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contnorm.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 a contrast normalization on an image.  The mean   */
/*   graylevel is shifted, and the graylevels are stretched to result in      */
/*   the specified standard deviation from the mean.                          */
/*                                                                            */
/*----------------------------------------------------------------------------*/
/*-Interface Information------------------------------------------------------*/
void
CONTNORM (IMAGE * in,           /*  I   Pointer to the input image.                           */
          PIXEL mean,           /*  I   Mean graylevel in the output image.                   */
          double sigma,         /*  I   Standard deviation in the output image.               */
          short inc,            /*  I   Line and pixel subsample increment.                   */
          IMAGE ** out          /*  O   Address of a pointer to the output image.             */
          /*      The input image may be overwritten (out = &in).       */
/*----------------------------------------------------------------------------*/
  )
{
  register short i, j, k;
  char msg[SLEN];
  double oldsigma, gain, bias;
  PIXEL sum, sumsq, oldmean;

  if (TIMES)
    TIMING (T_CONTNORM);
  if (NAMES)
    {
      MESSAGE ('I', "");
      MESSAGE ('I', "CONTNORM");
      MESSAGE ('I', "");
      sprintf (msg, " Input image:                          %s", in->text);
      MESSAGE ('I', msg);
      sprintf (msg, " Graylevel mean:                     %12.4e", mean);
      MESSAGE ('I', msg);
      sprintf (msg, " Graylevel standard deviation:       %12.4e", sigma);
      MESSAGE ('I', msg);
      sprintf (msg, " Line and pixel subsample increment:   %d", inc);
      MESSAGE ('I', msg);
      MESSAGE ('I', " ...............");
    }

  /* check input */
  if (!CHECKIMG (in))
    {
      MESSAGE ('E', " Can't identify image.");
      goto the_end;
    }
  else if (inc <= 0)
    {
      MESSAGE ('E', " Subsample increment must be greater than zero.");
      goto the_end;
    }

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

  /* compute statistics */
  for (sum = sumsq = 0.0, i = 0; i < in->nbnd; i++)
    {
      for (j = 0; j < in->nlin; j += inc)
        {
          for (k = 0; k < in->npix; k += inc)
            {
              sum += in->data[i][j][k];
              sumsq += in->data[i][j][k] * in->data[i][j][k];
            }
        }
    }
  oldmean =
    (PIXEL) ((double) sum /
             ((double) in->nbnd *
              (double) (in->nlin / inc +
                        (in->nlin % inc ? 1 : 0)) * (double) (in->npix / inc +
                                                              (in->npix %
                                                               inc ? 1 :
                                                               0))));
  oldsigma =
    sqrt ((double) sumsq /
          ((double) in->nbnd *
           (double) (in->nlin / inc +
                     (in->nlin % inc ? 1 : 0)) * (double) (in->npix / inc +
                                                           (in->npix %
                                                            inc ? 1 : 0))) -
          (double) oldmean * (double) oldmean);

  /* calculate parameters for stretch */
  gain = sigma / oldsigma;
  bias = (double) mean - gain * (double) oldmean;

  /* perform stretch */
  for (i = 0; i < in->nbnd; i++)
    {
      for (j = 0; j < in->nlin; j++)
        {
          for (k = 0; k < in->npix; k++)
            {
              (*out)->data[i][j][k] =
                (PIXEL) (gain * (double) in->data[i][j][k] + bias);
            }
        }
    }

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

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