN");
      MESSAGE ('I', "");
      sprintf (msg, " Input image:           %s", in->text);
      MESSAGE ('I', msg);
      sprintf (msg, " Window size: lines:    %d", jsize);
      MESSAGE ('I', msg);
      sprintf (msg, "              pixels:   %d", ksize);
      MESSAGE ('I', msg);
      MESSAGE ('I', " ...............");
    }

  /* check input */
  if (!CHECKIMG (in))
    {
      MESSAGE ('E', " Can't identify image.");
      goto the_end;
    }
  else if (jsize <= 0 || jsize % 2 == 0)
    {
      MESSAGE ('E',
               " Number of lines in the median window must be an odd number greater than zero.");
      goto the_end;
    }
  else if (jsize > in->nlin)
    {
      MESSAGE ('E',
               " Image line size must be equal to or greater than window size.");
      goto the_end;
    }
  else if (ksize <= 0 || ksize % 2 == 0)
    {
      MESSAGE ('E',
               " Number of pixels/line in the median window must be an odd number greater than zero.");
      goto the_end;
    }
  else if (ksize > in->npix)
    {
      MESSAGE ('E',
               " Image pixel size must be equal to or greater than window size.");
      goto the_end;
    }

  /* create image of appropriate size */
  if (!CHECKIMG (*out))
    GETMEM (in->nbnd, in->nlin, in->npix, out);
  if (!*out)
    goto the_end;

  /* allocate space for 1-D array */
  if (!(list = (PIXEL *) malloc (jsize * ksize * sizeof (PIXEL))))
    {
      MESSAGE ('E', " Memory request failed.");
      goto the_end;
    }

  /* initialize progress indicator */
  if (LINES && !PROGRESS (psum = 0.0))
    goto the_end;
  pinc = 1.0 / (double) in->nbnd / (double) in->nlin;

  /* put pixels inside window into array */
  for (i = 0; i < in->nbnd; i++)
    {
      for (j = 0; j < in->nlin; j++)
        {
          jstart = max (0, j - jover);
          jend = min (j + jover, in->nlin - 1);
          for (k = 0; k < in->npix; k++)
            {
              kstart = max (0, k - kover);
              kend = min (k + kover, in->npix - 1);
              for (count = 0, l = jstart; l <= jend; l++)
                {
                  for (m = kstart; m <= kend; m++)
                    {
                      list[count++] = in->data[i][l][m];
                    }
                }

              /* compute median */
              for (l = 0; l < (count + 1) / 2; l++)
                {
                  med = list[index = l];
                  for (m = l + 1; m < count; m++)
                    {
                      if (med > list[m])
                        med = list[index = m];
                    }
                  list[index] = list[l];
                }
              (*out)->data[i][j][k] = med;
            }
          if (LINES && !PROGRESS (psum += pinc))
            goto the_end;
        }
    }

the_end:
  if (list)
    free (list);
  if (TIMES)
    TIMING (T_EXIT);
}

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